April 2004 (#101):

or read TWDT


The Mailbag

HELP WANTED : Article Ideas
Submit comments about articles, or articles themselves (after reading our guidelines) to The Editors of Linux Gazette, and technical answers and tips about Linux to The Answer Gang.

installing mandrake 10.0

Wed, 24 Mar 2004 20:58:16 +0000
spb (t14497867 from netscape.net)

Greetings I installedd disks 1 and 2 linux mandrake 10.0 as an upgrade to my linux mandrake 9.2, immediately all froze onsgreen . Need an answer- my 9.2 works ok. thanks.

Wanted point number 1: clearer requests. -- Heather
[Thomas] Hi, unfortunately I often have trouble decyphering all that information that you poured into such a well thought out e-mail. You obviously spent a lot of time thinking about your problem, listing all the symptoms, etc. You should give yourself credit for it.
Here's a tip though:
http://linuxgazette.net/tag/ask-the-gang.html
Oh, if you send HTML e-mail to this list again, there's a high chance you'll get ignored. Seriously we need more information about what id freezing, whether or not you completed your upgrade, whether or not your kernel boots....etc.... Otherwise, how can we help you?

Greetings answer gang, I reply to your mail yesterday.

Alas, he still sent text+html email. Wanted point number 2: I can't use your webmail's HTML folks. Don't waste the bandwidth (about 3x the space!) sending those extra bits. -- Heather

The computer using today has Microsft ME os, I cannot send any info to you from my linux PC, as when I loaded the upgrade mandrake 10.0 on top of my Mandrake 9.2-( purchased from Mandrake central USA} when after some time(I thought it had installed 10.0) it returned to the welcome desktop screen, from there it is completely frozen, the mouse, the arrow keys , tab key and function keys, so restart many times( by power off and on only,my only option at the moment} I arrive each time to this situation, I cannot get to bios settings to change device priority for startup. to use a boot disk or floppy.

[THomas] Presumably you managed to boot off of a CD just fine. In that case, I suggest (no, I urge you) to download knoppix [1] and boot from that. If you have not the facilities to burn CDs, then find someone who can. Why exactly can't you access your BIOS?
That's where you come in, dear readers :D -- Heather

I purchased Mandrake 10.0 from Linuz.org in USA they sent two cd's by airmail without any other info except invoice.

[Thomas] Also, as this is Mandrake, I suggest when you next boot into Linux, you issue:
linux 3
(at the LILO/Grub prompt) so that you're forced into a text-only mode. Hoipefully you should be able to report back to us whether you can login or not, and whether your keyboard is still locked, etc.

Please advise a good Linux Tutorial book for home users, I am not IT boffin thank you .spbramwell.

[Thomas] The book I used wqas "Running Linux", Matt Walsh, et al. Publsihed by O'reilly. You'll find it on amazon no problems.
[Heather] The book I got started with was "Unix as a Second Language" by Sobell, which has now become several books, for different flavors of UNIX. The current one of the Linux flavor shows a penguin belly flopping down a snow bank :) It also got renmaed though ... the name escapes me at this hour ... Any of the series though, will definitely make your starting out a little more fun.
Readers: more good book suggestions?

More Cool Answers

Wed, 31 Mar 2004 11:35:38 -0800
Heather Stern (The Answer Gang's Editor Gal)

There's some dark chocolate waiting in the Answer Gang's back lounge for new folk inclined to send in their good tips or a nice long chat about how some useful part of Linux really works. You don't have to join the TAG list either -- just send your bits in to tag@linuxgazette.net.

GENERAL MAIL

My sig, and Linux Gazette... :)

Mon, 8 Mar 2004 02:18:52 -0800 (PST)
Dave Bechtel (kingneutron from yahoo.com)
Question by carla (carla from bratgrrl.com)

re: http://linuxgazette.net/100/lg_mail.html

Glad you liked my .sig. :) I have fond feelings for the original Muppets, including the Sesame Street ones. Even have some mpeg's of them, such as two aliens and a hippie singing "Manomonot" on the Muppet Show, as well as the Intro to the Fraggle Rock show -- in Swedish (I think - it's called "Fragglarna".)

IIRC, I saw a similar 1337 .sig on Slashdot or somewhere a few years ago, and adapted it for the Muppets. I got a real charge out of seeing it posted in LG.Net (twice now, no less!) and the response it generated. LOL.

;-)

(You have my permission to publish this letter or share with LG.Net colleagues if you see fit.)

Best wishes. (And LG, please tell Thomas Adam I'm sorry for being so short with him. I was going through a bad time, and ended up having to move in order to get away from the situation.)

Linux, making Sesame Street more fun... -- Heather

[cc] Looking for Stephen Bint

Thu, 1 Apr 2004 00:20:47 -0500
Ben Okopnik (LG Technical Editor)
Question by Heather (star from starshine.org)

Hello Heather,

Hi, Gianfranco -

I'm not Heather, but I'm the fellow who receives mail at the editor@ address these days. :)

I lost contact to Stephen Bint who used to be a member in the Answer Gang. Messages to him are bouncing.

Please be so kind and let him know that he should get in touch with me.

Thank you very much.

-- gianfranco accardo gfa2c gmx.net

Stephen Bint was never a member of The Answer Gang; he wrote a couple of articles for LG. I'm afraid we have no way to contact him beyond his email, and given his own statement of his lifestyle:

Stephen is a homeless Englishman who lives in a tent in the woods. He eats out of bins and smokes cigarette butts he finds on the road. Though he once worked for a short time as a C programmer, he prefers to describe himself as a "keen amateur".

- losing track of him is not an unlikely occurence. I'll CC Heather on this, but I doubt that she'll be able to help you any more than I could.

Presuming that he occasionally sneaks into a cybercafe to read LG and write an article now and then, we'll pub the request in the Gazette and see if he responds. To which end, I've left gianfranco's address visible. I apologize in advance if the spambeasts find it too. :( -- Heather
GAZETTE MATTERS

Back issues of lg as pdbs

Mon, 1 Mar 2004 11:56:12 -0000 (GMT)
Alan Pope (alan from popey.com)

Hi all,

I spoke with Thomas on IRC last night about this but it was late and I'm not sure I made myself clear.

I'd like to be able to read the lg on my palm device. Now I know I can click the TWDT link on the front page of the site, whereupon some magic cgi-bin foo generates a pdb file for me to download. I guess this is taking the text version of TWDT and generating the pdb on the fly?

My question is this. That process is fine and dandy for the current release, but I'd like to read older issues on my palm. Can the pdbs be made available on the ftp site?

[Sluggo] linuxgazette.net doesn't have an FTP site. It now uses a portion of the website for tarball downloads.
The biggest issue with putting Palm-format files in that directory is they will be picked up by the mirrors. We'd have to check with the mirrors whether the bandwidth/size would be a hardship. We also look at how widely used the files would be. The tarballs can be used on any platforms with any OS. Palm files work only with certain brands of palmtops and exclude everything else.
[Thomas] Hence I agree that generating them on-the-fly (talking of that, congratulations, Ben!!) is a far better thing to do.
[Ben] Actually, AFAIK, the Palm Reader is available for several different platforms; certainly for Wind0ws, WinCE and both of the Linux distros made for the iPaq. However, I agree that we shouldn't clutter our tarballs with these things; that was the point of doing this stuff "on the fly" for the folks who want it.

I could convert the files myself I suppose which would probably involve lynxing the TWDT text version of the file and then using "some tool" to generate the pdb from the .txt file. However I just wondered if as that particular wheel has already been invented, it might save some work?

Cheers, Al.

[Ben] Nope, there's nothing set up. I'd suggest grabbing "bibelot" from Freshmeat and converting whichever TWDT you'd like. Here's the simplest way I can think of:
lynx -dump -nolist http://linuxgazette.net/issueXX/TWDT.html|bibelot -f -t twdtXX.pdb
where XX is the number of the issue. If you wanted to do a bunch of them in one shot, you could even do a "for" loop: 
for n in `seq $first $last`; do ... done
where $first and $last would delimit the range of issues that you want to convert.

Sure, and I wasn't suggesting that you should add pdb to the tarball or the ftp server, just asking if the process is already there to generate pdbs, why not make it available for back issues too?

Hence me saying why reinvent the wheel.

I don't have a problem downloading the TWDTs and converting them, just thought it would be easier to use whats already there.

Cheers, Al.

This page edited and maintained by the Editors of Linux Gazette
HTML script maintained by Heather Stern of Starshine Technical Services, http://www.starshine.org/

Published in Issue 101 of Linux Gazette, April 2004


More 2 Cent Tips!

See also: The Answer Gang's Knowledge Base and the LG Search Engine

Pushing Files To Multiple Hosts

Sun, 07 Mar 2004 20:46:45 -0500
Sean Johnson (sean from gutenpress.org)

While it might be overkill for your situation, this is a perfect place to use cfengine ( http://www.cfengine.org ).

Perhaps I should write up an article for Linux Gazette? :)

Cheers,

Sean

[Thomas] You're more than welcome to do so. Author submission guidelines can be found in the FAQ, found here:
http://linuxgazette.net/faq/author.html

Connecting Mac OS9/10 to a Linux Samba Domain

Thu, 05 Feb 2004 12:22:12 +0300
Thomas Adam, Breen Mullins (The LG Answer Gang)
Question by JG Nasser Olwero (jgnasser from mpala.org)

I run Samba 2.2.3a on RH Linux 7.3 as the Domain Controller. I have all my Windows clients connecting fine to it but have trouble with Mac clients, no idea how to log them on. I also attempted to have the Mac client connect to the Linux POP3 and SMTP server (Sendmail) to no avail probably because the Mac is not welcome on the network. I am connecting the Mac using wired ethernet to a Network switch.

[Thomas] You need to ensure that you're using the 'appletalk' protocol. This has to be enabled in the kernel. There are also userspace programs that are needed for this.
http://ftp.linux.org.uk/pub/linux/appletalk
might be of interest.
Hope That Helps
[Breen] You don't use AppleTalk to connect to a POP or SMTP server. That's pure TCP/IP.
If we're talking about a Mac OS X client, that comes with Windows filesharing built in. Classic Mac OS is of course a different problem.
Actually, MacOS X knows how to speak Samba/mswin sharing now too; their client side tool is called DAVE, and it used to be third party software for MacOS 9. If you want to install Mac style sharing on your Linux box, the app you're looking for is called netatalk. I used it years ago and it was a breeze to setup - had 'em working faster than their mswin cousins in the same office. -- Heather
[Breen] If you're using OS X you can call up a connect dialog with Cmd-K and enter the address smb://<ip_of_server>. You'll need an IP address, of course -- check your network preferences pane to make sure.
Beyond that, you're probably looking at a Mac client issue. You might try asking for help at a Mac specific site. (I recommend http://forums.macosxhints.com, if you're using X.)

CDROM not seen by RH9

Thu, 11 Mar 2004 16:29:46 -0500
Thomas Adam (The LG Weekend Mechanic)
Question by Joseph Lalingo (ah300 from torfree.net)

Hi,

I installed RedHat Linux 9 via the cd-rw, successfully, but the cdrom was not seen. I know the cdrom is still connected internally as I haven't interfered with the system's insides (which came with a a cdrom and cd-rw) internally. The cd-rw is understood to be the cdrom and there is now NO /mnt/cdrom1 but there IS a /mnt/cdrom.

The cdrom door does not open, yet the light of the cdrom is on.

Joe

[Thomas] "The lights are on but there's no one home". /mnt/cdrom is the mount-point location of your cdrom drive. It is arbitrary and you can use anything you like. These are defined (or should be) in /etc/fstab.
If you look in that file, you should have a line similar to: 
/dev/cdrom      /cdrom          iso9660 ro,user,noauto          0       0
Here, /dev/cdrom is in turn a symlink that points to my main cdrom device: /dev/hdd. This then gets mounted to /cdrom, when I issue the command: 
mount /cdrom
I suspect your troubles come from you missing an entry in /etc/fstab. If you wanted to mount the second drive as /mnt/cdrom1, then look at the existing line in the /etc/fstab file, and modify it to reflect the new drive.
The device name (/dev/xxx) can be got from viewing: 
dmesg | less

In Short, Dig This

Wed, 31 Mar 2004 01:45:38 -0800
Jim Dennis (the LG Answer Guy)

Possibly there's not a sysadmin around who hasn't needed to do a host lookup now and then, to make sure they know what addresses are really being found when a DNS lookup is made.

nslookup is deprecated, host can be confusing, dig is the nice tool for the job - regardless of attempts to claim it is old too, it will be around a long time. But who really wants to get a long listing full of semicolon comments and things? 

; <<>> DiG 9.2.3rc4 <<>> linuxgazette.net
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 605
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;linuxgazette.net.		IN	A

;; ANSWER SECTION:
linuxgazette.net.	86400	IN	A	64.246.26.120

;; AUTHORITY SECTION:
linuxgazette.net.	86400	IN	NS	ns1.linuxmafia.com.
linuxgazette.net.	86400	IN	NS	ns1.genetikayos.com.

;; ADDITIONAL SECTION:
ns1.linuxmafia.com.	61864	IN	A	198.144.195.186
ns1.genetikayos.com.	61864	IN	A	64.246.26.120

;; Query time: 153 msec
;; SERVER: 216.240.40.162#53(216.240.40.162)
;; WHEN: Wed Mar 31 01:39:18 2004
;; MSG SIZE  rcvd: 144

Unless I'm tracking the path of authority rather than just checking the address, I don't care either. 

(jimd@phobos) ~$ dig +short a linuxgazette.net
64.246.26.120

Short, sweet, and to the point. Replace "a" with "mx" or "ns" as you please, but this is a lot handier for scripting; I don't have to invoke my talent for awk and grep one-liners on DNS checks anymore.

