I have an ancient web application that a few people still rely on. A year or so ago I discovered that the database that backs it had filled almost all of the disk space available. I deleted a lot of the no longer needed content from the database and that was when I learnt that MySQL doesn't deallocate disk space.
I was able to free up about 14Mb which was enough for Apache to write its log files.
It has limped along since and the users that have been using it have stubbornly continued to despite my gentle suggestion that they use the new thing I built that works a bit better!
Today something has eaten the magic 14Mb and everything has stopped working.
Is there anything I can do to reclaim some of the space from MySQL without killing all the data in it?
UPDATED with some of the details asked for in comments:
du -hs /var/lib/mysql
: 30G
df -h
: size 36G, used 34G, avail 0, use 100%
SHOW VARIABLES LIKE 'version'
: 5.5.28-0ubuntu0.12.04.3