MSQLI errors after reboot, Centos panel won't start

Reboot server becuase running very slow.

After reboot I've got this:

Warning: mysqli_connect(): (HY000/2002): No such file or directory in /usr/local/cwpsrv/htdocs/resources/admin/include/functions.php on line 0

Warning: mysqli_connect(): (HY000/2002): No such file or directory in /usr/local/cwpsrv/htdocs/resources/admin/include/functions.php on line 0

Warning: mysqli_connect(): (HY000/2002): No such file or directory in /usr/local/cwpsrv/htdocs/admin/admin/index.php on line 0

Warning: mysqli_connect(): (HY000/2002): No such file or directory in /usr/local/cwpsrv/htdocs/admin/admin/index.php on line 0


Trying to start mysql server, please wait!
Try to restart CentOS Web Panel with command: sh /scripts/restart_cwpsrv

**Check your MySQL root password in: /usr/local/cwpsrv/htdocs/resources/admin/include/db_conn.php and /root/.my.cnf


Warning: mysqli_error() expects exactly 1 parameter, 0 given in /usr/local/cwpsrv/htdocs/admin/admin/index.php on line 0
Could not connect:

This is the 3rd time this has happened to us, other 2 times I re-installed. What is causing this? Any ideas please?

I noticed before reboot /dev/root was full. Partition size of 20GB.

I've tried restarting sh /scripts/restart_cwpsrv

Passwords are in the php and cnf files, I've even tried a password reset of mysql and passwords where updated.

you need to check that mysql is running and that root access connection also works, in some cases if mysql is slow it can be related to connection limits on mysql...but anyway you should test that.

The message claims about you check the passwords if are the same in both files "/usr/local/cwpsrv/htdocs/resources/admin/include/db_conn.php" and "/root/.my.cnf".
Impossible to know, but a partition full can cause impredictable problems in any case.
Are you already tryed create space in that partition..?