DNS proxy/cache (Tip)

Tue, 16 Mar 2004 00:11:33 +0100
Karl-Heinz Herrmann (kh1dump from khherrmann.de)

Hi,

I had an annoying little problem: My home network has grown to 3 PC's -- one directly on the phone line, the others connected via WLAN. Usually I would pick one dial-up provider and stick with that. Unfortunately the German ISP's are a big mess of call-by call providers with constantly changing tarifs.

The directly connected box is only the dial-in and firewall/NAT Router, the other two are my Laptop and desktop.

The annoying problem: Everytime I change the provider I had to change the resolv.conf on all systems according to the new nameservers as transmitted via [i]ppp protocol.

My solution: dproxy
http://dproxy.sourceforge.net

It serves as a proxy/cache for DNS lookups. It uses regular sys-calls for namelookups and reacts instantly (no kill -HUP or similar) to new entries in /etc/resolv.conf. This is on the router of course and everytime pppd changes the resolv.conf for the new provider it simply uses the new values.

The other two machines have the router as the nameserver and always get the correct information (even offline, so a connection is of course not possible). No manual changing anymore.

K.-H.

Making filenames lowercase

Wed, 31 Mar 2004 10:05:38 -0500
Ben Okopnik (LG Technical Editor)

Sometimes, despite our best eforts with "unzip -L", we end up with a bunch of files the names of which are ALL IN CAPS. The easy way to deal with these is with a simple utility that I call "lc". (Also, should you ever need such a thing, creating a complementary "uc" would be an obvious modification.) 

#!/usr/bin/perl -w
# Created by Ben Okopnik on Fri Jul 25 09:13:22 EDT 2003

die "Usage: ", $0 =~ /([^\/]+)$/, " <FILE[S]_TO_LOWERCASE>\n" unless @ARGV;

rename $_, lc for @ARGV

Note that you can specify multiple files or even shell wildcards at the command line; it's perfectly happy to chew on whatever you supply.

measuring the temperature in your computer room

Wed, 17 Mar 2004 13:12:23 -0800
Yan-Fa Li (yanfali from best.com)

Hi,

I've found a useful side effect of running smartd on my drives at home which I've used for a while now to monitor the temperature in my apartment. A lot of newer IDE drives, especially IBM/Hitachi's and SCSI hard disks monitor the drive temperature. I've found this to be a useful way to figure out how hot it is in my computer room at home :D

Assuming you've already installed smartmontools, this was tested with version 5.26: 

# smartctl -a /dev/hda | grep 194
194 Temperature_Celsius     0x0002   161   161   000    Old_age
Always       -       34 (Lifetime Min/Max 20/37)

As you can see the drive is a toasty 34 degrees celsius. Of about 5-7 degrees above ambient, it's about 27-29C or 80-85F in that room right now. Not great for the equipment but survivable. Anyway, not terribly useful, but interesting nonetheless :D

Yan

Troubleshooting mail delivery

Thu, 1 Apr 2004 22:33:59 -0500
Ben Okopnik (LG Technical Editor)

There are times when the mail just won't go through, for any of a host of reasons. Your ISP's server may be down, your own mail programs don't work, whatever - and of course, this happens at the most critical times, "when it absolutely, positively has to be there." Well, assuming that your recipient's mail server is working, you can bypass most of the chain - at least your end of it. This can also be a good testing tool. It lacks a few refinements (e.g., there's no subject and the address you supply is actually used as the normally hidden "From" header rather than the friendlier and visible "From:"), but it will at least get the content across. 

ben@Fenrir:~/Docs$ telnet badabing.com 25
Trying badabing.com...
Connected to badabing.com.
Escape character is '^]'.
220 badabing.com ESMTP Postfix (Debian/GNU)
HELO myserver.net
250 badabing.com
MAIL FROM: me@myserver.net
250 Ok
RCPT TO: joe@badabing.com
250 Ok
DATA
354 End data with <CR><LF>.<CR><LF>

Hi, Joe - it's me!

.
250 Ok: queued as D1F8F160B4
QUIT

To recap - I connected to port 25 (SMTP) at badabing.com, identified my server via HELO ("hello"), to which the server responded with its own name. I then told it who the MAIL was FROM: and who the recipient (RCPT) is supposed to be, and asked it to stand by for the actual DATA, which it told me to end with a return, a period, and a return. When I was done, I typed "QUIT" to exit.

This is not for everyday use, but can be a very handy tool for those times when you've just got to get your mail across despite problems.

vmlinuz from when and where?

Wed, 31 Mar 2004 01:45:38 -0800
Heather Stern (The Answer Gang's Editor Gal)

In my consulting I find myself running into an awful lot of systems booting off of 'vmlinuz' in the root directory. What kernel is that? How the heck would I know?

I'll tell you how I ask it :D 

[root@somebox] /# strings vmlinuz | grep 200
2.6.0-test7-1-386 (herbert@gondolin) #1 Sun Oct 12 10:29:56 EST 2003

Why does this work? Because now that we're a few years into the century, nearly all the kernels contain something with a year 2000 or later, and we'll have 200n year numbers for a while yet. On an older system, try 199 - Linux isn't old enough to have kernels from 1980 unless someone is playing serious games with their clock. You could probably look for the @ sign, but chances are too good of finding one alone somewhere in the binary portion of the code.

This page edited and maintained by the Editors of Linux Gazette
HTML script maintained by Heather Stern of Starshine Technical Services, http://www.starshine.org/

Published in Issue 101 of Linux Gazette, April 2004


The Answer Gang

(?)
By Jim Dennis, Ben Okopnik, Dan Wilder, Breen, Chris, and... (meet the Gang) ... the Editors of Linux Gazette... and You!
(?)


We have guidelines for asking and answering questions. Linux questions only, please.
We make no guarantees about answers, but you can be anonymous on request.
See also: The Answer Gang's Knowledge Base and the LG Search Engine


Contents:

¶: Greetings From Heather Stern
(?)Compile on one, run on another machine
(?)Dedicated Linux application
(?)Diagnosing a Linux crash
(?)I blew out Fedora with yum and 2.62
(?)2c tip: filtering in-place
(?)framebuffer colors
(?)Mirror 2 web servers

(¶) Greetings from Heather Stern

Greetings, folks, and welcome to the world of The Answer Gang. It's been a rough and tumble time here... I've got some hardware in a shambles. It's just not my week. Just looking at all these scattered parts makes me wonder if I could build a robot out of them. I've got enough backups I've certainly my pick of linux flavors...

Then some folks in an IRC channel got into discussing what sort of mayhem we would see if various window managers were thrown into a gladiatorial arena and forced to duke it out, mano a mano, claw to saw. "Fight! Fight!" cried our Weekend Mechanic -- as he cheerfully added parts to the house favorite -- and the battle was on.

WM-bot Wars

In our first round of the competition, we have the little guys. Heck, you might have even heard of some of them. Aren't they so cute! Minimal is the name of the game here. Let's weigh in, the advantage is they're light, the disads are what features they left out - the underpower crowd roars for these underdogs - here you have 'em folks:

The fight begins, with these and crowds of other small fry swarming to the freshmeat. Amaterus makes a pretty good start but it has a menu - just a sucky one. Someone hops a pogo stick and virtual desktops sprout. Apps being executed everywhere. A pypanel confers, Oroborus nearly trapped against the obscurity wall when MacOSX rescues it. And the first round goes to the happy Blackbox family, including hacked, open, and flux box for creative menu tricks ranking recently used apps.

The bell rings and we clear out a few smoking ruins - now for the midsize mayhem.

WindowMaker wades in - or is that widowmaker - docks his jaws around AfterStep. Tiny Tom's wm escapes the system spikes, but Claude has the extra edge. IceWM is looking cool until he hits the arena's flame trap "I wanna look like..." but won't fall for that - escapes the pit! Menus click, swap thrashes, and catlike fvwm takes control of the mouse, scripting rings around the others.

Now for a page from the masters. We know those flames are tough, and it's time to let the survivors here get a chance to commit before the next round... the big noisy battle of them all... Desktops.

Gnome and KDE both extend their hints against the competition, crushing smaller opponents. Enlightenment upgrades to 16.6 and stands its ground. FVWM laughs and sprouts modules to extend itself, while fast light wm joins it in pushing the brutes into the arena's OOM killer. Parts are flying everywhere! Chipping through the armor, flames are getting through ... ooh! FVWM escapes by shedding its modules again, while K is trapped. Something's bound to overload... K's gears grind slowly to a halt, while Gnome has the metacity to pick on E's incomplete brother which valiantly struggles to code up href="http://enlightenment.org/pages/news.html">new features before timeout. XFce zooms into the fray -- "wanna piece of me?" Then the commercial desktops enter the fray, xig's CDE-like DeXtop rushing forward only to wedge in the pit of interoperability. Athene constantly regenerates but when the battle gets toe to toe, the obscurity spikes pin it down, the theme of the day turns Fvwm's way -- and it looks like we've a champion.

But what's this? The arena has been invaded. Who are these interlopers? screen has taken to the field, with twin nipping at its heels. A growl from behind, but they squish splitvt together, dtach another tiny opponent, then turn back to each other -- only to wail as emacs turns its Gnu-like head in their direction, establishing a sessions server...

Is it possible for there to be any more carnage than this? Probably. Seen on alt.sysadmin.recovery:

I am now taking bets on when this planet will reach its window manager event horizon. At some distant point in the future some sort of alien life-form is going to land on this planet and find everything dead except for a lone Sparcstation in an abandoned building waiting for a consignment of small lemon-soaked Motif widgets to be loaded.

-- Peter Gutmann

Ok, ok. That was overkill. I'm sorry, really sorry that I had to pub late this month, but as you can see now, my place is a shambles. But I did find something cool while finishing up... hooray! Someone in Ireland actually *CAUGHT* a spammer. Better yet, got them hauled away by the cops. (Alleged, hah. Caught with everything but a patsy present in person and teary-eyed.) Not even April fooling. Enjoy your month, folks. I know I will.

[NOTE]So that's it. Answers by Jim Dennis, Ben Okopnik, Thomas, Faber, many others among The Answer Gang... and you! If you've got some great Linux answers - send them to us. Ideally the answers explain why things work in a friendly manaer and with some enthusiasm, thus Making Linux Just A Little More Fun! Good short bits will probably go in Two Cent Tips, but truly juicy explanations, especially those that get the Gnag jumping in, could end up here. We don't promise that we'll publish everything, though. Also - you can be anonymous, either asking or answering - just tell us so, and Tux will eat the herring we wrote your name on. We swear.

(?) Compile on one, run on another machine

From Ferenc-Jan

Answered By: Thomas Adam

Hi there!

I've got a question that may be of interest to the linuxgazette community. Where does one go to find out more about cross compiling? (I'm not even sure cross compiling is the correct term for this.)

(!) [Thomas] Cross-compiling refers to compiling applications on a computer that is not intended for the same computer because often the target computer has a different architecture.

(?) The case is this: I often want to compile stuff on one machine but run it on another. My permanently-in-disrepair, bleedingly fast & incredibly messy test system is the machine of choice for compiling all kinds of linux stuff. The barely alive, old laptop or the lean & mean firewall box aren't - besides, I don't want a full blown gcc environment on those. But I run into problems most of the time.

Approach A: compile it as per instructions. Then I have to go and find all the nitty bitty parts of the package, that are now residing everywhere on the test system's drive. This often fails because missing parts don't always generate comprehensible error messages.

(!) [Thomas] This is not an approach, this is what usually happens when you compile a program.

(?) Approach B: try to install it to a different directory, i.e. /tmp/ and then move it to the other machine. This often founders on hard coded file location, i.e. when /tmp/lib/something is actually at /usr/local/lib/something (like it should be.)

(!) [Thomas] This is dependant upon how ldconfig registers where the libraries are (possibly by way of $LD_LIBRARY_PATH).

(?) I don't consider myself a beginner, but who does. I don't seem to be able to google the answer to this problem, but surely I'm not the only one running into this?

Any hints would be much appreciated, but I understand this must be relevant to linuxzgazette before you can spend your time on this.

(!) [Thomas] I'm not quite sure what it is you're asking. If it is "how can I compile applications such that I can minimise the number of (likely) errors", then the answer is to compile it statically so that the application doesn't have to go using any external libraries. Thr only disadvantage with this is that the resultant binary is often very large.
Dynamic libararies are the most popular -- much smaller, but it does mean that it is up to the user to ensure that these libraries are installed. 'ldd' goes a long way to checking and ensuring that is the case. But at compilation time, the user is often told what libraries (if any) are needed.
The querent then reported back that all was right with the world and that he found what he was after. I suppose we call all learn a lesson here in that being precise is important when asking questions, otherwise your question may never get the correct answer! -- Thomas Adam

(?) Anyway, another helpful soul came up with the answer on usenet: 

make prefix=/tmp/foo install.

That is exactly what I'm looking for. With this I can drop everything in an empty dir, gzip it, move it to another machine and unpack it & run it. Never thought it would be this simple, I tried this with configure --prefix=/tmp/foo, but that's where /tmp/foo gets into the compiled files.

(?) Dedicated Linux application

From Jon Aldrich

Answered By: Thomas Adam, Kapil Hari Paranjape, Jay R. Ashworth

I am in the process of developing a linux app (for gaming). I want the final product to reside on a linux box that, after booting, automatically runs the application. What is the preferred method for doing this?

1) An 'auto login' for a special user on one of the system consoles, who's user profile starts the application.

(!) [Thomas] You could add something like this to the user's ~/.bashrc 
[ "$(tac ~/.xsession | sed -n '2p')" = "the_name_of_my_game" ] && {
   startx &
}
(!) [Thomas] which says that if the penultimate line starts with your game program name then launch X, otherwise don't bother. Why the penultimate line? Because the last line in ~/.xsession should ALWAYS an "exec call" to your window manager. Of course, should you add anything to that file, the number passed to sed will have to be changed.

