I have run into this issue a few times now, which is very much a pain to deal with.
Here I am, going along with my server, everything going ok, and then suddenly, I can’t upload any images to a sites. Weird error. Ok, lets reboot the server, maybe it’s a minor glitch.
Nope, now the MySQL server wont even start!
sudo service mysql start
start: Job failed to start
Of course, this is after I did the query:
sudo service mysql status
[yes, this is also very similar to the problem I was having earlier with user privileges]
After fooling around for a while, trying to figure out what was going on, nothing would work. I noticed that I had a few packages that needed updating/upgrading. So, I ran:
sudo apt-get update
sudo apt-get upgrade
When in the upgrade process, I noticed that the MySQL updates gave me an error, but the error made reference to something related to space.
Looking at my capacity, and remembering that I had just uploaded a large *.zip file (a few houndred Mb).
Deleting some documents (some large document) I was able to then get MySQL to start and make me a happy admin!
Hope this helps!