Request for explanation of error message

[Paul Smith]

On Mon, 2019-07-29 at 04:14 +0800, Bret Busby wrote:
> > The first one is simple enough.  It might have been because your disk
> > is full, in which case it's a symptom not a cause.  What are the
> > permissions on these files?  Run this command:
> > 
> >    ls -ald /tmp /tmp/.tX0-lock
> > 
> > and let us know the results. 
> 
> "
> bret at bret-MD34045-2521:~$ ls -ald /tmp /tmp/.tX0-lock
> ls: cannot access '/tmp/.tX0-lock': No such file or directory
> drwxrwxrwt 19 root root 4096 Jul 29 03:57 /tmp

This looks correct.  That most likely means that this error is a
symptom of your disk being full, and not the cause of the problem.

After you have cleared out space on your disk, please keep an eye on
the size of the /var/log/lightdm/x-0.log file.  If it continues to
grow, send along the last 50 or so lines of output from that file and
we'll see what it has to say.

Also, you did show you're using an 18.04.2 based system, but if you're
using lightdm it won't be out-of-the-box vanilla Ubuntu.  I didn't see
the output of the "lsb_release -a" command which would tell us (I
think) if you're using a spin or similar.

What distribution did you actually install here?