Request for explanation of error message

[Paul Smith]

On Mon, 2019-07-29 at 02:51 +0800, Bret Busby wrote:
> Whatever is happeing, I now have
> 
> "
> bret at bret-MD34045-2521:~$ ls -l /var/log/lightdm/x*.*
> -rw------- 1 root root 64086904832 Jul 29 02:49 /var/log/lightdm/x-0.log
> "
> 
> and no space left on the / partition.
> 
> So, whatever is happening, the file, as it stands, has to be deleted,
> as it has rendered the system unusable.

I haven't been following this thread, but I mean, have you looked at
the contents of that file to see what it says?

You can view the last 20 lines, for example, by opening a terminal
window and running:

  tail -n20 /var/log/lightdm/x-0.log

It could be that it's spewing errors or warnings to that file, which
could lead you to a poorly-behaving program on your system or warn you
about some hardware or configuration issue.

I don't use lightdm (I use standard gdm) so I can't say for sure but
it's possible simply deleting that file won't solve your disk space
problem: if lightdm keeps the file open to write to it then removing it
via "sudo rm -f /var/log/lightdm/x-0.log" won't actually free the disk
space: on POSIX systems disk space is only cleaned up when there are no
more references to the file.  If you try to delete it and you're still
out of space you'll have to at least log out and log back in to restart
the display manager, and/or possibly kill the process.

In general those log files are for your information, for helping to
track down issues.  The system itself doesn't need them for proper
operation so if you need to delete them you should feel free to do so. 
It won't break anything.