Why is “mysqld.pid” and “mysqld.sock” missing from my system even though the values are set in “my.cnf?”

I was working on an answer to this question—on one of my Ubuntu 12.04.5 development servers—and realized that the MySQL install was not creating mysqld.pid and mysqld.sock files despite their paths being explicitly set in my.cnf like this:

[mysqld] # # * Basic Settings # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp lc-messages-dir = /usr/share/mysql skip-external-locking 

Why would this happen and what can be done to resolve the issue?

1 Answer

Even though the locations for mysqld.pid and mysqld.sock are set in my server’s my.cnf, the directory doesn’t exist so those files are never created. This will fix that:

First create the mysqld/ directory in /var/run/ like this:

sudo mkdir -p /var/run/mysqld/ 

Then create a mysqld.pid file with touch:

sudo touch /var/run/mysqld/mysqld.pid 

Next create a mysqld.sock file with touch:

sudo touch /var/run/mysqld/mysqld.sock 

Now change the ownerships of the directory and files to mysql:mysql like this:

sudo chown mysql:mysql -R /var/run/mysqld 

And restart MySQL like this to get those files set and created:

sudo service mysql restart 

When that’s all done, MySQL will be able to to create the mysqld.pid and mysqld.sock files as expected.

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