mysql service offline - mysql.sock location

Question

Our mysql service went offline earlier and when we attempted to restart it we were presented with the following error:

System error 2: No such file or directory ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

We checked the mysql config and it is looking in: datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock

but our mysql.sock file is no longer present in /var/lib/mysql/

We tried 'whereis mysql.sock' and it returned: mysql: /usr/bin/mysql /usr/lib/mysql /usr/share/mysql /usr/share/man/man1/mysql.1.gz

Several help guides suggested running: ln -s /var/lib/mysql/mysql.sock /tmp/mysql.sock

but /temp/ is empty.

Does anyone know how we might repair this problem please?

Answer 1

The socket is a temporary file which is created when the service starts up, similer to a tcp or udp port, please check your mysql log to see why mysql is not starting.

Answer 2

Try touch /var/lib/mysql/mysql.sock

It may go ahead and setup the socket as long as the file exists. You might make ownership the mysql user as well.

The location must be writeable and readable my the mysql user. (Your mysql user may be different I think the default is mysql)

chown -R mysql /var/lib/mysql/

A rough mini-tut is here: http://anthologyoi.com/computers/cant-connect-to-local-mysql-server-through-socketerror.html

In addition if the mysqld perocess is running you might want to kill any instances and then try restarting. pidof mysqld should tell you if any instances exist.

Also instead of whereis the command find / -name mysql.sock may be more helpful.

Answer 3

If it's refusing to start, it might need reinstalling to get the files back.
cp -a /var/lib/mysql /root/mysql_backup
for i in $(rpm -qa | grep "mysql"); do echo "Erasing $i"; echo "$i" >> /root/erased_rpms; rpm -e $i; done (the erased_rpms is just in case this has done too much afterwards)
yum install mysql-server