Symptoms
When accessing cPanel >> MySQL Databases you receive an error with the following:
The MySQL server is currently offline.
adminbin Cpanel/cpmysql/DBCACHE: exit 255"
Description
Whenever there is an issue with the cPanel interface, the most helpful thing you can do is check the cPanel logs at the following file:
/usr/local/cpanel/logs/error_log
Checking that error log file will likely give you more details on the problem, and that may even be enough to resolve the issue.
Workaround
In this case, I found the following entry in the cPanel error log while loading the cPanel >> MySQL Databases page:
Cpanel::Exception::Database::CpuserNotInMap/(XID xfttxq) The cPanel user “username” does not exist in the database map.
When this happens that indicates there is an issue with the MySQL system, but fortunately there is a cPanel tool to get this taken care of. You can run the following command to update the user's database map on the machine:
/scripts/rebuild_dbmap $user
and that will get things working properly.
NOTE: You will want to be sure to replace $user with the affect cPanel account's username.