Ubuntu – MySQL running but not responding

Try to add skip-name-resolve to [mysqld] section of /etc/my.cnf like this:

[mysqld]
skip-name-resolve

Seems to be a name resolving issue.

1. No, but check logs for warnings and errors. You may need to issue a REPAIR in certain circumstances.
2. No, if you need to a file system check, it will prompt you to do one, or run one automatically. the Linux equivalent is an fsck (filesystem check). How this works completely depends on the filesystem you're using.
3. OPTIMIZE table can clean up unused space (i.e. if a lot of data was changed or deleted). Depending on your schema and data usage it may or may not be useful. Again, be careful when you run this, MySQL locks the table during it running.

Althuogh these are fine questions you're asking, the real root cause of this was a filesystem filling up. That is the problem you need to solve:

1. If the primary function of this machine is a database server, the MySQL database should be on it's own partition. If it's just a secondary function, at the very least make sure /var is off on it's own partition (or the base directory of whereever your MySQL data directory is). You should not be able to crash MySQL by adding files to /home or /

2. You should be alerted to filesystems that get far too close to being full. Nagios or hyperic can do this for you and a whole host of other sanity checks and warnings that can alert you to potential dangers.