PID error on mysql.server start?

I ran into the same issue while trying to install MySQL 5.5.15 in Lion using homebrew and resolved the issue with:

mysql_install_db --verbose --user=`whoami` --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp

and creating a the file ~/my.cnf

with the content:

 [mysqld]
   basedir=/usr/local/Cellar/mysql/5.5.15
   datadir=/usr/local/var/mysql

basedir - should be your current MySQL instalation dir datadir - should be the location of MySQL data

You can figure out that too location by watching the make command during the "brew install mysql" searching for something like this:

-DCMAKE_INSTALL_PREFIX=/usr/local/Cellar/mysql/5.5.15 -DMYSQL_DATADIR=/usr/local/var/mysql -DINSTALL_MANDIR=/usr/local/Cellar/mysql

Where DCMAKE_INSTALL_PREFIX = basedir and DMYSQL_DATADIR = datadir

You probably need to ensure that you're running mysql as the root user -- otherwise it won't have permission to write the PID file (thus the error you're receiving).

Try this:

sudo mysql.server start

You'll be prompted for your password. (this assumes that your user account has permissions to "sudo" -- which it should, unless it's setup as a restricted user account in OS X).

This may not be the only issue -- but it should get you to the next step anyway.

I ran into this same problem when installing via homebrew. Make sure you run these commands (which are listed during install but easy to miss):

unset TMPDIR
mysql_install_db

Nothing else really helped, but the following worked:

$ ps aux | grep mysql
tagir           27260   0.0  1.0  3562356 175120   ??  S     2:52PM   0:00.42 mysqld --skip-grant-tables
tagir           42704   0.0  0.0  2434840    784 s000  S+    3:04PM   0:00.00 grep mysql
$ kill 27260
# Careful! This might erase your existing data
$ rm -rf /usr/local/var/mysql
$ mysqld --initialize
$ mysql.server start