Symptoms
When accessing cPanel >> MySQL Databases you receive the following error:
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 error log here:
/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
If you observe this 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.
It 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: Make sure to replace $user with the affected cPanel account's username.
You can find more documentation about this tool here: The rebuild_dbmap script.