What the hell is wrong with my sql?

[tony balony]

Mysql is the most confusing piece of software I have ever used.
Here is the thing, I have mysql 5.7.20 installed on the Mac High Sierra.
I use sudo /usr/local/mysql/support-files/mysql.server stop
It gave me ERROR! MySQL server PID file could not be found!
After some googling, I found I had to do this:
sudo mkdir /var/run/mysqld
sudo touch /var/run/mysqld/mysqld.pid
sudo chown -R mysql:mysql /var/run/mysqld
then did I use sudo /usr/local/mysql/support-files/mysql.server stop start a few times, it works fine.
However, once the Mac restarts, the /var/run/mysqld/mysqld.pid directory is gone. what's up with that? Thanks