error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)'

I followed a lot of solutions online, but this is what finally worked.

This error occurs due to multiple installations of mysql. Run the command:

ps -A|grep mysql

Kill the process by using:

sudo pkill mysql

and then run command:

ps -A|grep mysqld

Also Kill this process by running:

sudo pkill mysqld

Now you are fully set just run the following commands:

service mysql restart
mysql -u root -p