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From The Readers of Linux Gazette

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FvwmCommand (FvwmCommandS)

Fri, 15 Nov 2002 17:17:20 -0100
Hans Borg (Hans.Borg from Physics.umu.se)
with comments by Heather Stern (LG Technical Editor) and Thomas Adam (The LG Weekend Mechanic)

Hi all,

Have tried to find a help forum for Fvwm* stuff, but can't find any. My be just tipping me of one is enough.

The problem: Have made an application using FvwmCommand that works fine when running under /root (super user, SU). However, when running under a "normal" user it fails by the FvwmCommand fifos.

[Thomas] I use nothing but fvwm :-) I love it. It would be useful to know which version of fvwm you're running.

My understanding: The FvwmCommandS sets up 2 fifos (C,M) in /var/tmp and always get the permission prw-------. Those fifos doesn't seem to be accessible from none SU.

[Thomas] Yeah -- I checked the Changelog file for fvwm version >=2.3.0, and there was a bug within the FvwmCommand module. However, as of version 2.3.6, it was fixed. I'd upgrade to the latest stable release.

When trying not SU, always get the report:

No such file or directory FvwmCommand error in opening message fifo: Permission denied.

May be this is deliberately from some security point of view, but on the other hand FvwmCommand is "x for all" in my default installation.

Best regards

[Thomas] As Heather goes on to explain, it is most likely a umask problem.
I'm a fvwm fan myself, but I've not used the FvwmCommand module. Generally I just put things on the menus as Exec calls.
However, it sounds like a umask problem; and possibly a permissions problem in the filesystem. /var/tmp, rather like /tmp, should be permissions 1777 (sticky-bit, everybody can see and write and stat things in the directory). The permissions your file got would be sufficient to defend it from other accounts reading it, but should allow the creating account to work with it. Also note that it's not executable; you weren't trying to create a script and then run it, were you? -- Heather
[Thomas] But that's what FvwmCommand can do heather! It's supposed to do that :-)
Is it also supposed to refuse to do it if the result is not marked executable?
For doing, um, dynamic things I like to have a tmp under my homedir, which belongs only to me (mode 0700) so I can do strange things but I don't subject myself to possible nosy other users. Mind you, I don't usually have other users to worry about, but what the heck; I plan some things here that may get put in production elsewhere. -- Heather

Thanks for your answers and appologies for my late
response. Have been away we no net capabilities.

I agree that it looks like a permission problem as is actually reported. There should be no problem with the /var/tmp directory permissions. They are both "rwx" (7) for all.

You don't mention if it's sticky (shows drwxrwxrwt with ls) -- Heather

The problem seems to be related to FvwmCommandS that sets up (I guess) the two Fifos and also sets the permission to prw-------. By the way, what does "P" stand for.

p stands for named pipe. Stdout (standard out) of one process may be set to feed into a pipe, and the program attached to pick up stdin (standard input) from that pipe can use that to do whatever it needs to do next.
Both the programs should have the permission to reach the pipe that has been created; the umask of the fvwmcommand process is probably restricted to prevent nasty side effects. -- Heather

Have tried after FvwmCommandS is spawned to (as SU) change the fifo permissions by all sorts of combinations with no luck. Typically I can get to prwSrwSrw-. In chmod I used "s" but comes out as "S".

That's because it had no execute permission; since the "Suid" shares a space with the "eXecute" bit, a way was needed to show that both are set, or only one of them,
execute but not suid: for owner and group, the first two triplets: rwx
execute AND suid: for owner and group: rws
not execute, but suid. This doesn't make sense for most purposes: for owner and group: rwS
execute but not sticky: for "other", the third triplet: rwx
execute and sticky: for other: rwt
not execute, but sticky. again it's rare for this to be reasonable: for other: rwT
Now, since the suid, exec, and sticky bits don't affect the read or write, those "rw" could really be any of "r-" "-w" "--" or "rw". -- Heather

My version of FvwmCommand is 2.4.7. I do not know what, or how to find out the version of FvwmCommandS.

I do not know that either. Perhaps Thomas Adams or one of the other Answer Gang members can help further. -- Heather

Thanks a lot for the information on permissions. Some of them were new
to me.

Honestly, I have to tell that I have rewritten the application in order not to use FvwmCommand, but it is still interesting to know where the problem sits. It may be useful in the future.

Just for testing I have done the following (may be someone can do the same ?).

