Root partition full and can't account for all 4GB

mdgm wrote:
Oops the service may be called mysql # systemctl restart mysql Why have you got one or more large MySQL databases stored on the OS partition?

Ran the restart, I should have realised that it was mysql. Still at 93% used now.
Not sure what the db is doing there. Here's the list of them below. But all this still is accountable for in terms of the space. I can't account for all the space being used to try and free up any more space.

root@RIGHTSTER-NAS:/var/lib/mysql# ls -l
total 741380
-rw-r--r-- 1 root  root          0 Dec 20  2013 debian-5.5.flag
-rw-rw---- 1 mysql mysql 748683264 Dec  4 10:41 ibdata1
-rw-rw---- 1 mysql mysql   5242880 Dec  4 10:41 ib_logfile0
-rw-rw---- 1 mysql mysql   5242880 Dec  4 10:41 ib_logfile1
drwx------ 1 mysql root       2094 Dec 20  2013 mysql
-rw------- 1 root  root          6 Dec 20  2013 mysql_upgrade_info
drwx------ 1 mysql mysql       868 Dec 20  2013 performance_schema
drwx------ 1 mysql mysql        96 Dec 20  2013 Syslog
drwx------ 1 mysql root          0 Dec 20  2013 test