====== Debugging X2Go Components ======

===== Log File Watching =====

If you want to track down problems with the server-side components of X2Go, it is possible to enable output of debug information into the systems syslog facility (normally ''/var/log/syslog'').

The default log levels for ''x2goserver'' and ''cups-x2go'' are set to ''notice''. Available log levels are: emerg, crit, alert, err, warning, notice, info, debug.

While testing e.g. your X2Go server, you can open another terminal on the server and watch the ''syslog'' file:

<code>
root@x2goserver:~$ tail -f /var/log/syslog | grep x2go
</code>

Other logging locations apart from the system's log are:

  * X2Go Server: ''/var/log/syslog''
  * X2Go Client: stderr (use ''%%--debug%%'')
  * PyHoca-GUI: stderr (use ''%%--libdebug --debug%%'')
  * Xsession itself: ''$HOME/.xsession-x2go-errors''
  * NX (server-side): ''$HOME/.x2go/C-<sessionid>/session.*''
  * NX (client-side): ''$HOME/.x2go/S-<sessionid>/session.*''

===== Enable Debug Output =====

==== Debugging X2Go Server ====

The ''x2goserver'' log level can be set by editing:

<file>
root@x2goserver:~$ editor /etc/x2go/x2goserver.conf
</file>

==== Debugging cups-x2go ====

For debugging cups-x2go there are two files to look at:

  * ''/var/log/cups/error_log'' - in case ''cups-x2go'' code has a bug (e.g. a syntax error) or fails otherhow
  * ''/var/log/syslog'' - in case anything goes wrong while ''cups-x2go'' is processing a print job

For setting the log level of your CUPS server, please investigate the ''cupsd.conf'' man page: 

<code>
$ man cupsd.conf
</code>

The ''cups-x2go'' log level can be set by editing:

<file>
root@printserver:~$ editor /etc/cups/cups-x2go
</file>

==== Debugging X2Go Session Broker ====

The ''x2gobroker'' debug mode can be enabled in:

<file>
root@broker:~$ editor /etc/default/python-x2gobroker
</file>

The log files normally get written to ''/var/log/x2gobroker/*.log''

You can also run 
<file>
root@broker:~$ x2gobroker-daemon-debug
</file>

as user ''root''. This is equivalent to running the broker daemon provided by the package ''x2gobroker-daemon'', but you will see all output piped to stderr while the X2Go Session Broker daemon runs in foreground mode.
==== Python X2Go / PyHoca Debugging ====

The PyHoca clients both have a ''%%--libdebug%%'' option. Run ''pyhoca-gui'' or ''pyhoca-cli'' from the command line with that option enabled and you get blasted with debug output.

===== Customizing Debug Messages =====

All X2go server scripts are ready for syslogging, though not all of them actually do log to syslog. If you want to add your own syslog messages for debugging purposes, please take a look at the code of files that already do report to syslog.\

Here is a little howto that explains how to add extra log output to X2go server scripts:

==== Logging in X2Go Server's Perl Scripts ====

Whereever you want to write a line to syslog from an X2Go Server's Perl script, place this command:

<code>
syslog('debug', '<My message to syslog...>');
</code>


==== Logging in X2Go Server's Shell/Bash Scripts ====

Whereever you want to write a line to syslog from an X2Go Shell/Bash script, place this command:

<code>
$X2GO_LIB_PATH/x2gosyslog "$0" "debug" "<My message to syslog...>"
</code>


==== Logging in X2Go Session Broker's Python Module ====

Whereever you want to write a line to ''/var/log/x2gobroker/broker.log'' from one of the python-x2gobroker module files, place this command:

<code>
# at the top of the module file:
from x2gobroker.loggers import logger_broker
# [...] then further below, wherever needed:
logger_broker.debug('<your message>')
</code>


==== Debugging x2goclient on Windows ====

This is a bit tricky. You need to run the debug version of x2goclient in a cmd window. The debug version is part of the xgoclient installation package for Windows and is called ''x2goclient.debug.exe''. If it is not available on you machine re-run the installer.

Run ''<path_to_your_installation>\x2goclient --debug --libssh-debug --libssh-packetlog 2>logfile.txt'' (+ further options you might require) and run your session as usual. The session log file ''logfile.txt'' will be created in the current directory and can be opened e.g. with notepad.

Run ''x2goclient --help'' for available options.

<note important>important The options are always prefixed by two ''-'', your browser might display them as one!</note>