Frequently asked questions - Linux

• 1. After 2024-10-01 my ssh login to merlin stopped to work (or some service like SVN, GIT etc.)

  There was a change in server's SSH key. It is necessary to delete the entry in your ~/.ssh/known_hosts, then you can check again (with request for confirmation) with ssh login@merlin

• 2. How to access servers aja and fik from Linux?

  /usr/local/samba/bin/smbclient -U FIT/login \\\\aja\\fit
  

• 3. How to clean up SQLite databases for FireFox?

  In the directory of your Firefox profile enter:

  for i in *.sqlite; do echo 'VACUUM;' | sqlite3 $i; done
  

• 4. How to switch czech and english keyboard?

  In text console with key Pause, in graphic system with key ScrollLock or via setting of your desktop manager - in KDE you can set this in "Control Center"

• 5. Soundcard is not working, can not hear anything...

  Check your mixer settings with alsamixer. Soundcards could be muted or volume level can be very low. Withing alsamixer you can use cursor keys, with key M use control mute/unmute.

• 6. How to burn DVD+-R či DVD+-RW?

  For burning of DVDs you can use tools from dvd+rw-tools:

  • dvd+rw-mediainfo - info about inserted medium, max. speed of burning etc.
  • dvd+rw-format - formating of some new DVD+-RW media. Most of the time, you do not need this and you can burn your data immediately. ručně.
  • growisofs - burn image or data. No need to clean medium before, parameter -Z causes previous content to be erased, with -M you save the content and add new data at the end. Details in man growisofs

• 7. Can not compile program in C++, there are several screens of errors!

  It may be necessary to use some older version of GCC with different support for you C++ standard. Available versions can be listed with: ls /usr/local/bin/gcc-*. Example:

          g++-4.6 -o SN_devel SortNets.cc -lcurses /usr/local/lib/libstdc++.so.5
  

• 8. In my terminal, the prompt is not initializes and other settings does not work properly.

  Some terminals do not source ~/.profile for every tab/window, you can solve this by ln -s ~/.profile ~/.bashrc. This can caouse some troubles, like for login via ssh remotely etc.

• 9. How to use Subversion/GIT repositories?

  Subversion/GIT server are prepared on merlin.fit.vutbr.cz. You can have your own repo, but because of shared $HOME via NFS and troubles with locking, it may be better to ask for official /svn or /git repository. Request including name for the repo, name of the project the repo is for and list of login names for access can be sent to linux@fit.vutbr.cz or via this form

• 10. Can not run programs on merlin any more - error fork: Resource temporarily unavailable

  On merlin server there is a limit on number of processes per student. This is mainly because running test project can fork tons of processess that are not cleaned up properly. If you can, clean up your processes, usefull commands are: ps awxu | grep $USER and kill -9 PID or killall -9 PROCESS_NAME. If you are not able to run any process, you have to ask for help on linux@fit.vutbr.cz

• 11. After wiki page edit I got error: The action you have requested is limited to users in the group: Users.

  After upgrade to newer version of mediawiki, there is a change in user profiles. It is necessary to enter you user my preferencies link and here in right menu use Restore all default settings and finish with Save.

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Any comments to this page should be sent to kasparek@fit.vutbr.cz