pid文件位置问题：

cat /etc/systemd/system/mysql.service

[Unit]

Description=MySQL Server

Documentation=man:mysqld(8)

Documentation=http://dev.mysql.com/doc/refman/en/using-systemd.html

After=network.target

After=syslog.target

[Install]

WantedBy=multi-user.target

Alias=mysql.service

[Service]

User=mysql

Group=mysql

Type=forking

PIDFile=/var/lib/mysql/Devops-mysql-slave-150.pid   //修改为正确的mysql pid位置

# Disable service start and stop timeout logic of systemd for mysqld service.

TimeoutSec=0

# Execute pre and post scripts as root

PermissionsStartOnly=true

# Needed to create system tables

ExecStartPre=/usr/bin/mysqld_pre_systemd

# Start main service

ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/lib/mysql/Devops-mysql-slave-150.pid $MYSQLD_OPTS    ## 修改pid位置

# Use this to switch malloc implementation

EnvironmentFile=-/etc/sysconfig/mysql

# Sets open_files_limit

LimitNOFILE = 5000

Restart=on-failure

RestartPreventExitStatus=1

PrivateTmp=false

启动 ：

systemctl start mysql.service

如果嫌mysql.service 麻烦  ，可以修改Alias=mysql.service为mysqld

systemctl start mysqld