[mysql error]The server quit without updating PID file

update: 2017年7月11日17:42

终极解决方案：
用brew安装mysql经常会碰到这些问题，直接用安装包安装后，从未复现

debug前须知：
mysql配置文件依次读取：

/etc/my.cnf
/etc/mysql/my.cnf
~/my.cnf

网上提供的解决方法：

查看报错信息，有两处报错

err文件位于/usr/local/var/mysql/data

- Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
按照提示运行`mysql_upgrade`报错

​ >mysql_upgrade: Got error: 2002: Can’t connect to local MySQL server through socket ‘/tmp/mysql.sock’ (2) while connecting to the MySQL server
Upgrade process encountered error and will not continue.

- Fatal error: Can't open and lock privilege tables: Table 'mysql.user' doesn't exist

检查是否有实例正在运行

ps -ef | grep mysql

结果：没有

删除.err文件

结果：无效

改变权限

sudo chown -R _mysql:mysql /usr/local/var/mysql

结果：无效

重新初始化

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

因为/usr/local/var/mysql/data目录不为空，所以没法初始化，那么先清空目录，再初始化

unset TMPDIR
cd /usr/local/var/mysql/data
sudo rm *
mysql_install_db

再运行sudo mysql.server start命令启动，依然报错，查看目录文件权限，原来初始化的时候又改变权限了

sudo chown -R _mysql:mysql /usr/local/var/mysql

DONE！

brew services start mysql与mysql.server start

2017-04-12T12:00:55.701485Z 1 [Note] A temporary password is generated for root@localhost: ZCBp1r-K0RlE

If you lose this password, please consult the section How to Reset the Root Password in the MySQL reference manual.