= Booting LiveCD Without X =

LiveCD environments can usually be helpful for testing, but if you're troubleshooting a problem where X does not start up, that makes it difficult to retrieve the log files and other such things.  But it can be done:

0.  Obtain a Live CD for the release you're testing:  http://cdimage.ubuntu.com/releases/

1.  At the CD boot menu, add "text" to the boot options:  https://help.ubuntu.com/community/BootParameters

2.  The CD will now boot but not start X.

3.  You can grab xrandr data without starting an X session like this:

{{{
 xinit -e 'sh -c "xrandr --verbose > xrandr.txt" '
}}}

This will try to start X and log some information about the active screen resolution to the file xrandr.log before it stops X again.

4.  Start up an X session like this:

{{{
 startx
}}}

or

{{{
 /usr/X11R6/bin/X :0
}}}


= Bypassing/Disabling gdm =

== Option 0 - Automatic Login Through gdm ==
You can set up gdm to automatically log in a user either via {{{System > Administration > Login Window > Security > Enable Automatic Login}}}, or by editing the {{{/etc/gdm/gdm.conf}}} configuration file, and set  {{{AutomaticLoginEnable=true}}} and {{{AutomaticLogin=}}}<username>.  

== Option 1 - Turning off GDM after bootup ==

Switch to a tty (ctrl+alt+F1) or use ssh, log in, and shut off GDM for the current session like this:

{{{
   $ sudo /etc/init.d/gdm stop
}}}

Check to see if you have any remaining X sessions running, and if so, kill them:

{{{
   $ ps aux | grep /usr/bin/X
   bryce     5379  0.0  0.0   1784   552 pts/35   S+   03:10   0:00 grep /usr/bin/X
   root      7051  1.0  5.0 112224 105556 tty7    Ss+  Jul01 197:49 /usr/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp vt7

   $ sudo kill 7051
   $ sudo kill -KILL 7051
}}}
or just
{{{
   $ sudo pkill Xorg
   $ sudo pkill -KILL Xorg
}}}

This option is appropriate if your system boots up okay other than X, such that you can either ssh into it or access a tty.  If gdm is completely locking up your system during boot up, then see the next options.

== Option 2 - Temporarily disabling GDM ==

To disable gdm from running during boot, you can either boot with the "{{{text}}}" [[https://help.ubuntu.com/community/BootParameters|boot parameter]] or disable the rc service like this:

{{{
   sudo update-rc.d gdm stop 2 3 4 5 .
}}}

{i} Please note that there is a dot at the end. This is essential. 

Then to re-enable it later,

{{{
   sudo update-rc.d gdm start 30 2 3 4 5 . stop 01 0 1 6 .
}}}

This option is useful if gdm or X locks up the system during boot, or if you wish to run X in complete isolation from gdm.

== Option 3 - Removing GDM entirely ==

In order to disable X from starting when booting the system, you can
simply remove gdm from the init scripts:

  sudo update-rc.d -f gdm remove

and, to enable X again when booting:

  sudo update-rc.d gdm defaults

This option is probably only useful if you know you want to always boot X manually, and want to eliminate graphical booting entirely.

= Starting up X manually =

== Option 1:  startx script ==
From the text console, run 

{{{
startx
}}}

== Option 2:  Starting X directly ==
From the text console with no other X running, you can invoke X directly, bypassing all the startup scripts and stuff:

{{{
/usr/X11R6/bin/X :0 
}}}

If you're running multiple X sessions, use :1, :2 for second, third sessions.  (For debugging, it's usually easiest to stick with a single X session invoked from the console.)

X supports a wide variety of other startup flags that can be of value for debugging problems or working around issues.  See {{{man xorg}}} for a comprehensive list.  Here's a few particularly useful ones:

|| -allowMouseOpenFail || Allow the server to start up even if the mouse device can't be opened or initialised. ||
|| -ignoreABI || Bypasses server's ABI version check when loading e.g. binary drivers (-fglrx/-nvidia).  This option should be used with care. ||
|| -keeptty || Prevent  the server from detaching its initial controlling terminal.  This option is only useful when debugging the server.  Not all platforms support (or can use) this option.||
|| -showopts || For each driver module installed, print out the list of options and their argument types. ||