The root filesystem ran out of space, so I'm deleting all the extraneous junk.
I already deleted everything in /var/log and /var/cache/apt/archives and did sudo apt autoremove.
This /var/tmp is using 18.5 GiB. What is it used for? Is it safe to delete the contents?
UPDATE
I found these 2 swap files:
474M 10112015.tgz.swp
19G 10022015.tgz.swp
Those swap files were generated by opening tar files in vi.
Is there a way to limit the amount of storage space used by /var/tmp?