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