(?) 2) Start the app with an inittab entry.

(!) [Thomas] No. Doing this is deprecated and will cause all kinds of weird errors. What happens say, if X crashes? Each time X tries to start (based on the run-level X starts in) the game will also try to load, and so you get a feedback loop. In the case of Debian, X is started throughout runlevels 2-5.

(?) 3) Something else?

The app will produce graphics output and get user input, so it can't run as just a backgroud type daemon. It will run on a secure, dedicated network

Is there an info source or HOWTO for this sort of "bringing to market, implementation" kind of topic?

(!) [Thomas] I would just have it launched from within the user's ~/.xsession file (see above).
(!) [Kapil] One of the lesser known methods. An "@reboot" entry in the crontab. This will start a program just after "crond" is started.
(!) [Thomas] Not unless you have read: 'man 5 crontab', it isn't!!

(?) One other small question. Is it possible to display a flash screen of some sort during the boot sequence and pipe the boot data to the bit bucket? Sort of a "boot -quiet" option.

(!) [Kapil] I think there is a "bootsplash" patch to the kernel that does this.
(!) [Thomas] I think Jon was referring specifically to his game's flashscreen.
(!) [Jay] You'll get lots of opinions, I suspect, but mine is 'put it in inittab'. That and (optionally) an sshd should be about it: you should know everything that's running in a ps, in this kind of environment.
Make sure the bios boots the HD (/flash image) and nothing else, and is passworded. Yes, even if there isn't a hardware keyboard.

(?) Diagnosing a Linux crash

From Tom Brown

Answered By: Thomas Adam, Karl-Heinz Herrmann

OK guys, here's a n00b question for you that probably crosses over into Sys Admin territory.

What steps should someone follow after Linux crashes to figure out what went wrong?

Where do I start, and where do I look for clues?

Are all the logs found in /var/log, or are there others?

In what order should I look at the logs, and what should I look for?

(!) [Thomas] It depends what you think went wrong. Essentially: 
/var/log/messages
is where syslogd will dump all its data and so is the best place to look. But there may well be application specific data in /var/log (XFree86.0.log) is one such example.

(?) Any pro-active steps I should be taking to get more info, should it happen again?

The specifics of my case: my file server (a 750 Mhz Athlon running Suse 9) simply locked up, and I couldn't get anything to display (GUI or command line). I knew the machine was in trouble, when it didn't respond to pings. I had to hit the reset button to get it back (and deal with fsck, naturally). Funny thing is, the system clock reset itself to 28 minutes after midnight (when it should have read the middle of the afternoon), but didn't loose the date. Odd, that. The machine's been running 24/7 for about three weeks now (I set it up around then), and no sign of problems until now.

(!) [Thomas] This might be framebuffer related. At the lilo/grub prompt, type: 
linux video=vga16:off
(!) [Thomas] to see if that has any effect.
There have been snippets of these effects metioned in the past. The one that springs to mind is:
http://linuxgazette.net/issue74/tag/9.html
(!) [K.-H] There are ways of still getting kernel info (pro active steps):

(?) I'm going to keep your response handy -- several things to try. Meantime, I realized I was booting the thing into runlevel 5 (rather stupid, actually), so I've since changed it to 3. If it is, as someone suggested, a framebuffer problem, maybe that will solve it for now. I'm using a real old Voodoo 3 card I scrounged from my parts bin. If it happens again, I'll have to tear the machine apart and start playing with the memory, as someone else here suggested.

(?) install and configure Linux is one thing. Learning how to do an autopsy seems to be quite another!

(!) [Thomas] That's because generally one doesn't do it quite like that. Problem diagnosis is situation dependant. In any givem situation there is often a small set of files and related information that you can analyse without having to worry about the rest of the system.
Granted, this is related to how much information one is told at the time (if you've been on this list for as long as I have, you'll come to realise that usually we don't get any), and whether or not the person has tried to remedy it.
In general though, poking around, taking an aspect of your system, looking at what it does, and how is all related and helful to you when you have to come to diagnose anything.

(?) Yes, well, I looked at the messages log, but saw only a gap time-wise between cron processing around 4 in the morning, and the time of the crash. I'm not sure which of the other logs are important in that case. Where do I find the register dump (although I suspect it won't make much sense to me, rather like those register dumps you get in Windows XP)?

(!) [Thomas] Syslogd might have logged it, if the problem was software related, and indeed if the said program produced any errors. If hardware then it might not have, depending on the severity of the hardware failure.

(?) I'm using a real old Voodoo 3 card I scrounged from my parts bin. If it happens again, I'll have to tear the machine apart and start playing with the memory, as someone else here suggested.

(!) [Thomas] It might be memory, but as the link I have you last time around said, memory problems tend to be more 'visible' in the sense that you get a lot of applications SEGFAULTing and SEGABRTing for no apparant reason. In such instances, installing and running 'memtest86' is usually of help.
(!) [K.-H] Most of the time I had the great luck of oopes and kernel crashes occuring in the scsi layer, often hardware problems. If the scsi layer is in trouble nothing will get written to disk. What's software related regarding the kernel? The kernel deals with hardware, and it's supposed to handle error conditions gracefully, i.e. not just freeze without a hints whats gone wrong. But there are situations where the kernel doesn't have a chance of leaving hints on harddrive.
Then a few thing might be useful: (to Tom B)
suggested reading:
/usr/src/linux/Documentation/oops-tracing.txt
ksymoops man page
But I have to say that often enough I also do not try to hunt spurious crashes which do occasionally happen. Either hardware causes or whatever. You always can try a different kernel or simply hope for the best.
Still -- keeping the system on konsole 10 is not a difficult thing to do and it just might give you something useful next time (note it down for ksymoops if it's a oops or panic).
SuSE has memtest as bootoption -- run it if you suspect the RAM, run it long (several passes) and the full test suite if you don't find any errors on the first go.

(?) Thanks Karl and Thomas. This is the starting point I needed. (For one thing, I didn't even know about konsole10: looks helpful). I just wish I had more from the crash than just a black screen, but that's what I get for running X on bootup for a file server. Between the two of you, I think I have the answers I was looking for when I started this thread: not what went wrong exactly, but how to dig in, and try to figure it out for myself.

Oh, Thomas, when I rebooted to runlevel 3, I entered that video setting you suggested as well.

I just know I'll be back with more questions, though. One way or another, I'll figure this Linux thing out.

Thanks again, guys. Your help, as always, is much appreciated.

(?) I blew out Fedora with yum and 2.62

From Jack Sprat

Answered By: Benjamin A. Okopnik, Thomas Adam

I will try and balance brevity with information.

(!) [Thomas] Always a good thing :)

(?) I was on dial-up with kppp on an old 266MHz PC with Fedora running 2.6.2 kernel and running yum for the first time. I did not like the large number of not small files being downloaded to my machine and did a "kill -9" on the process. Bad bad bad. "ls" produced "Segmentation fault" as did several other commands. Machine would not reboot. Booted from rescue CDROM and "chroot" gave Segmentation fault".

(!) [Thomas] This is indicative that glibc had yet to upgrade. You should never hault the system in an upgrade if you can help it. Debian does a good job of recovery, but the point is that if you do, you'll have damaged and incomplete packages which will invariably break your system. Then you have to go down the route of rescue CDs and the like.

(?) Read up on chroot and created a static linked bash on a second machine and was able to chroot once this was in place. "ls" failed as did "vi"; pwd worked. On a good machine I compiled a static linked "ls"

(!) [Ben] *Ouch.* 
ben@Fenrir:~$ ldd `which ls`
                librt.so.1 => /lib/tls/librt.so.1 (0x4002a000)
        libacl.so.1 => /lib/libacl.so.1 (0x40030000)
        libc.so.6 => /lib/tls/libc.so.6 (0x40038000)
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0x40171000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
        libattr.so.1 => /lib/libattr.so.1 (0x40180000)

When any one of those libs isn't happy, ain't *nobody* happy; almost
all of them are critical core libraries from the "libc6" kit.
(!) [Thomas] pwd worked because you were using the bash builtin as opposed to the ELF version.

(?) (I had to add -static to linker and it complained about one function not being linked in, but seems to work. Should not one be able to make static linked copies of utilities/programs such as are in Fedora coreutils?).

(!) [Thomas] No, the whole point of having dynamically linked files is that their size is reduced, making them easy to put onto floppy diskettes, etc. Not only that it allows for greater portability.

(?) With "ls" in place on the damaged machine, I was able to see what I was doing and recovered /lib from a two week old backup after "chroot"ing to the damaged file system. I have cowardly retreated to Fedora kernels and the system boots and I have discovered no problems with one exception.

(!) [Thomas] Usually something like: 
mount /dev/abc /mnt && chroot /mnt /bin/bash
where /dev/abc is your damaged partition, is sufficient.

(?) On my good machine the route table when on dial up had a route to the server I am hooked up to and the name is resolved. On my damaged machine "host" and "dig" work in resolving names or IPs but the server name is not resolved in the route table. The real problem is neither Konqueror non Mozilla will go to any Internet site regardless of whether IPs or names are used. If an IP is used, such as 000.00.00.0 the name is resolved in the error message stating that "www.aaaaaaa.aaaaa.com not resolved.". Text browser lynx does work, although I am worse than a

(!) [Thomas] Sounds like you're missing: 
/etc/resolv.conf
and valid entries in there.
Hint: man resolv.conf

(?) newbie with it. I have checked network files in /etc and its subdirectories and compared to my good machine until I am blue. I have turned off the firewall and commented out hosts.<deny allow>. I have done "rpm -V" on all installed rpms. Although the listing is not perfectly clean, neither is it on my good machine. I suspect something in the /usr/lib directory. I do not believe I have been hacked but of course who knows? How would you proceed?

(!) [Thomas] This is not a /usr/lib issue, but more a question of configuration. As well as checking for /etc/resolv.conf, ensure that in the file: 
/etc/nsswitch.conf
you have the line: 
hosts:          files dns
That, is, make sure that dns is listed after files, as above.
(!) [Ben] I'm amazed at your persistence and quite tickled by yet another demonstration of how tough Linux is. In my experience and in the stories that I've heard from others, Linux systems can be rescued from all sorts of incredible damage - and you've (mostly) managed to pull it off.
I would back up all my data, clear out the partition, do a fresh install, and put the data back on. Yeah, you could be macho about it and try to trace everything down by function... which would leave you open to problems with subsystems you're currently not using (this will, of course, happen long after you've forgotten that this damage even occured.) Since you don't know exactly what you broke, you'll never know everything you need to fix; this is one of the situations where I'd apply my mechanic friend Ken's dictum of "keep removing stuff until you get to something you know is good and build up from there." It's also the most efficient approach at this point, IMO.

(?) I hate to clog your mailbox, but I wanted to thank Ben O. and Thomas A. for their rapid response to my 2/20 question and their insights.

I have decided to restore my backups (only two weeks old) and if that fails, reinstall from scratch and reload my data.

(?) 2c tip: filtering in-place

From Kapil Hari Paranjape

Answered By: Kapil Hari Paranjape, Ben A. Okopnik, Thomas Adam, Jay R. Ashworth

Hello,

I have always thought that filtering files "in-place" was not possible from the command line... ...until today---one lives and learns. 

  dd if=file bs=4k | filter | dd of=file bs=4k conv=notrunc

Where "file" is the file you want to filter and "filter" is the filtering program you want to apply.

Examples:

http://www.itworld.com/nl/unix_sys_adm/09252002

have a perl solution.

(!) [Thomas] Perl/sed/ruby all honour the '-i' flag, which is a started, then just apply regexps to match anything but the filter expression.
(!) [Ben] The "buffer" program does exactly the same as the above; the process is called "reblocking". 
buffer < foo | filter > foo
(!) [Ben] If the file is bigger than 1MB, you'll need to specify a larger queue with the "-m" option, but that's usually not an issue.
Conversely, as Thomas mentioned, you could use Perl's, etc. "in-place edit" switch: 
# rot13
perl -i -wpe'y/a-zA-Z/n-za-mN-ZA-M/' file

