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Linux FAQ

This is my very personal Linux FAQ (well, actually Once-Answered-Questions,
but FAQ ist a more common term). As it is found by Google, it my help you.
Please no flames for not beeing beginners-friendly. This is a list from an
expert to experts focused on the very core of the problems.
 (Myself, I am getting embaressed about solutions to problems that describe
how to use a configuration GUI while the problem is just to pick the right
driver module or give the right parameters)
 Any feedback is highly welcome, please write to

            "Peter J. Weyers" <linux-faq(a)usr-local.org>.

Further questions (even beginners ;-) ) might be answered too!

Q: Why do I get sometimes the error "Session management error: Could not open network socket" when running some X11 applications within screen? A: Gnome stores the socketname of the session manager in the environment variable "SESSION_MANAGER". If you reuse you re-attach your screen session after restarting gnome, this setting is out-of-date
Q: I have a binary, that can be seen with file and ls, but when starting it or trying to analyze the problem with ldd, I get an "No such file or directory " error: (root) ~ # which me /usr/local/bin/me (root) ~ # ll /usr/local/bin/me -rwxr-xr-x 1 peter users 115096 Feb 2 13:39 /usr/local/bin/me* (root) ~ # /usr/local/bin/me zsh: no such file or directory: /usr/local/bin/me (root) ~ # ldd /usr/local/bin/me /usr/bin/ldd: /usr/local/bin/me: No such file or directory A: Very strange indeed. I had this once and it was resolved by installing ldso (old dynamic linker) and libc5
Q: Adobe Reader as well as its Mozilla plugin start with the error message "There was an error while loading the plug-in 'PPKLite.api'. The plug-in failed to initialize." A: Follow the Readme: symlink libldap.so.X and libber.so.X to libldap.so and libber.so respectivly into the directory <Installation Directory>/Reader/intellinux/lib
Q: Sometime XMMS hangs forever ... A: There's been a discussion on futex_wait problems with xmms on the kernel mailing list. You can check wether you have such kind of problem by attaching strace to the hanging xmms process: strace -p <pid of xmms> I havn't enough experience with it yet, but maybe the following way of starting XMMS is a workaround: LD_ASSUME_KERNEL=2.4.19 xmms
Q: How can I find out the environment settings of a running process? A: Do a cat /proc/<PID of process>/environ|xargs -0 -n 1 echo
Q: Strange characters of filenames in GTK, GTK2 or GNOME applications ... A: Try setting G_FILENAME_ENCODING to @locale
Q: Since upgrading to Kernel, fuse seems not to work any more ... A: Check the documentation on Documentation/Changes in your kernels source tree as it is written in the kernel config's help screen: Needs libfuse 2.4.0 or later. Absolute minimum is 2.3.0 but mount options 'direct_io' and 'kernel_cache' won't work.
Q: After upgrading to kernel, starting XFree86 with NVIDIA driver and using Synaptics driver for the core pointer fails. A: For me, the following worked: 1. Use /dev/input/mouse0 in core pointer section 2. Make sure hotplug is stopped (propably the point is to unload usbhid) 3. Load event device module (modprobe evdev) 4. Load PS/2 mouse driver module (modprobe psmouse) 5. Start hotplug 6. Start XFree86
Q: After enabling exif rotatin in gimageview (gimv) 0.2.27 it crashes now and then ... A: The following patch seems to mitigate the problem to a gtk error: --- src/gimv_image_view.c.orig 2006-10-09 18:55:31.000000000 +0200 +++ src/gimv_image_view.c 2006-10-09 19:02:03.000000000 +0200 @@ -1824,7 +1824,7 @@ ExifByteOrder byte_order; ExifShort v_short; - g_return_val_if_fail (info->filename && *(info->filename), 0); + g_return_val_if_fail ( (int)info && info->filename && *(info->filename), 0); jdata = jpeg_data_new_from_file (info->filename); if (!jdata) { Ah, ... well. Yes, you have to get the sources and recompile. Sorry, dude.
Q: X11 selction does not work as I am used to ... A: You do not have - by any chance - weird (i.e. dead, double) instances of x2x running?
Q: How do I turn on disk quota on a debian systems with only quota version 1 enabled? A: Do as root: aptitude install quotatool quotacheck -M -g -F vfsold / quotacheck -M -u -F vfsold / /etc/init.d/quota start to set e.g. group quotas to 2800 MB with a hard limit of 3000 MB for group "users" do: quotatool -g users -b -l 3000M -q 2800M -v / and check with quota -g users
Q: After upgrading to exim3 I get a lot of "failed to open DB file /var/spool/exim/db/retry: File exists" errors in my exim cron jobs. A: Run db3_upgrade /var/spool/exim/db/retry db3_upgrade /var/spool/exim/db/wait-remote_smtp_smarthost as root.
Q: How do I remove the passphrase from a RSA key with openssl? A: Try openssl rsa -in rsa-key.pem -out rsa-key-insecure.pem
Q: I am using "noresume2" at the kernel command line, but the booting kernel throws warnings about suspend2 nevertheless ... A: Using "resume2=off" worked for me ...
Q: After upgrading from nfs-user-server to nfs-kernel-server mounted directories do not show up in the exported filesystem tree any more ... A: Do an extra entry for each local mounted filesystem in /etc/exports and give them the "nohide" option.
Q: How do I get the mapping of USB devices to device nodes (like /dev/input/mouse0 or /dev/sdb) if I don't want to use udev? A: In general, if you have udev installed, the scripts below /etc/udev/scripts might give you some hints. E.g. for /dev/input, have a look into /proc/bus/input/devices, for usb-storage devices, the symlink /sys/block/sdb/device/ is very promising