MySQL Daemon Lock issue

I experienced the same issue today on my Ubuntu server. But I think the solution is NOT to disable locking. In my case, a look at the system log (dmesg | tail and journalctl -xe) revealed that it's an apparmor issue and the solution can be found in this question.

I had following error

[ERROR] Unix socket lock file is empty /var/lib/mysql/mysql.sock.lock.

This error came up as a result that my server was lacking space 100% use (see below)

Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/xvda1      41153856 28531384  12187364  100% /

Make sure the folder exists with the proper permissions

chown mysql:mysql /var/lib/mysql/

And make sure to delete the file so the mysql server could generate a new one

rm /var/lib/mysql/mysql.sock.lock

Posting this answer, in case it helps someone with the same config as me. I had similar issue with this configuration:

Host OS: Ubuntu 20.04, MySql server: 8.0

The following error was seen in /var/log/mysql/error.log during run of systemctl start mysql

[ERROR] [MY-010273] [Server] Could not create unix socket lock file /var/run/mysqld/mysqld.sock.lock.

Fix was similar:

mkdir -p /var/run/mysqld/
chmod 777 /var/run/mysqld/

And of course, I had enough space wherever mysql server was being installed.

I just ran into this. The mysql install was a little weird and was missing /var/run/mysqld/

MySQLd was attempting to create the socket and lock file but the parent directory was missing. I simply created the directory

sudo mkdir /var/run/mysqld

chowned it to mysql

sudo chown mysql:mysql /var/run/mysqld

I was then able to start mysqld normally.