# lc everything
perl -i -wpe'$_=lc' file
(!) [Ben] buffer < foo | filter > foo
(!) [Jay] Oh, cause buffer reads the entire file before the '>' can stomp it?
Well, that's not exactly the same... :-)
Doesn't that still depend on order of evaluation by the shell? Is that defined?
(!) [Thomas] Well, yes....
  1. buffer < foo
  2. | filer is acted upon
  3. Resultant output to file
(!) [Jay] Well, not necessarily.
(!) [Ben] Well, yeah - just about as definitively as anything in Bash is. Otherwise Kapil's method wouldn't work either. Neither would piping anything through "sort". The left side of the pipe has to terminate before the right side can do anything with the output; in many cases, there is no output until just before the left side terminates.
(!) [Jay] In fact I think that's wrong: I don't think the dd method does depend on order of eval; the writing copy of dd can't try to write a block until it has it, so I believe that that method is guaranteed never to stomp data.
(!) [Jay] A shell could (un)reasonably decide to evaluate the output redirection (ie: stomp on the file) before the buffer program can read it. At best, it might be a race condition between the two sides of the pipe.
I don't think, intuitively, that it's at all reliable, where as I think the dd approach probably is.
(!) [Ben] Uh, not any shell that contains a working implementation of IPC. One that's broken, certainly. Chances are that if time ran backwards, it probably wouldn't work too well either...
Please state the mean and the average probabilities and the relevant confidence levels for the accuracy of your intuitive approach. The data generated in the course of your study may or may not be used as grounds for questioning during your exam. :)
(!) [Jay] Every shell programing I've read in 20 years warns againts that construct, precisely because most shells will set up the redirect first and stomp the output file. As for the pipeline, I believe that most shells exec the last component first. Maybe bash has changed that; I remember a warning about it in the Bourne book.
The nature of the thread changes slightly -- Thomas Adam
(!) [Kapil]
Hi,
Just a few additional remarks:
(a) perl, python and vi/ex do offer alternate solutions ... but see below.
(b) I couldn't locate "buffer"---where do I find it?
(!) [Thomas] Oddly enough, under Debian it is in the 'buffer' package.
(!) [Kapil] (c) Just to defend the "dd" solution a bit:
When the "dd" command-line given in the earlier mail is terminated (for any reason like a Control-C), it outputs the number of blocks read/written. Thus, the intrepid user can restart the process by modifying it with suitable "seek" and "skip" commands. Of course, this assumes that the filter operates on data sizes less than 4k independently.
(!) [Thomas] See the "-S", "-s", and "-z" to buffer(1) :)
(!) [Kapil] I became aware of this "dd" procedure while trying to (yes I'm crazy) encrypt one entire disk partition in-place. The problem with the other solutions is that they require a lot of memory to run.
As far reading and writing to pipes is concerned, here is how I understand it---please correct me if I am wrong. The kernel has its own internal settings on how much data is buffered before a writing process is put at the back of the queue and the reading process is woken up. Thus killing any one process in the "dd" pipeline could only result in less data being written than was read---an error from which one can recover as described above.
(!) [Ben] Since the source and the target file are the same, wouldn't you end up with some truncated version of your data (i.e., the source being gone no matter what)? It seems to me that the difference between complete destruction of data and truncation of it at some random point can only matter theoretically, except in a vanishingly small number of situations.
(!) [Jay] No, you wouldn't.
The target side dd is doing random access.
It writes the blocks sequentially, but it writes them into the standing file, one at a time, without touching the blocks around them. Likewise on the read side. The killer is the redirection, which his approach does not use, at all. Not the pipe.
(!) [Ben] Ah. I hadn't realized that. In that case, I agree; there's a large difference. I've just tried it on a 100MB file I've made up for the purpose, and it seems that you're right.

(?) framebuffer colors

From frank.n. dale

Answered By: Thomas Adam

Hello Gang,

Assume X is not running and your framebuffer allows for 256 colors or more.

Please give manual instructions (or C code) to write on the screen 64 characters in different colors.

(!) [Thomas] Hi, there. Assume for a moment that we cared. Then realise that actually this is The Answer Gang to do with Linux questions. Then assume that we do not answer homework questions. Then assume that you want to look here:
http://linuxgazette.net/tag/ask-the-gang.html
If you assume all of these, then you have a tautology.
Of course your programming homework is quite easy to do, it just requires that you do a little research first, as with any academic course you might be studying. It takes work, and if you are not prepared to put any in, why bother with it? If you do not understand it, then that is a different matter, to be taken up with your lecturer.

(?) Please do not forward this query to Thomas Adam, he does not know.

(!) [Thomas] Unfortunately, I do.

(?) How do you set and get colors outside the range 0-F hex when using framebuffer in the Linux console?

(!) [Thomas] For this, you will have to look at vga.c in the kernel source, and at fb.c. You will almost certainly have to hack the kernel source to allow this.

(?) This query is not a home work exercise. It is based on fruitless Goggle search of many hours over a span of several months. The major framebuffer sites

http://linuxconsole.sourceforge.net/fbdev http://linux-fbdev.sourceforge.net http://www.directfb.org

do not deal with it nor does the HOWTO-framebuffer. Also the console escape sequences for colors only apply to colors 0-F.

The only solution found so far involves the SVGALib which is too much of an overhead. There must be a simpler solution. Do you know more than I do?

(!) [Thomas] SVGALib is nothing to do with framebuffers, but it will allow you to display console screen resolutions higher than the default.
(!) [Heather] Other than the vague bit about it being able to use FBDev as its video type, if you have a framebuffer enabled kernel and your monitor settings are right in /etc/libvga.config.

(?) The query is relevant for syntax coloring in the Linux console (text, no X). With the standard 16 foreground and 8 background colors, syntax coloring is a pain in the eyes. With the 256 colors or more that you get from framebuffer, syntax coloring could become pleasant and effective.

(!) [Thomas] So why not run your console with a setting of: 
vga=0x317
while will run a 1024x786x256 colours.
Look here: 
Colours   640x400 640x480 800x600 1024x768 1152x864 1280x1024 1600x1200
--------+--------------------------------------------------------------
 4 bits |    ?       ?     0x302      ?        ?        ?         ?
 8 bits |  0x300   0x301   0x303    0x305    0x161    0x307     0x31C
15 bits |    ?     0x310   0x313    0x316    0x162    0x319     0x31D
16 bits |    ?     0x311   0x314    0x317    0x163    0x31A     0x31E
24 bits |    ?     0x312   0x315    0x318      ?      0x31B     0x31F
32 bits |    ?       ?       ?        ?      0x164      ?
(this is for: vga=<foo> in /etc/lilo.conf).

(?) Mirror 2 web servers

From Bradley Chapman, Thomas Adam, John Karns, Ben Okopnik

Hi folks at ,The Answer Gang

I have two webservers running linux (redhat) one of them is the primary server and the other one acts as backup

the thing is that i want to be able to mirror these servers in both ways

including this:

(!) [Bradley] Well, since you're using a MySQL database, have you considered moving the MySQL database and DBMS onto a third machine which is more powerful than the two webservers, and simply having the webservers query the database using your favorite RDBMS protocol. Or you could use the MySQL mirroring and load balancing features (Google turns up a lot of links).
Many online websites, such as discussion forums, often place the DB onto a separate machine and the Web server software onto another one (or two, or any value of N), and use DNS round robin to rotate amongst the Web servers, thus lessening the risk that a single machine failure will kill the site.

(?) i was thinking a shell script would do the trick! but my competence ends just after #!/bin/bash!

i am not asking for a complete script

just some were to turn for help :)

(!) [Bradley] You can help us by supplying ASCII art defining your network topology - the really smart people who know DBs and stuff on this list will probably need it ;-)
(!) [Thomas] Have a look at the 'rsync' utility -- that will fit your needs quite happily.
(!) [John] Just thought I'd mention a few general suggestions.
To read up on bash scripting, you might want to take a look at the "advanced bash scripting guide" at one of the following URL's.

...............

Linux Documentation Project: http://www.tldp.org/LDP/abs/html http://www.tldp.org/LDP/abs/html/index.html http://www.tldp.org/LDP/abs/abs-guide.html.tar.gz http://www.tldp.org/LDP/abs/abs-guide.pdf
Sunsite:
http://www.ibiblio.org/pub/Linux/docs/linux-doc-project/abs-guide
Postscript --
http://www.ibiblio.org/pub/Linux/docs/linux-doc-project/abs-guide/abs-guide.ps.gz
Text --
http://www.ibiblio.org/pub/Linux/docs/linux-doc-project/abs-guide/abs-guide.txt.gz
Sunsite:
http://www.ibiblio.org/pub/Linux/docs/linux-doc-project/abs-guide
Author's home page: http://personal.riverusers.com/~thegrendel/abs-guide-2.6.tar.bz2 [ 624k ] (bzip2-ed tarball containing SGML source, all example scripts, and rendered HTML)

...............

"man bash" at the command prompt will yield the extensive bash man page, assuming that you have it available on your system.
Also, there are some articles on the subject in the archives of the Linux Gazette, some of which were authored by Ben Okopnik, one of the members of the answer gang.
(!) [Ben] Yep. Just search for "shell scripting" (including the double-quotes) at <http://linuxgazette.net/search.html>; and you'll see it right at the top of the stack.
(!) [John] The rsync utility is often used for mirroring and can save bandwidth. For the MySQL side of it, you may need to get a bit more creative. I would suggest fishing around on the 'net for DB mirroring with MySQL, as I think rsync is intended more as a tool to deal with plain ASCII files, although I could be off on that.
(!) [Ben] [grin] Just a little, John. "rsync" is intended for file transfer in general, no restriction as to type. I use it with the "-e ssh" option (actually, I have "RSYNC_RSH=/usr/bin/ssh" set in my "~/.bash_profile"), so it uses SSH as the underlying mechanism, but "rsh", although deprecated in most situations, is also type-independent (although it's somewhat clunky - the STDIN/STDOUT method of transferring data does make it look like a text-specific gadget.)

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Published in issue 101 of Linux Gazette April 2004
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Published in Issue 101 of Linux Gazette, April 2004


News Bytes

By Michael Conry

News Bytes

Contents:

Selected and formatted by Michael Conry

Submitters, send your News Bytes items in PLAIN TEXT format. Other formats may be rejected without reading. You have been warned! A one- or two-paragraph summary plus URL gets you a better announcement than an entire press release. Submit items to bytes@linuxgazette.net

Legislation and More Legislation

EU IP Enforcement

The EFF has reported on a recent vote in the European Parliament, adopting the Directive on Intellectual Property Enforcement. This gives rights holders new tools with which to attack intellectual property infringers. The proposals make little distinction between unintentional, non-commercial infringement by consumers, as opposed to the for-profit quasi-industrial infringement practised by professional pirates.

European Microsoft Case

As reported by The Register The European Commission has found that Microsoft has abused its position as a monopoly in the market. The findings centered on Microsoft's use of its dominant position in the OS sector to acquire market share in associated products (e.g. media player).

The remedies imposed include requiring the disclosure of interface documentation to allow non-Microsoft work group servers to inter-operate with Windows systems. This information must be updated as products change, and Microsoft will be entitled to remuneration "To the extent that any of this interface information might be protected by intellectual property in the European Economic Area". Microsoft will also have to offer to PC manufacturers a version of Windows without Windows Media Player. A fine was also imposed.

Though some, such as Sun Microsystems, have strongly welcomed the ruling, others are more sceptical about its potential to change matters. Indeed, the licensing of APIs may offer a welcome new revenue stream to the Redmond company.

Linux Links

Concerns about European patents

LinuxDevices.com's Embedded Linux Market Survey

How Not To sell Linux Products

LXer (pronounced Elexer) is a newish (January) Linux news site. Well worth a look.

Simputer uses Linux

Linux in the living room

8 rules for open-source business strategy

Video production with Linux

creating PDF files with ps2pdf

A look at the state of Linux on PS2

Linux 2.6 at illuminata

Macromedia to offer Linux support on a trial basis

Hiring Open Source Developers

Linux Warcry asks what are the alternatives to XFree86 while The Age has a useful report on the licence issues between Apache, XFree86 and FSF

Wireless Linux

CEOs say Open Source keeps IT spending down and and saves money

Comic-book publisher turned IT-company aims to bring Linux and new hardware platforms to China at large

Ian Murdock on the future shape of Linux distributions

Linux distributions around the world

Hyper-threading and Linux

SCO goes quiet in Germany following an out of court settlement with Univention. Effectively, they seem to be prevented from publicly expressing most of the statements behind their case.

Copyright law stifling art with DJ Danger Mouse's Grey Album

Networking improvements in the 2.6 Kernel

Introduction to the Gumstix, a tiny Linux computer

Creating UNIX screen-capture movies

Migrating to 2.6

Cold war between open and closed source camps

Comparison of Linux 2.6.4 vs 2.4.25 while NewsForge asks is the 2.6 kernel ready for general distribution?

News in General

GNOME

The GNOME Project had the misfortune to experience an intrusion on the server hosting www.gnome.org and some related gnome.org websites. However, it is unlikely that sources were tampered with, and by all accounts this was a minor intrusion.

Apache

The Apache Software Foundation, and The Apache HTTP Server Project have announced the release of version 2.0.49 of the Apache HTTP Server. As well as fixing three security vulnerabilities, this new release also includes numerous enhancements and new features.

OpenOffice.org

OpenOffice.org has released a new version of the popular office productivity suite: OpenOffice.org 1.1.1. This is primarily a bug-fix release though it does include a few new features as well.

The Gimp

The Free image manipulation and graphics tool the Gimp has reached version 2.0. This is a major release, and marks the advent of official support for the software on MS Windows and Mac OS X, as well as the traditional Unix-based operating systems. As well as the official press release you may be interested to read the descriptions of the new features included in this release. The software can be downloaded now from various mirror sites.

Distro News

Debian

Debian votes to keep non-free.

The Debian package Popularity Contest aims to help order the applications that will be included on the estimated 13 binary CDs sarge will ship on when released. Participation is simply a matter of installing the popularity contest package.

Gentoo

The O'Reilly Linux devcenter has published an account by Danny O'Brien of a talk given by Daniel Robbins, Gentoo's chief architect. Also of interest is the review of Gentoo at LXer.

Mandrake

Mandrake has relisted on the stock market after filing a plan for the repayment over the next nine years of its outstanding debts.

Mandrake has also released a new revision of their operating system Mandrake 10.0 Community, which features the new 2.6 kernel.

UserLinux

Bruce Perens on UserLinux

Software and Product News

GFI

GFI has announced that it is developing a Linux version of its GFI MailSecurity product, and that it will be adding support for Linux-oriented features in all its products. Previously, GFI MailSecurity was available for Microsoft Windows.

Linux Pocket Guide

O'Reilly has launched a new Linux reference book. The new "Linux Pocket Guide" by Daniel Barrett aims to be a useful reference for new and experienced Linux users who need a quick and handy means to look up Linux commands.

Mick is LG's News Bytes Editor.

[Picture] Born some time ago in Ireland, Michael is currently working on a PhD thesis in the Department of Mechanical Engineering, University College Dublin. The topic of this work is the use of Lamb waves in nondestructive testing. GNU/Linux has been very useful in this work, and Michael has a strong interest in applying free software solutions to other problems in engineering. When his thesis is completed, Michael plans to take a long walk.