  1. I have set the permissions as (a lot shouldn't be needed, but just for test): FvwmCommand: -rwsr-sr-x /var: drwsrwsrwx /var/tmp: drwsrwsrwt
  2. FvwmCommandS is spawned by fvwm95 (using that). When spawned I changed (as root) the two fifos permissions to: prwsrwsrwx
  3. From an xterm I run: FvwmCommand Restart fvwm95. Works when logged in as root but not as !root user.

Well, as having rewritten the application it is no longer of utmost importance.

The Answer Gang has been of a lot of help in the past. Thank you all.

Best regards

During this thread I cc'd the Answer Gang back in so the entire Gang can help you out here. Any one of us could go underwater with complicated questions, so we do not "assign techs" to help anybody all alone. Good thing too - nice to have Thomas confirm what I was groping around in the dark about...
... and that's where it comes to you, dear readers. Hans solved his problem, by avoiding it. But if anyone happens to know what it's really up to - was it really a bug in that version, does it really work now? If anyone else out there is using fvwmcommand actively, drop us a line and let us know what you're doing with it. I presume, making FVWM a little more fun :)
Other articles or replies about making your favorite window manager do cool and weird things are also welcome. If we get enough maybe it could be the month of "The Truly Cool Things We Did To Our Computers" -- Heather

Installing Redhat on Dell X200 laptop (via 1394 CD)

Thu, 19 Dec 2002 14:58:35 -0700
Montgomery, Jim (jmontgomery from peakdatallc.com)

Please help me install Redhat 7.3 on my Dell X200 laptop. This machine has a firewire CD from which I am able to start the install process. However, the install process soon asks for the device from which to do the install (NFS, FTP, Hard disk, etc.).

No option is given for CD. It looks my BIOS can see the 1394 CD but Redhat cannot. I've looked in all the obvious places for 1394 firewire drivers (Redhat, Dell, Linux documentation and discussion sites). Please help. NFS/FTP boot is not an option.

Thanx, Jim Montgomery

[Heather] For that matter, if our readers know any distro that would cleanly install from a firewire CD, let us know. Distro vendors - look forward to more questions like this!


Thanks for the viewer hints

Wed, 27 Nov 2002 19:23:09 EST
Jack (JRook78123 from aol.com)

I forgot to tell the lads and lassies at Linux.......I got the .max viewer online and downloaded it.......Now I can view my nieces scans without having to fiddle with them......

Again and again, THANKS!

Jack - Chicago

The last word on "daemon"

Wed, 4 Dec 2002 09:56:00 +0100 (CET)
Maurizio Loreti (loreti from pd.infn.it)

I have read on the December Linux Gazette (mailbag) another letter about the etimology of "daemon". Usually for this kind of things the ultimate source of knowledge is "The Jargon File" by Eric S. Raymond, aka ESR (aveilable at the URL http://www.tuxedo.org/~esr/jargon) .

At this point he repeats the entry, but you can find it online at: http://tuxedo.org/~esr/jargon/html/entry/daemon.html
The jargon file entry was mentioned in the starter to this thread, which began in the October issue when someone confused about Kylix made a wildly incorrect guess about the origin of "daemon" and was immediately fed all sorts of tasty bits by The Answer Gang. I thought the timing was quite excellent as it arrived perfectly for Halloween. http://linuxgazette.net/issue83/tag/1.html
It has since seen replies in November's and December's mailbag http://linuxgazette.net/issue84/lg_mail.html http://linuxgazette.net/issue85/lg_mail.html which remove the haze of years that a glossary entry generally summarizes out of existence, to describe current usage only. The Jargon File doesn't always do this, but the information lost by not being quite common enough "common knoqledge" before this began to be set down as bits (and eventually paper) sadly does the glazing over quite well enough.
"ultimate" is a strong word and frankly I rarely use it for anything. Anyone who's been in this business long enough knows that to depend upon only one source for your research isn't really "ultimate" at all, and I'm pleased to have drawn some historians out of the woodwork with more complete info than the Gang pulled out of our wizard hats at the end of September.
In fact, I think the Jargon File maintainers may well like to add details from the etymology-of-daemon thread updates to their entry. To make it more likely, I've cc'd their maintainer list. :) Hi Eric, and everybody :)
As of press time, I haven't seen an update to this entry in the Jargon File as a result. No worries. It's probably because I didn't follow their posting guidelines more closely... -- Heather


You can mail submissions for the Jargon File to jargon@snark.thyrsus.com.

