Check the folowing

1. First check if another instance is runnig in the same machine

   ps ax | grep mysql

2. Then, check if your file my.cnf (probably in /etc/mysql/ folder) is correctly configured with

[mysqld]
datadir = /var/lib/mysql/
socket = /var/lib/mysql/mysql.sock

3. Next, you have changed the default data directory, did you gave the right permissions to the new directory now

 chown mysql:mysql -R /var/lib/mysql/*
 chmod 755 -R /var/lib/mysql/*

4. After changing the permission restart the service and check

   service mysql restart

It would appear that the socket file is missing. service mysql stop and service mysql restart depend on the socket file's existence to shutdown.

You will have to connect to mysql using mysqladmin and TCP/IP to shutdown

MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-h127.0.0.1 -u${MYSQL_USER} -p${MYSQL_PASS} --protocol=tcp -P3306"
mysqladmin ${MYSQL_CONN} shutdown
service mysql start

I have posts about shutdowns like this

My issue was that multiple mysql processes were running concurrently.

First kill the processes with:

sudo pkill mysql

and

sudo pkill mysqld

restart mysql

sudo service mysql restart

now you should be able to log in

mysql -u root -p

Hi i'have just installed zabbix 3.0 and same problem appeared after few hours ago. When i check the zabbix permission in the phpmyadmin I realised there is no permission for user "zabbix" . I gave Grand permission to zabbix and problem solved. This might be helpfull for someone.

I was getting the same error as well "ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib /mysql/mysql.sock' (111)". I have uninstalled and re-installed MySQl several times and have spent multiple hours troubleshooting the issue. The issue that I notice is when I added the credentials in the my.cnf option file located in /etc/my.cnf as this will cause MySQL issues with starting the services and would throw the error.

To resolve this, I removed the credentials out of the my.cnf option file in /etc/my.cnf and I create a .my.cnf option file in the home directory. For example /home/username/.my.cnf in Linux (replace username with your username in Linux) and add the credentials in there. No issues after that.

I got the same error, but simple reason: system had run out all disk space.

Check your mysql service or if you are accessing through ssh try running:

sudo /etc/init.d/mysql start