Database ERROR:Can't connect to local MySQL server through socket '/var/lib/mysql/mys

Please make sure that symbolic link for mysql.sock is not missing in /tmp partition.

Try this
---
stop mysql

run

# cd /tmp
# n -s /var/lib/mysql/mysql.sock mysql.sock

and start mysql service
---

 

This can be a number of things. Check the disk space to make sure it is not full, check the tmp directory contents and permissions, etc. You can also check the logs for any other possible clues.