We welcome new jargon, and corrections to or amplifications of existing entries. You can improve your submission's chances of being included by adding background information on user population and years of currency. References to actual usage via URLs and/or Google pointers are particularly welcomed.


Booting multiple OS's

moral: pay attention during hardware upgrades.

Mon, 23 Dec 2002 18:06:41 -0500
Bob (x.generalx from verizon.net)

Your answer gang column in issue 85 had an article "Triple Booting" and had 1 segment of a triple boot as Windows 98.

Recently, I decided to upgrade my P3 MB to a P4 at 2.4gz. There was a combo of an Soyo P4vda MB and the P4 2.4gz that I couldn't resist. I did a lot of reading and the installed the MB. I also have a Slackware and Mandrake Linux installation.

On boot up, I got an error message from W98 that initialization of the NDIS had failed and the system had to be rebooted. It turned out that the only way it would boot from that point was in the safe mode. Needless to say, that's like being on a dead end street with no place to go. My 2 Linux installations were not accessible because the Promise card had been removed and they were now on hda and hdb and I couldn't get them to boot.

It seems that W95 & 98 at this speed of a P4 processor can only be made to work by getting a fix from Bill's os. Since my Pc was dead in the water, there was no way this could be done and the alternative was to install WXP. My true instincts said install Linux and to hell with windows.

Anyhow, its all said and done and WXP as far a I am concerned is a piece of crap. I sooner setup a graphics card in Slackware Linux than deal with what XP has to offer.

My reason for this litany of misery is to ward of some poor soul who might have the temptation to use this combo of a P4 2.4gz or higher processor with W95 or W98. You would think that somewhere there would be a flag to warn us but it was only after a call to Soyo, the MB manufacturer, that I learned of this pitfall. People tell us hard Linux is, if I had chosen this combo to install on Linux life would have been a bed or roses.

Bob Lee


answerguy and tag addresses gone

Wed, 4 Dec 2002 09:55:22 -0800
Mike Orr (Linux Gazette Editor)

The answerguy and tag addresses are now gone, "user unknown", bye bye, see ya. Answer Gang, expect a significant decrease in spam. -- Mike

And I suspect a significant amount of rejoicing from our sysadmin, Dan, who has to clean out the spamtrap occasionally... -- Heather


Thu, 12 Dec 2002 21:56:25 -0500
naylor (rnaylor from nhvt.net)

I found the back issues of the Gazette included in the Debian CDs. Another hidden gem. This alone was worth the purchase price. I enjoy the format of multiple answers to questions (eg: the answer gang) and I am suprised that other publications have not tried to copy the format. It kind of has the feel of being subscribed to a news list I subscribed to 'Linux Journal' a couple of years ago because of 'linux Gazette'.

I agree, Linux is more fun.

Why don't you advertise your magazine archives? ~ Buy Our Linux Gazette Archives And Get a FREE Debian 3 Disto.~

Heather specifically wanted The Answer Gang to read like an informal conversation, so that's how she edits it. I don't know why nobody else has copied the style. For LJ, it may be because of tradition and space. The Answer Gang takes up a lot of space when printed, and print magazines have only a limited number of pages, so you'd have to drop a couple articles. But people buy LJ for the articles. -- Mike

(curtsy) thanks for the compliment, guys. I figure, a thick enough thread feels a little like an installfest... all these clues flying around at high speed... bonking people occasionally, but all in good fun. -- Heather

As for the Debian CDs, those are handled by the Debian Project and the CD vendors, so it's their job to promote them. We do have LG on the Linux Journal Archive CD (store.linuxjournal.com, under "LJ Archives"). -- Mike

Re: virtual beer and feature request

Mon, 30 Dec 2002 16:57:24 -0800
Mike Orr (Linux Gazette Editor)
Request by Raj Shekhar (lunatech3007 from yahoo.com)

Can it be possible to append the author bio to the TWDT file. Or maybe make a TWDT for the author bio itself for each issue. I really enjoyed reading the bios :-).

We'll think about this. One of the purposes of the Author pages is to have the latest contact information and bio; the articles and TWDT would not be changed after publication.

Pehaps I can put the entire bio page (minus the links to previous articles, and minus the large type in the header) at the bottom of the TWDT article, with a note that this information may be old and another link to the Author page.

Thanks for looking into my feature request about the author's bio. What you suggested is exactly what I wanted.

Done, starting in January's issue. -- Mike

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Published in Issue 86 of Linux Gazette, January 2003

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