I logged on to my computer on Monday this week and ran
startx as usual, but Xserver crashed, complaining that it couldn't write to
/tmp. At first I thought there was an odd permissions issue or some problem with
.Xinitrc, but it turns out after running some exploratory
du -h commands that my root partition was completely full.
The culprit turned out to be the file
/var/log/uvcdynctrl-udev.log, which had ballooned to 20GB in size. The culprit is libwebcam. This is a well-attested problem which apparently still doesn't have a solution:
I didn't have time to work out how to solve it properly, so I set up a simple-as-it-gets crontab:
0 12 * * 1 rm /var/log/uvcdynctrl-udev.log
No dramas so far!