Q:

Is safe to remove the files name off.xxx in /var/lib/mysql/?

Today, my HDD is full usage with the folder /var/lib/mysql/.
There are the hundreds of files with name off.000001, off.000002,... off.000190 and one file with name off.index.
What do they mean and can I remove all of them?

A:

this is either your binary log or your relay log.... if you do not have a master/slave setup, comment out all "bin-log" and "relay-log" entries in /etc/my.cnf, restart mysql, and delete all those files.
if you do have a master/slave setup, i believe you there is an "expire-log" directive now, or you can just cron "find /var/lib/mysql -name "off.*" -mtime +3 -delete" or something like that.