Copyright © 2004, Michael Conry. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Leaning Out of Windows

By Tom Brown

This is a follow-up to my earlier article, "I Don't Think We're in Redmond Anymore, Toto" (Issue #97, December 2003), in which I described my introduction to, and first impressions of, Linux. In this article, I wanted to give you my further impressions and experiences, so you have some idea what it's been like to go full-time (more or less) from Windows to Linux. In the process, I hope to pass on some helpful tips. Hopefully, you who follow in my footsteps can avoid stepping in some of the doggy-doo that I faced (faced? now there's a mental picture I could have done without).

Choosing a Linux Distro

The first thing you need to do after deciding to give Linux a try is choose a distro. There are a lot of them out there, with different features and benefits to each one. I myself started out with Mandrake, and was happy with it until I raised my computer's memory to 1GB, at which point the default version of Mandrake refused to run. Unwilling to play around with it, I changed over to Red Hat 8 (and subsequently upgraded to Red Hat 9). My main reason for choosing Red Hat was the large number of companies that used it. In time, I'd like to make a living using Linux, so it seemed like a natural choice. In my opinion, RHL9 wasn't as easy to use as Mandrake, but it worked well enough.

One day, I received the "end of life" email from Red Hat, which gave me the choice of upgrading to their Enterprise version, Red Hat Enterprise Linux, or switching to the "hobbyist" version, Fedora Core (I refuse to call it "Fedora", since that name has been in use since 1998 by Cornell University and the University of Virginia for a different project). Suddenly, I was back to choosing a Linux distro again. The one choice from Red Hat was too expensive, and the other looked like a permanent beta version to me (sorry guys, I know some of you disagree). I decided to look at other distros, and finally settled on SuSE 9 Professional.

In the course of this article, I'll mention some of the features in SuSE that attracted me to it, and which have made my life easier. Everyone has their favorite distro, of course, so before you jump into the Linux universe, talk to others about which distro they're using and why. Even if you're just playing around with Linux, you'll be a lot happier if you do your homework first.

Installation

Most Linux distributions are simple and straightforward to install (some don't even need installing, but run right from the CD). As long as the distro's new enough to recognize your equipment (or your equipment is old enough), installation's a snap.

At this point in your exploration of Linux, your biggest problem is going to be hardware support. I already mentioned that Mandrake didn't support my 1GB of memory. Neither Mandrake nor Red Hat recognized my Promise Raid controller (Red Hat saw it as two separate disk drives, and wanted to "fix" them for me). Red Hat also had problems using my LCD monitor. You may have to make some decisions here: do you want to stick with the distro you selected, or do you want to use that one piece of hardware? Someone that knows a good bit about Linux can probably fix what's wrong, but if that someone isn't you, you'll have to choose. When I discovered that SuSE supported all my hardware, my choice was made.

Getting It Just Right

For many, once Linux is installed, that's the end of it. Time now to start playing with it. But what if you need to change something? Perhaps you want to share a directory with a Windows machine on your local network, change the settings of the firewall, or use that 15-year-old laser printer that's sitting in the attic collecting dust.

These tasks, and others, aren't as simple as you might think from your experience with Windows, but they're not impossible, either. Different distros may have their own custom tools to make these jobs easier, but many times, it comes down to manually editing a configuration text file.

There are a lot of good text editors to help you here. Some are character-mode DOS-like applications(e.g., vim, emacs, joe, jstar), while others are Windows-like GUI apps (e.g., kvim, xemacs, Kwrite, Kate, Gedit), so use the one you're most comfortable with. In any case, you'll find the configuration files off the root directory under /etc. Now, you're going to need help understanding these files, which means searching the web for "HOWTO" docs for the job you're trying to do (e.g., "Samba-HOWTO-Collection.pdf").

[ Some distributions have a collection of HOWTOs available as an installable package, or you can simply search the Net for "<keyword> HOWTO". - Editor ]

This is one of the places where SuSE attracted my attention. SuSE has a tool called "Yast2" (for "Yet Another Setup Tool"), which eliminates most of the work configuring both hardware and services. Most Yast screens have a separately-scrolling help panel on the left side, describing the fields to be configured on the right side panel. This help usually supplies you with enough information about the fields to make the correct entries. Each of the system changes I mentioned above (Windows share, firewall, printer setup) are a snap using Yast2. When you click the "Finish" button, Yast2 does whatever is necessary to make your change effective, including restarting services (otherwise, you'd have to go to the command line, and do it yourself). Someone comfortable with Linux, the command line, and the /etc directory, would want to do most of this manually. For someone from the Windows universe, however, a tool such as Yast2 makes Linux a lot less intimidating. This doesn't completely eliminate editing /etc files, but it handles most jobs.

Other distros have their own methods of making configuring your system easier. Red Hat, for example, uses a lot of little programs, instead of the one monolithic one used by SuSE. As I said above, ask people what distro they use, and how this sort of feature works there. I can only tell you from my own experience. I like Yast2, and it (along with the distro's default use of KDE instead of Gnome) are what sold me on it. YMMV.

Disaster Recovery

Even the experts make mistakes. Those of us still near the beginning of the Linux learning curve make a lot of them, so prepare for the worst. Once you have your system set just the way you want it, perform a backup of two things: the /etc directory (that's where all your carefully-crafted system settings are stored), and the contents of your home directory. One important tip here (from personal experience): if you're using drag-and-drop to copy the files somewhere, make sure you tell the file manager to show hidden files (in KDE, it's under the View menu) first. Files that begin with a period are hidden from the GUI file manager by default, and that's where your personal settings are stored. If they're not visible, they're not going to get copied. You've been warned.

Another note on the SuSE 9 distro. The install CD (and the DVD) has a GUI-based system repair tool. One of the things it will repair is the boot process (e.g., if a Windows re-install overwrites the Grub boot sector), but it checks for, and fixes, a load of potential problems as well. It's saved me on more than one occasion.

My Security Rant

OK, I'm gonna get on my soap box with this one. There has been a lot of talk in the press about viruses, trojans, and worms (oh, my!) attacking Windows. A lot of you may be thinking about moving to Linux to avoid all of that. Some say that the reason Windows gets attacked and Linux doesn't is that Windows has a lot more users.

As Sherman Potter of the 4077th would say, "Horse hockey"! Windows, IMHO, is inherently insecure, mainly due to design decisions that go to the heart of the operating system. This cannot be corrected without fundamental changes to Windows, which no doubt would break nearly all existing applications. Applications and system services are integrated to operate together on a very low level. In many cases, they have to be in order to work. Notice the recent Microsoft announcement that XP Service Pack 2 will break some applications because of its security enhancements. When a flaw surfaces in one Windows application or service, it can seriously impact the entire system. This is like having repeated unprotected group sex with complete strangers (I think that's another mental image I didn't need). This goes beyond the question of allowing Outlook to execute code inside an email. The modular structure of Linux discourages this sort of behavior, helping to keep programs from interacting in ways they shouldn't.

If you want to secure your Linux installation against attack, I have a few suggestions. Home users don't need to run an antivirus in Linux if they follow a few precautions. First, don't run a web or ftp server that's visible outside your private network. Second, keep your computer behind a router (which is also the easiest way to share a cable or DSL modem between two machines). Third, if you're connecting to the Internet via WI-FI, enable the strongest protection you have (WEP, WPA, etc.), and make sure your Access Point will only connect with the MAC addresses of your own machines, so strangers can't come in. Fourth, don't run any script or program from a source you can't trust. Note that Windows programs won't run in Linux (unless you run them in Wine), so they're not a problem. Finally, don't poke unnecessary holes in your firewall. It's like leaving the windows open (if you'll excuse the expression) in a parked car. If you don't see a problem leaving your car windows open all night, then it's obvious you've never been to my old neighborhood.

Installing More Programs

At some point, you'll want to install programs that didn't come with your Linux distro. After hardware configuration, this is the most difficult part of Linux to adjust to for the Windows user. Some distributions, such as Mandrake, Red Hat, and SuSE, use "RPM packages", a format originally designed by Red Hat. Many of these packages can be used on any Linux that accepts RPM files, but there are a few that may be specific to one distro or another. Many packages that can be used in any Linux are marked as specific to Red Hat, so you may have to look around, or ask someone, to find out if it will work with your distro. You could just try it, of course, if you're feeling lucky (for a moment there, I thought I heard Clint Eastwood). These packages are installed using the command line, and a program called "rpm". A good tip for using the "rpm" command (which I mentioned before) is to always use the "-v", or verbose option. This will give you a better idea what went wrong.

RPM packages can suffer from a dependency problem. For example, if a package needs version 2.3 of a particular library to work, and you only have 2.0 on your machine, that's a dependency problem. This hasn't happened to me lately, but I've been keeping my system up-to-date (Yast2 can automatically check for, and apply, updates), so perhaps that's the key to success.

While I've never worked with it, I understand that Debian has something called "Advanced Package Tool", or APT, that solves the dependency issue. But, as I said, I've never used Debian, so can't tell you how well APT works. People I've talked to swear by it, however, and would never use anything else.

It doesn't solve dependencies, but the Yast2 tool in SuSE automatically opens when you double-click the icon of an RPM package. The tool allows you to see a description of the package, and a list of the files in it (including the complete file path of each). You install the package with the click of a button. Yast2 isn't perfect. I've experienced problems with installing a few packages, and was forced to use the "rpm" command from a shell, but this didn't happen very often. All in all, SuSE makes installing RPM programs a lot easier than using "rpm" by itself.

Another method you'll see for installing programs is the use of a shell script (usually with the file extension ".run"). The ones I've looked at have what appears to be random characters at the end. This is normal, and constitutes the material to be installed. You just run the script to install the program. As with all shell scripts, if you can't run it, check its permissions (in KDE, you'll find it in the Permissions tab of the icon's Properties dialog) to see if the file can be executed. Unlike Windows, Linux won't run any script or program file that doesn't have the "execute" bit set.

Finally, we have an installation method that is both better and worse than the others. You download a "tarball" containing source code, then compile and install it. A tarball is a archive file, usually compressed with "gzip", with the extension ".tar.gz" (or sometimes just ".tgz"), which you have to unpack into a directory before you can do anything with it. From a command line, you can type the following to do so: 

tom@MYMACHINE:~/temp> tar xvzf programname.tar.gz

If you're using KDE's file manager, there's another way: right-click on the tarball's icon, and select "extract here", "extract" or "extract to". The first menu option uses the program "Ark", while the other two use the program "Karchiver". If your familiar with using a flavor of "zip" on Windows, you know that not everyone creates an archive so that the contents extract into their own directory. This can make as much of a mess in Linux as it does in Windows, so always unpack the tarball in an empty directory, where it won't make a mess.

Once you've unpacked the tarball, you're ready to compile and install. Don't be scared of this, even if you've never done any programming. All you have to do is type three separate commands into a shell: 

tom@MYMACHINE:~/temp/expanded_tarball_dir> ./configure
tom@MYMACHINE:~/temp/expanded_tarball_dir> make
tom@MYMACHINE:~/temp/expanded_tarball_dir> make install

When this works, which is most of the time, it's great. I've occasionally had trouble with it, however. Sometimes, it's a matter of running some (or all) of the commands as root. Sometimes, the tarball is missing a file. Other times, it fails because it can't find the source it needs from elsewhere in your system. The benefit of this installation method is that the resulting binaries are built specifically for your system. You do, however, need to have the proper compilers installed.

If you run into any problems, or see error messages you don't understand, just step back, take a deep breath, and check out Ben Okopnik's excellent Linux Gazette article "Installing Software From Source", from Issue #74. It goes into a lot more detail about this, and is a good starting point for tracking down your problem and fixing it.

Running Windows Programs in Linux

You can run some windows programs in Linux. Not all of them, but a few of the key ones can be used if you know how. "How" is through a program called Wine (which stands for "Wine Is Not an Emulator"). The best way to use Wine is to make a copy of a real Windows directory (I use an old installation of Windows 98), and have Wine use it as part of a "fake c drive". You install programs into this fake drive by inserting the appropriate installation CD (for example, a Microsoft Office CD), and entering a shell command such as: 

tom@MYMACHINE:~> wine /media/cdrom/setup.exe

You'll see the familiar Windows installation screens. Not every program will work, however. For example, I haven't gotten Visio 2000 (the one from Visio Corp, not Microsoft) to install yet. Once a program is installed, you run it using a shell command such as the following. 

tom@MYMACHINE:~> wine "/c/Program Files/Microsoft Office/Office/winword.exe"

I believe the most compatible version of Microsoft Office is 97. Later versions may not work completely. Where possible, though, you should avoid using Windows programs in Linux, since many programs work best when working with their native operating system. There are a lot of open source Linux programs out there, and you should check them out before falling back on a Windows app. Besides, your goal is to migrate away from Windows, right?

The Open Office Word Processor

OK, I confess! The only part of Microsoft Office I really use is Word. I've mostly had good luck using the Open Office word processor, but I've had a few problems when loading a Word document, editing it, then saving changes out to the same file. Most of those problems dealt with tables, and resulted in a scrambled page when viewed in Word. The same page would look just fine in Open Office.

My advice when editing word documents is to double-check the document's appearance in Word itself if the document has complex formatting (i.e., is not a straight-forward bit of text). The version of Open Office I used was 1.1, and this sort of problem may be corrected in newer versions. I fixed the document mentioned above by re-creating the table format from scratch in Open Office, then copying the text from the original document.

Similar to using Wine, I recommend sticking with the native format in Open Office, and only save the document in Word format when you're ready to give it to someone.

