problem with mysql

Hi,

I have a problem with mysql: when I want to restart mysql in WHM, got an erro message:
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usr/bin/mysqladmin: connect to server at 'localhost' failed error: 'Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)' Check that mysqld is running and that the socket: '/var/lib/mysql/mysql.sock' exists! mysql has failed, please contact the sysadmin (result was "Warning, no valid mysql.sock file found.mysql has failed").
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also, an error in .pid file:
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Fatal error: Can't change to run as user 'mysql'. Please check that the user exists!
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the user mysql is exists and have a right permissionson /var/lib/mysql ...

but now, when I run a command:
>> su mysql -c "/usr/sbin/mysqld"

mysql works fine only for 5 minutes ...


I did everything - mysqlup --force, upcp --force, create sock and pid filesmanually, changed my.cnf file, etc. but no results... Please help...