Unable to check the Mysql/Mariadb status after upgrade: ERROR! MariaDB is running but PID file could not be found

Symptoms

• Unable to check the Mysql/Mariadb status:

  # systemctl status mariadb
  ERROR! MariaDB is running but PID file could not be found

• Mysql/Mariadb may fail with such error as well:

  ERROR 2002 (HY000): Can't connect to local server through socket '/var/lib/mysql/mysql.sock' (111)

• Mysql/MariaDB was upgraded according to KB article How to upgrade MySQL 5.5 to 5.6/5.7 or MariaDB 5.5 to 10.x on Linux

• /var/run/mariadb directory doesn't exist:

  # ls -la /var/run/mariadb
  ls: cannot access /var/run/mariadb: No such file or directory

Cause

There is no PID file for a Mysql/Mariadb server.

Resolution

1. Connect to the server using SSH

2. Create a /var/run/mariadb directory and set ownership:

   # mkdir /var/run/mariadb

   # chown mysql:mysql /var/run/mariadb
   /var/run/mariadb: directory

3. Restart Mysql/Mariadb service:

   # systemctl restart mariadb.service