Games

I still end up playing video games in Windows, rather than Linux. Mostly, it's because there aren't a lot of new games released for Linux. And, while some older games will work under Wine (e.g., Jedi Knight Outcast), not all of them will. A common problem I've seen is that a game will install under Wine, but when you go to run it, it complains that you're running a debugger. It tells you to exit the debugger and try again. This is a copy protection mechanism, and I don't know if there's a work-around for it.

Another problem I've seen in Wine is with games that come on two CD's. Midway through the install, it tells you to change disks. Sometimes you can, and sometimes you can't.

Then you get a game such as Unreal Tournament 2004. It's available natively for Linux (no Wine needed), and runs beautifully. Besides being a fabulous game, it looks great under Linux, and runs fast, even with all the eye candy turned on (I have an nVidia Gforce 4 card with the nVidia 3D driver). Disclaimer: to date, I've only been able to play the demo.

Some manufacturers give you a Linux engine for their games, but you have to supply the rest of it yourself (e.g., levels). An example of this is Serious Sam First and Second Encounters. You download an installer for free, which asks you to insert the original game CD. While both of these particular games work OK, they don't recognize all of the mouse buttons (Logitech's two thumb buttons in particular). In contrast, Return to Castle Wolfenstein works perfectly, mouse buttons and all. If you already have the Windows version of one of these types of games, download the Linux installer and try it.

Don't ignore the games that come free with Linux, however. My favorites are Frozen-Bubble (simple, and very addictive) and Armagetron (a 3D version of the Light Cycles in the movie Tron).

Ripping and Burning CD's

So you just bought a new audio CD, and want to convert the songs on it to MP3 or Ogg Vorbis format then burn a CD for use in your portable player. This can get complicated for the Windows user. In Linux, you're often dealing with a lot of separate programs for this, instead of a do-it-all program like MusicMatch or iTunes. Some of these programs are actually command-line driven, with a separate program to serve as a GUI shell.

You're going to need a program to convert from the audio CD's ".wav" format to MP3 or Ogg. When dealing with MP3, the most common conversion program is called "Lame" (there are others). Once you have a copy of Lame (or whatever), you just plug it into the program you're using to "rip" the CD (e.g., "Grip").

You can use the command line programs alone for burning CD's, but you don't have to. There are several GUI alternatives out there, such as K3B and cdbakeoven (I lean more towards cdbakeoven). I haven't tried burning a DVD in Linux yet, so I can't tell you whether, and how well, these two programs work for DVDs.

Network Sharing

One of the things I wanted to do was take an old 750 MHZ computer, and turn it into a file server for both Linux and Windows clients. Yast2 made quick work of setting up both Samba (Windows sharing) and NFS (native Linux/Unix sharing). If you're not using SuSE, you can use the Samba browser tool, or just write both configuration files (Samba and NFS) by hand with a text editor. Find and read the HOWTO documents, and follow the examples. I had only one problem with my installation: I was using my router for DHCP (in which each computer in the network gets its IP address from the router), but couldn't fetch the IP address of the other network computers from the router. I ended up giving each computer a fixed IP address. Not pretty, but it works.

Getting Rid of Internet Ads

Internet ads pay for the web site you're viewing, and are generally a fair trade-off for the information you're getting. Some ads, however, are so distracting and annoying that you just want to turn them off, particularly the animated ones. In Windows, I use Norton Internet Security to remove ads from the browser. Since there is no Linux tool (that I know of) to do the same, I had to find a few work-arounds, which I'll now pass on to you. I use Mozilla 1.6 as my web browser.

First, using Mozilla, go to "Privacy and Security" in the Preferences dialog, and checkmark "Block unrequested popup windows". You have now stopped unwanted popup windows from appearing in Mozilla.

There are two ways to block regular ads. The first is to put the URL of the ad site in your "hosts" file, referencing it to the same IP address as the Localhost: 

127.0.0.0   ads.fictitious.net

This will work with any browser. The second, again in Mozilla, is to right-click on the ad (most of them will be a picture, not text), and select "Block Images From This Server" from the resulting popup menu. Using these two methods, you can block some ad servers, while allowing the rest.

Finally, we have those annoying Flash ads. If you use Mozilla's new Firefox browser, you can add a plugin (see the Properties dialog) which replaces all Flash ads with a link that says something like "Click to play". The ad won't appear now unless you tell it to.

Playing Windows Media Video in Linux

There are codecs available that allow you to play back at least some ".wmv" video files in Linux. Once a matching codec is installed (I use version 5.2-1 of "w32codec"), it's easy to configure something like xine to play the video.

The Bottom Line

Generally, I've been very happy with my migration to Linux. I haven't solved all my problems yet, but I'm making good progress. In fact, I'm down to two minor issues, too small to really worry about for the moment. I'll mention them briefly, to give you some idea of what's left in my to-do list.

Sound. I'd like to get 5.1 surround sound to work on my Creative Labs Live sound card when playing a movie in Xine.

Printing. I have a 15 year old postscript printer that only prints in Linux using Laserjet emulation. Postscript works fine in Windows, but not in Linux, no matter what page descriptor file I use. I'm too cheap to buy a new printer, and besides, I'm still on the original toner cartridge. It should be good for at least another 15 years.

Finally...

The Windows Defector series is intended to educate and encourage people who are contemplating the switch from Windows to Linux (including me), so if you have any corrections, suggestions or solutions, please share them with everyone by sending a copy of your email to The Linux Gazette Answer Gang, rather than just to me. Flames and brickbats, however, you can continue to send just to me, as I don't want to clog-up the mailing list with all that extra volume. :-) .

[BIO] Tom has been a software developer since the early days of the Commodore 64, with such commercial classics as Prototerm-64 and Colorez-128, and has seen lots of operating systems come and go. Every one he's liked is either discontinued (OS/2) or out of business (Commodore Amiga). He currently likes Red Hat Linux, which won't be supported after April '04. As a result, we've been trying to get him to fall in love with Windows, but so far no luck.

Copyright © 2004, Tom Brown. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Help Dex

By Shane Collinge

These images are scaled down to minimize horizontal scrolling. To see a panel in all its clarity, click on it.

[cartoon]
[cartoon]

All HelpDex cartoons are at Shane's web site, www.shanecollinge.com.

[BIO] Part computer programmer, part cartoonist, part Mars Bar. At night, he runs around in a pair of colorful tights fighting criminals. During the day... well, he just runs around. He eats when he's hungry and sleeps when he's sleepy.

Copyright © 2004, Shane Collinge. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Ecol

By Javier Malonda

The Ecol comic strip is written for escomposlinux.org (ECOL), the web site that supports es.comp.os.linux, the Spanish USENET newsgroup for Linux. The strips are drawn in Spanish and then translated to English by the author.

These images are scaled down to minimize horizontal scrolling. To see a panel in all its clarity, click on it.

[cartoon]
[cartoon]
[cartoon]
[cartoon]
[cartoon]
[cartoon]

All Ecol cartoons are at tira.escomposlinux.org (Spanish), comic.escomposlinux.org (English) and http://tira.puntbarra.com/ (Catalan). The Catalan version is translated by the people who run the site; only a few episodes are currently available.

These cartoons are copyright Javier Malonda. They may be copied, linked or distributed by any means. However, you may not distribute modifications. If you link to a cartoon, please notify Javier, who would appreciate hearing from you.

Copyright © 2004, Javier Malonda. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Qubism

By Jon "Sir Flakey" Harsem

These images are scaled down to minimize horizontal scrolling. To see a panel in all its clarity, click on it.

[cartoon]

All Qubism cartoons are here at the CORE web site.

[BIO] Jon is the creator of the Qubism cartoon strip and current Editor-in-Chief of the CORE News Site. Somewhere along the early stages of his life he picked up a pencil and started drawing on the wallpaper. Now his cartoons appear 5 days a week on-line, go figure. He confesses to owning a Mac but swears it is for "personal use".

Copyright © 2004, Jon "Sir Flakey" Harsem. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


The Foolish Things We Do With Our Computers

By Ben Okopnik

Whack-A-Rack, or Impact-Based PC Repair

from Thomas Adam

[ ** This was posted to my LUG. I have obtained permission from Isaac, who said we can publish this for next month's edition of LG. ** ] 

 --- ISAAC CLOSE  wrote: 
 --- Thomas Adam  wrote:
> --- Paul Tansom  wrote: 
> 
> > Strangely enough I think that is all I remember of my assembly
> > programming on either 68000 or Z80 processors, although I still have
> > my faithful Z80 programming reference book somewhere.  Were computers
> > really more fun back then or am I just jaded now?!
> 
> Nope, it is all good fun. I have a unit at the moment, which is
> assembly programming on the 68HC05 (a motorola chip), although most of
> my assembly programming I learnt from my BBC Micro.

the ol' 6502 - 2MHz ?
cant remember nothing else tho ;)

funny...

A possibly well known trick to bring an hdd back to
life, is to smack it on the side with a soft hammer.
not too hard, but a whack indeed and presto. 
born again.

One time, I dropped a 14" Samsung monitor face down -
smack onto a concrete step and watched helplessly as it
rolled down a further twenty or so, in the pouring rain.
No problem, took it home, let it dry out a couple of
days, works fine - still gottit, but a bit 'chipped' on
the screen!

and...

My development server was found lid off in horrendous
rain, (old ibm p166), I payed five quid for it. 
(i166MMX/64MBRAM/2.5GBHDD/100MB/s-LAN)

Took it home, two days later switch on - fine ! 
even put a 40GB drive in it. Bios thort it was 8.5GB
(the old limit) but nope all 39GB useable. 

Then one day, I overclocked it, and it died! 
but came back to life strangley about a day or so 
later, I did nothing to it, just tried the power 
switch and it returned to life ? 

Then, another day, I set it up on the floor, dead.
put it on a table, fine. back on the floor, dead,
table, fine - wtf.

Then, sold it to a woman in Lewisham SE London,
she phoned me about a week later saying it bust.
So I went up their with spare bits. This damn computer
would not accept any hdd or cable! just ignored them
all. So, I took it back home. Plugged it in.
Guess what...

It is now sitting in my cupboard, last reboot 10 days
ago. Longest uptime (before I had to swap some plugs)
was over four months.

And the only computer I ever heard of that suffered from
the millenium bug was mine! (seen a few since) when I
booted my 30 day trial paint shop pro had expired by
about 32000 days, but worked fine for six months.

I could go on and on, but maybe another time.

Isaac

Rootless Wanderer Saved By SSH

from Heather Stern

Once upon a time I was logged into a system. I wasn't too careful about the terminal type setting - and I certainly wasn't careful enough - let's just say the setting was a little iffy, going from this nice FreeBSD box to my remote Solaris account. I didn't let this faze me since I know vi even in primitive keys mode without cursors, and I just needed something edited rather quickly.

As root. Whoops.

The passwd file, to fix a path. Carefully, carefully. Not carefully enough to avoid bumping into an extended key code just before the magic of ZZ took effect and saved the file...

...with the username root changed to the case sensitive and utterly different name Root from what shows in shadow, and guess who can't log in now. To put an even finer point on it, Solaris of that particular vintage has a few system functions that want to be the user root except - can you guess? Bet you can... by name, not by number. No such user. Bad things start happening like that great Garfield cartoon where all the things are going kerplooey and he races to the kitchen to see that all the warranties have expired.

Luckily having been logged in only moments ago I know what the problem is. Unluckily I know it will require root ... err... user 0 type access. Can I do it? ssh ... long pause ... authenticates me, and I am in. Hooray. THe normal authentication mechanism was one of the dying breed but ssh ignored it as I passed muster with my key. With sudo I raced to repair the damaged character and the day was saved.

I'll always be a fan of ssh and sudo. No doubt at all.

A Nice Clean Computer

from Tom Brown

A while back, I had the case off an old 486 "pizza-box" computer: removing something or adding something, I don't remember what. Anyway, while my back was turned, my son (who was 5 years old at the time) had come into the room. He was looking into the guts of the computer when his hand slipped on the glass of water he was holding, and the entire contents spilled into the machine. Only the fact that the computer was off, and the power cord pulled, saved us both from what would have been a dramatic light show.

Recognizing the better part of valor, my son vanished from the room, taking his now-empty glass with him.

The first thing I did was carry the computer to the nearest sink, and pour the water out of it. There was quite a lot, as the glass had been nearly full. From there, I disassembled every last part of the machine, and spent the rest of the afternoon applying my wife's hair drier on the soaked motherboard, memory, and assorted IDE cards. Lucky it was water, and not something like juice or soda! Surprisingly enough, when everything was dry, and reassembled, the computer worked, although, periodically, the machine would refuse to boot, and I had to push and pull on the components a bit, flexing the motherboard until it booted. Guess I missed a spot.

As for my son, he never again went near a computer with a drink in his hand.

[ If you have a story about something foolish or ingenious you did to your computer, send it to articles@linuxgazette.net. -Ben ]

Ben is the Technical Editor for Linux Gazette and a member of The Answer Gang; this month, he's also standing in for the Editor-in-Chief, Mike Orr, who is away on vacation.

picture Ben was born in Moscow, Russia in 1962. He became interested in electricity at age six - promptly demonstrating it by sticking a fork into a socket and starting a fire - and has been falling down technological mineshafts ever since. He has been working with computers since the Elder Days, when they had to be built by soldering parts onto printed circuit boards and programs had to fit into 4k of memory. He would gladly pay good money to any psychologist who can cure him of the resulting nightmares.

His subsequent experiences include creating software in nearly a dozen languages, network and database maintenance during the approach of a hurricane, and writing articles for publications ranging from sailing magazines to technological journals. After a seven-year Atlantic/Caribbean cruise under sail and passages up and down the East coast of the US, he is currently anchored in St. Augustine, Florida. He works as a technical instructor for Sun Microsystems and a private consultant. His current set of hobbies includes flying, yoga, 18th century reenactment, blacksmithing, sea-shanty singing, and writing; his Palm Pilot is crammed full of alarms, most of which contain exclamation points.

