Yesterday my server CentOS was turned off 2 times, because of electricity problem an NagiosXI was interrupted too. I cannot run http://myIP/nagiosxi

The problem is Mysql service cannot restart.

Th Solution 


To prevent the problem from occurring, you must perform a graceful shutdown of the server from the command line rather than powering off the server.
# shutdown -h now
 
Note : The above command will shutdown your CentOS and you need to click power on to turn on the machine.  If your server is not near by your hand, should not use this command.

This will stop the running services before powering down the machine.

Based on Centos, an additional method for getting it back up again when you run into this problem is to move mysql.sock:
# mv /var/lib/mysql/mysql.sock /var/lib/mysql/mysql.sock.bak

# service mysqld start
 
Restarting the service creates a new entry called mqsql.sock