After having many troubles with the ‘Xauthorization file’ in Ubuntu (8.10) today, I thought I’d share the simple solution to the problem that took me at least an hour to solve. No guarantees, though!

The Problem

When trying to execute administrative tasks (such as installing updates and running Synaptic Package Manager) you receive a ‘Cannot copy the user’s Xauthorization file’ error.

The Diagnosis

After extensive research, I realized that the problem did not lie with an incorrect xauhorization file in my home directory. The problem instead lies with your /tmp directory being full.

To check if this is also the case in your environment, open a terminal (Accessories->Terminal) and type:

df -k

This will output the status of the various areas of your Ubuntu environment. Check if ‘/tmp’ has a ‘100%’ reading the ‘Use%’ column. If so, then you can use this solution to fix your problems.

The Solution

Clear your /tmp directory by deleting its contents through the file manager (Nautilus). You can skip the files that can’t be deleted. Log out and in again to ensure that everything’s OK. Everything should work now.

PS. If you (like me) ran Firefox with ’sudo’ to be able to access the internet (to get information on the problem), you might experience problems with Firefox in the normal (non-sudo) mode afterwards. Read this post for help with this problem: http://ubuntuforums.org/showthread.php?t=801136.