He has been working with Linux since 1997, and credits it with his complete loss of interest in waging nuclear warfare on parts of the Pacific Northwest.

Copyright © 2004, Ben Okopnik. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Home Folder Server For Windows Clients

By Avinoam Levkovich

One of the strategies to protect the data on user's personal computer is using a Home-Folders Server. This server contains folders for each user where the user can save his precious data, the server is backed up every night. At login, the Home-Folders Share (which contains your home folder) is mounted on the local machine, and the user can access it like any other local drive.

Home-Folders Server has a big overhead for the IT staff. Managing the ownership, shares, quota, permissions, and the never ending changes isn't one of the most pleasant tasks for any Sys-Admin.

The story begins when my organization old Home-Folders Server started showing signs of retirement wishes, we decided that it is time to build a new Home-Folders server. We started looking for a solution that will take the management overhead from the IT stuff, since our budget was low we wanted cheap but reliable system. Naturally, we started thinking about building a Linux server. We wanted this system to perform the following tasks:

  1. This system will be integrated into the organization's existing Win-2K active directory infrastructure.
  2. The system should function automatically. When we add a new user to the domain, the system will automatically create his home folder, grant the appropriate permissions and configure the user's quota.
  3. We will map the home-folder by using login scripts (KIX).
  4. The System will monitor the Server RAID-System, when the RAID is out of sync (damaged disk, Bad Controller, etc.) the script send a warning e-mail to the IT staff.

Since our budget was low, we decided to save money and still get good performance by using a new desktop PC (P4 1.6GHZ, 1GB RAM). To make the system reliable we decided to use four HDs (IDE, 120GB each) configured as RAID-5, for the Home-Folders partition. All other system partitions will use two HD (IDE, 12GB each) with RAID-1 (mirror). To get the extra IDE controllers I used PROMISE 133TX2, IDE Card (PCI), which works great with RedHat.

The Home-Folder System Installation and Configuration

After installing Linux (we used Redhat) and configuring the RAID system, take the following steps to finish the configuration of the Home-Folders Server:

  1. Install and configure the Samba server, share the Home-Folders partition with read/write permission (we will limit the access to the users' folders by using the system permissions.)
  2. Configure Winbind. Winbind is part of the Samba package which makes the integration to the windows domain easy.
    By using Winbind, Windows Users can access the Linux server using their logon credentials. Winbind verifies the user with the domain controller like any other Windows server. You can find more info on Winbind installation in this article : http://us2.samba.org/samba/docs/man/winbindd.8.html
    After installing Winbind, check its functionality by running the command: 
    # getent passwd
    The output should be the list of users in the domain. If you do not receive this output, check your Winbind configuration.
  3. Configure quota support for the Home-Folders partition. You can find more info about quota configuration here: http://www.tldp.org/HOWTO/Quota.html
    Next, plan and decide how much space you wish to grant to each user, create a template user and assign a quota equal to the amount of space you decided. Later on we will use this user as a quota template.

    Note: this step is optional and only required if you want to use the quota system.

Home-Folders Creator Script

The following script is the heart of the system, the script retrieves the domain users list from the domain controller server into a file and removes all the unneeded data from the list. At this stage the system verifies that each user in this list owns a home-folder. If the user already has a home-folder the system write the char "." to the stdout and moves on, if the user is a new user and he still doesn't have a home-folder, the system will create a folder (the folder name will be the same as the username), grant ownership to the user, and apply the quota for this folder by copying the quota from the template quota user to this new user.

The system will log the new users home-folder creation to the system log file (/var/log/messages).

The Home-Folders creator script can be found here. You need to change the following parameters to reflect your server configuration:

HOME_FOLDERS_PATH - Assign the path to the Home-Folders Directory/Partition, it is essential to put the character "/" at the end of the path (e.g. /home/).

SEPERATOR - Assign the Winbind separator as it configured in the smb.conf file.

TEMP_USER - (OPTIONAL) if you want to use quota, you should uncomment this variable and Assign the username you created to act as a quota template. if so please remember to uncomment the line "edquota -p $TEMP_USER $DOMAIN$SEPERATOR$Folder_Name"

The RAID system watchdog script

The following script creates an endless loop that check the RAID system every 5 minutes, if the RAID is out of sync (damaged disk, Bad Controller etc..) the script will send an e-mail to a predefine mail address ( change the MAIL variable to reflect your mail address).

you can use this script as an independent RAID WatchDog for your other RAID-Systems.

In order to start this script automatically after reboot, you can add the path to the script to your rc.local file. The script can be found here.

Make the system function automatically

To automate the system you should execute the Home-Folders creator script as root at predefined intervals. By adding the following line to the root's cron jobs (using "crontab -e"), the Home-Folders script will execute every hour. (Change the script path to match your configuration.) 

*/59 * * * * /etc/Home-Folders-creator.sh

Mapping the Home-Folder to the users during the logon process

By using a simple logon scripts system (I use KIX) you can map the Home-Folder Samba share during the user login process.

[BIO] Avinoam Levkovich is an RHCE in Israel, currently working as the Linux Sys-Admin at the Rambam Medical Center.

Copyright © 2004, Avinoam Levkovich. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Simple Joystick control of a servo motor with RTAI/Linux

By Pramode C.E

The analog joystick which plugs onto the PC game port is a cool little device - you don't need to be a hardware wizard to learn how it works, and you can make it do fun and absolutely useless stuff like turn a stepper or servo motor. This article describes an experiment which I did with a joystick and a Futaba S2003 servo motor, both controlled by the real time operating environment for Linux called RTAI. Readers who are not familiar with RTAI might like to refer to the introductory article I had written earlier before continuing.

The Joystick

If you are game-crazy, you are sure to have used one. As far as electronics is concerned, it is a very primitive device - so is the game port which it plugs into. You will find adequate hardware descriptions here. The Linux IO-Port Programming Mini-HOWTO also provides sufficient information to get started with hacking the joystick.

Reading the buttons

Your first joystick programming assignment should be reading the state of the buttons. For this, you have to know the ISA port address which the gameport uses. Loading the standard Linux joystick driver (you will have to modprobe three modules - joydev, ns558 and analog) and doing `cat /dev/ioports' on my ASUS A7N266VM motherboard showed this to be 0x200.

The state of two of my joystick buttons is encoded in bits D4 and D5 of the 8 bit value returned by an `inb' on 0x200 (D0 is least significant bit and D7 is most significant bit). If the value is 1, the button is in the `released' state and if it is 0, the button is in the `pressed' state. Here is a small program which tests this out:

Listing 1 


#include <asm/io.h>
#define JS_PORT 0x200

main()
{
    iopl(3);
    while(1)
        printf("%x\n", (inb(JS_PORT) >> 4)&1);
		
}

Reading the X and Y positions

Moving the joystick results in a potentiometer turning - the potentiometer is connected to the game port, which contains a 555 timer based circuit. A simple `outb' to 0x200 (the value written doesn't matter) will result in the circuit getting `reset' - now a read (ie, an `inb') from 0x200 will yield a bit pattern whose D0 and D1 bits are 1's. Keep on reading - after a short time these bits become zero. Measure the time it takes for the bits to become zero. Take the measurements with the joystick at the extreme left, middle and extreme right endpoints of the X axis as well as the top, middle and bottom points of the Y axis as part of a `calibration' process. Now, whatever be the position of the joystick along the X-Y axes, measuring the time it takes for the D0 (X axis) and D1 (Y axis) bits to become zero's after a `reset' (note, we `reset' by writing something to 0x200) should help us find it out (assuming that time varies linearly with distance between the middle and left/top as well as middle and right/bottom endpoints - which I really haven't verified).

Here is a program which measures the time it takes for the X-axis bit to become zero after a reset. It uses the `time stamp counter' which is a 64 bit counter available on all machines with, I believe, a Pentium and above CPU. If you have a 1GHz CPU, the timer gets incremented at a rate of 1,000,000,000 per second. My Athlon XP CPU runs at a clock speed of 1462.904 MHz (read from /proc/cpuinfo) - with this information, it is easy to compute the time elapsed between any two points in your program. The time stamp counter (TSC) can be read using a macro called `rdtsc' defined in the file /usr/src/linux/include/asm/msr.h.

Listing 2 


#include <asm/io.h>
#include <asm/msr.h>

#define JS_PORT 0x200
#define CPU_HZ 1462904000

void  trigger(void)
{
    outb(0x0, JS_PORT);
}

main()
{
    unsigned int low1, high1, low2, high2;
    iopl(3);
    trigger();
    rdtsc(low1, high1);
    while(inb(JS_PORT) & 1);
    rdtsc(low2, high2);
    printf("low1=%u, high1=%u, low2=%u, high2=%u\n", low1, high1, low2, high2);
    printf("low2 - low1 = %u\n", low2 - low1);
    printf("in ms = %f\n", (((double)(low2-low1))/CPU_HZ)*1000);
}

The program should be compiled like this: 


cc -I/usr/src/linux/include -O2 xmeasure.c
I got readings of 0.0262ms, 0.68ms and 1.60ms for the left, middle and right positions.

One trouble with this crude form of analog-to-digital conversion is that you have to sit in a loop waiting for the bits to drop to zero - this burns up CPU cycles. A better design would have been for the joystick hardware itself to perform the A-D conversion and send the resulting numbers to the PC - thus avoiding lots of software overhead.

Using a periodic RTAI task to sense joystick position

My experiment is this: I have a servo motor connected to the parallel port. The servo is not capable of rotating the full 360 degrees - it describes an arc of about 180 degrees. When I turn the joystick left, the servo also moves to the left end of the arc. When the joystick is in the `middle' position, the servo positions itself near the centre of the 180 degree arc and when the joystick moves towards the right end, the servo also moves towards the right end of the arc. Note that I try to sense only three joystick positions - left, middle and right.

The picture above shows two servo motors - the one at the bottom serving to rotate the platform resting on it - it is this servo which I will be moving with the joystick.

The idea is simple. A periodic task (period .33 milliseconds) monitors the joystick. At the first activation of this task (lets say at time 0), we `trigger' the game port (by writing to it) and assume that joystick position is `LEFT'. The next activation of the task would be at 0.33 milliseconds. If reading from the game port tells us that the X axis bit (D0) is still set, we assume that the joystick is in the `MIDDLE' position. The next activation of the task would be at 0.66 milliseconds - but we are not interested in checking the X axis bit at this point - we will take it that the joystick is in the `MIDDLE' position if the bit stays high for a period between 0.33 and 0.99 milliseconds (note that the `bit-high' times obtained experimentally were 0.026, 0.68 and 1.60 milliseconds respectively for extreme left, middle and extreme right positions). The next activation would be at 0.99 milliseconds - if bit D0 still stays high, we assume that the joystick is in the `RIGHT' position. Only at this point are we sure of the actual position of the joystick - we shall set a global variable, `joystick_position' to LEFT, RIGHT or MIDDLE.

Now we come to the servo motor control part - which is fairly simple. A hobby servo motor requires a `control pulse' on its white wire. The total on-off time of the pulse should be around 20 milliseconds - it is the 'on' time which actually controls the servo's position. My servo moves to one end of a 180 degree arc for an 'on' time of about 0.5 millisecond and moves to the other end for an 'on' time of about 2.2 seconds. A separate RTAI task controls the generation of this signal. A global array called `on_time' maintains the three 'on'-time values which would move the servo to the left, middle and right points of its arc. The servo task makes pin 3 of the parallel port (to which the servo's control wire is connected) high for a period of on_time[LEFT] if the current joystick position is `LEFT' - similarly for MIDDLE and RIGHT also. The 'off' time of the control pulse is stored in a variable `off_time' and is computed in such a way that the total 'on' plus 'off' time is around 20 milliseconds.

[Listing 3] 


static void 
pwm_servo(int t)
{
    /* Servo is controlled by
     * signal on pin 3 of LPT1
    */
    while(1) {
        outb(2, LPT1_BASE); /* Pin 3 high */
        rt_sleep(on_time[joystick_position]);
        outb(~2, LPT1_BASE);
        rt_sleep(off_time);
    }
}

Conclusion

It has been fun playing with the joystick. I would like to know if there is a good method to monitor the joystick position continuously without loading RTAI too much (by increasing the timer frequency or resorting to busy loops) - let me know if you come across anything interesting. I can be contacted via my home page at pramode.net.

[BIO] I am an instructor working for IC Software in Kerala, India. I would have loved becoming an organic chemist, but I do the second best thing possible, which is play with Linux and teach programming!

Copyright © 2004, Pramode C.E. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


Designing Simple front ends with dialog/Xdialog

By Sunil Thomas Thonikuzhiyil

1) Introduction

This article introduces dialog and Xdialog for building simple front ends to shell scripts. It assumes that you are familiar with shell programming.
The latest version of this document can be found at http://gnubox.dyndns.org:8080/~sunil/dialog.php.

dialog is a utility for building console-based front ends. Xdialog is a similar program for X. Both programs are more or less compatible and easy to program. Dialog is shipped with most GNU/Linux distributions. If you want to build from sources, a tarball can be obtained from here. Xdialog is available from here.

Both of these programs are free software and run on a variety of *nix platforms. Most of the examples given in this tutorial are adapted from examples given along with dialog sources.

2) Basics

Here is the first dialog script I tried. It displays a simple YES/NO box. 
#!/bin/bash
DIALOG=${DIALOG=dialog}

$DIALOG --title " My first dialog" --clear \
        --yesno "Hello , this is my first dialog program" 10 30

case $? in
  0)
    echo "Yes chosen.";;
  1)
    echo "No chosen.";;
  255)
    echo "ESC pressed.";;
esac

Copy the above lines to a file say yesno.sh and give executable permission to it. 

