Debugging printing – CUPS

Some time ago I noticed that printing works somewhat strange on my desktop. It ran smoothly in most of the cases, but rarely it refuse to produce output. The really weird thing is that I didn’t know why it behaved in such a strange manner. As it is stated Murphy’s laws, it seem to fail when I was in a time-pressure situations. “Luckily”, One day, when my printer produced an error instead of doing its job, I had a time to solve the problem.

Analysis – user part

First of all, I needed to work out what is the real problem. I tried printing a few different documents. I selected those problematic and checked whether they are printable with other programs or configuration. The basic rules are:

1. Repeatability and reproducibility – in what kind of situation does problem occur? Am I able to reproduce errors within doing the same steps? Does the problem repeat while using certain applications or it is document/configuration specific?
2. Isolation – what kind of programs are involved? Pinpoint all of the programs and configuration files that could cause the problem.

My answers to this questions:

1. Repeatability and reproducibility – the problem seems to be document specific. I found that it occur only within a small number of PDF and ps files.
2. Isolation – printing program related to CUPS such as ghostscript, pnm2ppa, foomatic and CUPS itself.

Analysis – debugging

At first I looked up for logs (“/var/log/cups/error_log”). It wasn’t useful at all, however It suggested turning on the debugging mode. So I look into CUPS config (“/etc/cups/cupsd.conf”) and changed LogLevel to debug.
[code lang="bash"]
#LogLevel info
LogLevel debug
[/code]
I tried printing one of those baffling documents. I looked at errors and saw:
[code lang="bash"]
(...)
D [17/Apr/2007:22:15:56 +0200] [Job 151] GPL Ghostscript 8.54 (2006-05-17)
D [17/Apr/2007:22:15:56 +0200] [Job 151] Copyright (C) 2006 artofcode LLC, Benicia, CA. All rights reserved.
D [17/Apr/2007:22:15:56 +0200] [Job 151] This software comes with NO WARRANTY: see the file PUBLIC for details.
D [17/Apr/2007:22:15:56 +0200] [Job 151]
D [17/Apr/2007:22:15:56 +0200] [Job 151] Closing renderer
D [17/Apr/2007:22:15:56 +0200] [Job 151] Error: /VMerror in --stringwidth--
(...)
[/code]
So it is definitely a ghostscript error. I googled VMerror and found that it is a postscript error which means that my RIP (ghostscript in this case) doesn’t have enough memory. Because I have a lot of free RAM, it is probably a bug of ghostcript.

Solution

I simple searched for ghostscript alternatives in the portrage(“eix ghostscript”). I decided to switch from “ghostscript-GPL” to “ghostscript-esp” so I entered:
[code lang="bash"]
emerge --unmerge app-text/ghostscript-GPL
emerge app-text/ghostscript-esp
/etc/init.d/cups restart # restarting cups service
[/code]
After these steps printing services work properly.

Strange error

I encountered a strange error while I was using subversion. I was checking out some of the programs sources while I got a message:

[code]
Fetching external item into 'koffice/kdgantt'
svn: PROPFIND request failed on '/home/kde/trunk/KDE/kdepim/kdgantt'
svn: PROPFIND of '/home/kde/trunk/KDE/kdepim/kdgantt': SSL negotiation failed: SSL disabled due to library version mismatch (https://svn.kde.org)
[/code]

As I had correctly installed subversion and openssl, I guessed that the linkage is the problem. That kind of problems should be removed by running revdep-rebuild. This time revdep didn’t help, so I re-emerge both programs manually. After that, svn worked as usual. The strange behaviour seems to be an issue of portrage’s ebuild.

Fixing KDE paths after doing an emerge

I’ve decided to upgrade my Gentoo OS. I hadn’t done it before, because I’m using computer on a daily basis and I don’t want have computer frozen for about a day just to have KDE 3.5.5 instead of KDE 3.5.2. So I have to download and compile more than 1.3GB. It is too much for my computer to do it in a single shoot. So I decided to upgrade it within few steps (e.g. one night for X, …). Each evening, I used command (xyz is a package like xorg-server):

[code lang="bash"]
emerge -uN deep xyz; poweroff
[/code]

After one of that nights my kdm doesn’t appear after booting. Instead of it I saw an ugly xdm. Quick lookup to display 1 (Ctrl+Alt+F1) show an error:

[code]
which: no kdm in (/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/3.4.6:/opt/sun-jdk-1.4.2.12/bin:/opt/sun-jdk-1.4.2.12/jre/bin:/opt/sun-jdk-1.4.2.12/jre/javaws:/usr/qt/3/bin:/usr/games/bin)
[/code]

As I noticed there was no KDE paths in it. I guessed correctly that something with /etc/env.d/* has happened. I found on net that there should exist two files related to KDE in this directory:

• 45kdepaths-3.5
• 99kde-env

In my file system a file /etc/env.d/*kdepaths* didn’t exist. So I created it.

Content of “/etc/env.d/45kdepaths-3.5″:
[code]
PATH=/usr/kde/3.5/bin
ROOTPATH=/usr/kde/3.5/sbin:/usr/kde/3.5/bin
LDPATH=/usr/kde/3.5/lib
CONFIG_PROTECT="/usr/kde/3.5/share/config /usr/kde/3.5/env /usr/kde/3.5/shutdown"
[/code]

Than I ran:
[code]
env-update
[/code]

And after that everything work as usual.

Setting up internet sharing over bluetooth

Today, I decided to set up internet sharing from workstation to my PPC. As my desktop PC and PDA have bluetooth, I wanted to use it instead of inconvenient USB cable.

Firstly, I look through Gentoo Linux documentation. I found two interesting articles, about bluetooth¹ and routing². I follow them, which mean I rebuilt kernel, emerge a few programs and play for a while with configuration. From PPC side, I simple switch to static addresses and enter them. Everything worked as expected, till I decided to restart my computer. After that, I realised that bluetooth interface (bnep) didn’t have proper IP. The reason of that mistake was that script “/etc/bluetooth/pan/dev-up” hadn’t been execute. I double-checked permissions and name of that file, but it didn’t help. Documentation³ didn’t give me any clue. After some web searching, I noticed people who have the same problem, but unfortunately, I didn’t find solution.

At that moment, I decided to use some messy scripts to do that job. However, I still wondering, why my first method doesn’t work. I hope to figure it out.

1. Gentoo Linux Bluetooth Guide [back]
2. Home Router Guide [back]
3. HOWTO PAN [back]