Mysql error while connecting to the Plesk panel on Linux server

[sven_sim]

While login to the Plesk Panel you may get the following error:

ERROR: PleskFatalException Unable to connect to database: mysql_connect() [<a = href='function.mysql-connect'>function.mysql-connect</a>= ]: Can't connect to local MySQL server through socket = '/var/lib/mysql/mysql.sock' (2) 0: common_func.php3:95 =09psaerror(string 'Unable to connect to database: mysql_connect() = [<a = href='function.mysql-connect'>function.mysql-connect</a>= ]: Can't connect to local MySQL server through socket = '/var/lib/mysql/mysql.sock' (2)') 1: auth.php3:124

Check the mysql service status on the server

mysqld dead but subsys locked

You see the mysql service is dead and hence cannot login to Plesk.
Try restarting the mysql service.

Now while restarting the mysql service you may get the following error:

-bash-3.2# /etc/init.d/mysqld start
chown: `mysql:mysql': invalid user
chown: `mysql:mysql': invalid user

Checking the mysql logs you get the error logs as below :-

-bash-3.2# tail /var/log/mysqld.log

110501 23:38:01 mysqld started
110501 23:38:01 [ERROR] Fatal error: Can't change to run as user 'mysql' ; Please check that the user exists!

110501 23:38:01 [ERROR] Aborting

110501 23:38:01 [Note] /usr/libexec/mysqld: Shutdown complete

As the error suggests the user 'mysql' does not exist.

Add the 'mysql' user

-bash-3.2# adduser mysql

Go to mysql directory.

-bash-3.2# cd /var/lib/mysql/

Check the ownerships

-bash-3.2# ls -la
-bash-3.2# drwx------ 2 27 27 4096 Nov 7 22:28 mysql

You see the ownership isn't right.

Assign the ownership recursively to the mysql user

-bash-3.2# chown mysql.mysql -R /var/lib/mysql

Then try to start the mysql service.

-bash-3.2# /etc/init.d/mysqld start

Timeout error occurred trying to start MySQL Daemon.
Starting MySQL: [FAILED]

Again the mysql service failed to restart..

Check the mysql logs once again.

-bash-3.2# tail /var/log/mysqld.log

110501 23:50:23 mysqld started
110501 23:50:23 InnoDB: Started; log sequence number 1 2821668223
110501 23:50:23 [ERROR] /usr/libexec/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 13)
110501 23:50:23 [ERROR] Can't start server: can't create PID file: Permission denied
110501 23:50:23 mysqld ended

Now you see there is different error coming up.

Check the ownership of /var/run/mysqld/

-bash-3.2# ls -ld /var/run/mysqld/
drwxr-xr-x 2 27 27 4096 May 1 21:49 /var/run/mysqld/

You notice that the ownership isn't right..
Correct the ownership of /var/run/mysqld/

-bash-3.2# chown mysql.mysql /var/run/mysqld/

Then try to restart the mysql service..

-bash-3.2# /etc/init.d/mysqld start
Starting MySQL: [ OK ]

and it's started just fine !

And now you can successfully login to the Plesk Panel.