$chmod u+x yesno.sh

Now try running the program. 

$./yesno.sh

A screen-shot of the above program is given below.
yesno box
Now try changing the line. 

 DIALOG=${DIALOG=dialog}
to 
DIALOG=${DIALOG=Xdialog}

Try running it from an xterm. I got the following output.
xyesno box

Let us have a detailed look at the above program. The first line is basically a comment which also indicates that bash shell is used to run this program. 

DIALOG=${DIALOG=dialog}

The above line sets the variable DIALOG to the value 'dialog'. The actual dialog box is drawn by the following line. 

  $DIALOG --title "My first dialog" --clear \
        --yesno "Hello, this is my first dialog program" 10 30

Options used are
--title This option sets title of your box
--clear This option clears the screen before drawing
--yesnobox This draws the box with the text given inside the box.

The text to be printed inside yesnobox is given in double quotes. The text wraps depending on width of the box. You can use \n to force a new line. Last 2 numbers specify width and height of the box. You can move between "yes" and "no" using tabs.

The dialog program now waits for user input. When you press enter on "yes" or "no" or if you press escape key the program returns and the return value is available on shell variable $? which you can process further.

2) Reading input

The following program reads a string you input and prints it back. 

#!/bin/sh
DIALOG=${DIALOG=dialog}
tempfile=`tempfile 2>/dev/null` || tempfile=/tmp/test$$
trap "rm -f $tempfile" 0 1 2 5 15

$DIALOG --title "My input box" --clear \
        --inputbox "Hi, this is a sample input box\n
Try entering your name below:" 16 51 2> $tempfile

retval=$?

case $retval in
  0)
    echo "Input string is `cat $tempfile`";;
  1)
    echo "Cancel pressed.";;
  255)
    if test -s $tempfile ; then
      cat $tempfile
    else
      echo "ESC pressed."
    fi
    ;;
esac

Try running the program under console and under X ( after changing dialog to Xdialog as above). See the results.
input box

This program is slightly more complex than our previous yesno box program. The following lines set up a temporary file: 

tempfile=`tempfile 2>/dev/null` || tempfile=/tmp/test$$
trap "rm -f $tempfile" 0 1 2 5 15

The first line above tries to create a temporary file using the utility tempfile. If it fails, a temporary file is manually set up in /tmp. The second line above sets up a trap routine. When the script exits (either normally or abnormally) the trap removes the tempfile. The numbers shown are the signals that will be trapped.

dialog is then invoked as below: 

$DIALOG --title "My input box" --clear \
        --inputbox "Hi, this is a sample input box\n
         Try entering your name below:" 16 51 2> $tempfile

The dialog program writes its output to the standard error by default. Hence the input string you enter is echoed to standard error which we are redirecting to our tempfile. You can capture the entered text from tempfile for further processing.

3) Building a menu

Try the following program both in console and X (after changing dialog to Xdialog as before): 

#!/bin/sh
DIALOG=${DIALOG=dialog}
tempfile=`tempfile 2>/dev/null` || tempfile=/tmp/test$$
trap "rm -f $tempfile" 0 1 2 5 15

$DIALOG --clear --title "My  favorite HINDI singer" \
        --menu "Hi, Choose  your favorite HINDI singer:" 20 51 4 \
        "Rafi"  "Mohammed Rafi" \
        "Mukesh" "Mukesh" \
        "Kishore" "Kishore Kumar" \
        "Saigal" "K L Saigal" \
        "Lata"  "Lata Mangeshkar" \
        "Yesudas"  "K J Yesudas" 2> $tempfile

retval=$?

choice=`cat $tempfile`

case $retval in
  0)
    echo "'$choice' is your favorite hindi singer";;
  1)
    echo "Cancel pressed.";;
  255)
    echo "ESC pressed.";;
esac

The results are as below
Menu box
menu box

The logic is exactly similar to inputbox. We redirect the choice you have selected to a tempfile and then process return value of dialog and contents of the tempfile.

4) Radiolist and Checklist

Radiolists and checklists can be programmed just like menus. A simple radio list example is given below. 

#! /bin/sh
DIALOG=${DIALOG=dialog}
tempfile=`tempfile 2>/dev/null` || tempfile=/tmp/test$$
trap "rm -f $tempfile" 0 1 2 5 15

$DIALOG --backtitle "Select your favorite singer" \
	--title "My favorite singer" --clear \
        --radiolist "Hi, you can select your favorite singer here  " 20 61 5 \
        "Rafi"  "Mohammed Rafi" off \
        "Lata"    "Lata Mangeshkar" ON \
        "Hemant" "Hemant Kumar" off \
        "Dey"    "MannaDey" off \
        "Kishore"    "Kishore Kumar" off \
        "Yesudas"   "K. J. Yesudas" off  2> $tempfile

retval=$?

choice=`cat $tempfile`
case $retval in
  0)
    echo "'$choice' is your favorite singer";;
  1)
    echo "Cancel pressed.";;
  255)
    echo "ESC pressed.";;
esac

A screen shot is shown below.

radiolist

For trying out checklist just change --radiolist option in the above program to --checklist.

5) Building a Gauge

A gauge based on dialog can be used to indicate progress of your program. Building a gauge is slightly tricky. Look at the following example: 

#!/bin/sh
DIALOG=${DIALOG=dialog}

COUNT=10
(
while test $COUNT != 110
do
echo $COUNT
echo "XXX"
echo "The new\n\message ($COUNT percent)"
echo "XXX"
COUNT=`expr $COUNT + 10`
sleep 1
done
) |
$DIALOG --title "My Gauge" --gauge "Hi, this is a gauge widget" 20 70 0

Here the dialog program gets its input from the code shown within the parentheses. This code emits the number to be used for gauge and the message to be shown. The message to be shown in the gauge box must be surrounded by echo "XXX". The screen-shot of a gauge is shown below.
gauge

6) File selections

Code for a typical file selection dialog box is shown below. 

#!/bin/sh
DIALOG=${DIALOG=dialog}

FILE=`$DIALOG --stdout --title "Please choose a file" --fselect $HOME/ 14 48`

case $? in
	0)
		echo "\"$FILE\" chosen";;
	1)
		echo "Cancel pressed.";;
	255)
		echo "Box closed.";;
esac

file selection

Please note that the above program uses a different technique to capture the selected file. As mentioned previously all outputs from dialog is sent to standard error by default. However --stdout option can be used to send the output information to standard output which in turn can be assigned to a variable. This trick can be used in the case of other dialog boxes such as menubox yesnobox etc.

The file selection dialog presents 2 panes. You can use Tab key to switch between panes and space key to select a file. It is also possible to type into the input box of files select dialog.

7) Calendar and time boxes

a) Calendar

A calendar box displays month, day and year in separately adjustable windows. If the values for day, month or year are missing or negative, the current date's corresponding values are used. You can increment or decrement any of those using the left-, up-, right- and down-arrows. Use vi-style h, j, k and l for moving around the array of days in a month. Use tab or back tab to move between windows. If the year is given as zero, the current date is used as an initial value. On exit, the date is printed in the form day/month/year. 

#!/bin/sh
DIALOG=${DIALOG=dialog}

USERDATE=`$DIALOG --stdout --title "CALENDAR" --calendar "Please choose a date..." 0 0 7 7 1981`

case $? in
  0)
    echo "Date entered: $USERDATE.";;
  1)
    echo "Cancel pressed.";;
  255)
    echo "Box closed.";;
esac

calendar

b) Time

The time dialog box allows you to select time. Try out the following program and see how it works. 

#!/bin/sh

DIALOG=${DIALOG=dialog}
USERTIME=`$DIALOG --stdout --title "TIMEBOX" --timebox "Please set the time..." 0 0 12 34 56`

case $? in
  0)
    echo "Time entered: $USERTIME.";;
  1)
    echo "Cancel pressed.";;
  255)
    echo "Box closed.";;
esac

time

8) Other Features

Xdialog has some additional features such as tree-view, range-box, edit-box, etc. Please look here. Dialog man page has interesting information of some other options such as password box, tailbox etc. Also there are options for changing colors, shadow etc.

9) Tips

You can choose between dialog and Xdialog at run time using the following code snippet: 

   if [ -z $DISPLAY ]
   then
   DIALOG=dialog
   else
    DIALOG=Xdialog
   fi

Try this program on console as well as under X and see the difference. 

 #!/bin/sh
 if [ -z $DISPLAY ]
 then
 DIALOG=dialog
  else
   DIALOG=Xdialog
  fi
 $DIALOG --yesno "Is this fun" 0 0

10) References

1) Manual page for dialog

It is a must read if you are planning to write some useful dialog scripts. There are several other options which allow you to modify the look and feel.

2) Dialog examples at http://www.fifi.org/doc/dialog/examples/.

All the examples in this tutorial are modified versions of examples found here. If you have Debian GNU/Linux the examples are available at /usr/share/doc/dialog/examples.

3) Thomas Dickey's dialog page: http://dickey.his.com/dialog/

4) Vincent Stemen's dialog page http://hightek.org/dialog/.

This page has comprehensive information on various dialog versions.

5) Xdialog documentation at http://thgodef.nerim.net/xdialog/doc/index.html.
This page has exhaustive information on Xdialog.

[BIO] I work as consultant information technology at the Kerala Legislative Assembly Trivandrum India. I have been hooked on Linux since 1996. I have a Masters in Computer Science from Cochin University. I am interested in all sorts of operating systems. In my free time I love to listen to Indian classical music.

Copyright © 2004, Sunil Thomas Thonikuzhiyil. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004


The Back Page

By Ben Okopnik

This month, our Editor-in-Chief, Mike Orr, is away at some conference where he is wrestling pythons. Or some Python conference followed by wrestling... he sounded a bit strangled on the phone, so it was a little difficult to tell - but whatever it is, it involves his hobbies. While he's gone, I've volunteered to do the Editor-in-Chief's duties, including publishing - and as you can imagine, I had hoped that this month would pass quietly and everything would roll out on schedule.

Say, does anyone else hear that hollow laugh?...

Our Answer Gal, Heather Stern, who is responsible for a large chunk of the LG production process, had a series of hardware problems that grew like Topsy to encompass not only her entire system but eventually involved her ISP and the name registrar (!). I mean, really, sans peur et sans reproche is one thing, but sans email at production time???... believe it or not, she still managed to get her work done as well as contribute some material for our regular columns, although, of course, it was all unavoidably delayed. So life goes, gentle readers. You have my apologies for LG being a bit late this month - we usually try to publish within a few days of the 1st.



While I have the chance to ramble - this month, I celebrated my birthday, one I share with Sergei Rachmaninoff, Abraham Maslow, Otto von Bismark, William Harvey, and, uh, "Method Man". April 1st, the day that the internal combustion engine was patented and that color television was first sold (and also the day the yo-yo was introduced to the American public), is "celebrated" world-wide as "April Fools Day", the day when people pull pranks and give gag gifts to each other - something I've been fortunate enough, or perhaps large enough to avoid. As my Web page says, "creative answers will be graded appropriately, with bastinado being reserved for the wittiest and applause for the most charming. Note that a combination of the two is hereby explicitly not excluded."

To make a long story short (for the hecklers in the back of the room yelling "too late!", you just quiet down), I ended up going to dinner with a client of mine who insisted that I should do something special for myself, at a very nice local restaurant called "Fusion Point". (Chris is also a good friend as well as being my yoga teacher.) While munching on the gourmet fare, we got into a deep philosophical discussion (as we often do), and I happened to mention Linux, which he had never heard of. Once I described some of the dynamics of the community and the way it came about, Chris looked at me and said: "You see, this is the exactly the kind of progress in the direction of enlightenment that we've been talking about. Despite the wars, the hatred, all the evils of the human condition, there is an underlying and irresistible movement in that direction - and it's cumulative." (This is a paraphrase because I don't recall his exact words, but it's close.)

This is, indeed, the way that I see Linux. It goes beyond just the OS, beyond the free tools; it is a way for many people whose abilities would remain hidden and unused without that necessary leverage to become empowered, a way for those whose lack of money has stifled their ability to express their creativity to bring it out to the world. It's not a cure-all for all the existing ills by any means - but it is certainly a step in the right direction.

My best wishes and congratulations to all of you who are making your way toward the light. I take great joy and pride in being able to contribute to that progress, in whatever way I can.

Ben is the Technical Editor for Linux Gazette and a member of The Answer Gang; this month, he's also standing in for the Editor-in-Chief, Mike Orr, who is away on vacation.

picture Ben was born in Moscow, Russia in 1962. He became interested in electricity at age six - promptly demonstrating it by sticking a fork into a socket and starting a fire - and has been falling down technological mineshafts ever since. He has been working with computers since the Elder Days, when they had to be built by soldering parts onto printed circuit boards and programs had to fit into 4k of memory. He would gladly pay good money to any psychologist who can cure him of the resulting nightmares.

His subsequent experiences include creating software in nearly a dozen languages, network and database maintenance during the approach of a hurricane, and writing articles for publications ranging from sailing magazines to technological journals. After a seven-year Atlantic/Caribbean cruise under sail and passages up and down the East coast of the US, he is currently anchored in St. Augustine, Florida. He works as a technical instructor for Sun Microsystems and a private consultant. His current set of hobbies includes flying, yoga, 18th century reenactment, blacksmithing, sea-shanty singing, and writing; his Palm Pilot is crammed full of alarms, most of which contain exclamation points.

He has been working with Linux since 1997, and credits it with his complete loss of interest in waging nuclear warfare on parts of the Pacific Northwest.

Copyright © 2004, Ben Okopnik. Copying license http://linuxgazette.net/copying.html

Published in Issue 101 of Linux Gazette, April 2004