Error : The adminbin “cpmysql” in the “Cpanel” namespace call to function “DBCACHE” ended prematurely: The subprocess reported the “” (255) error when it ended

This error was there in user’s cpanel section and no database, no db users etc were showing in the cpanel for the users.

On checking the /varlib/mysql/server.domain.com.err (mysql error log) I can see the mysql user table was corrupted and needed repair

141204 12:13:56 [ERROR] /usr/sbin/mysqld: Table ‘./mysql/user’ is marked as crashed and should be repaired

You can repair mysql database via command line

# mysqlcheck -r mysql

================
mysql.user
warning : Number of rows changed from 282 to 283
status : OK
================

You can see table mysql.user is crashed and after repairing the issue will get fixed.