Comment 78 for bug 379157

With a LiveCD you lose all changes when you reboot, but you don't need to reboot to activate the changes[*]. It is sufficient to restart X, and you can do that by simply logging out (on a LiveCD you will be logged in again after 10 seconds IIRC). Alternatively, you can switch to a VT and do a `/etc/init.d/gdm restart`.

The easiest way to get the log files when your computer has a black screen is to ssh in from another computer. For that you need the computer to be connected via cable instead of wireless and you will need to `apt-get install openssh-server` and since it is a LiveCD you will need to set a password for the ubuntu user to be able to log in with `passwd`, or alternatively for the root user with `sudo passwd root`.

If you don't have another computer available to ssh from, you can also save the Xorg.0.log to a USB key. Before you restart X, insert the USB key and see where it gets mounted (should be /media/something). Then from a VT before you restart X, write `sleep 60; cp /var/log/Xorg.0.log /media/something` where you replace something with the appropriate directory. That should wait 60 seconds and copy the log file. If you restart X during those 60 seconds, a new Xorg.0.log will be created and despite your black screen you will get the log file on your USB stick.

[*] I remember you had some problems earlier that mysteriously went away when rebooting, but hopefully those won't show up now.