centos7上配置MySQL5.7的開機自啟動方法

centos7開始使得以往老版本系統服務的/etc/init.d的啟動指令碼的方式就此改變，在centos7中所有對服務的管理都集中到了systemctl當中。
systemctl是一個系統管理守護程式、工具和庫的集合，用於取代以往的System V、service和chkconfig命令。

建立用於啟動MySQL的配置檔案
[root@localhost ~]# touch /usr/lib/systemd/system/mysqld.service
[root@localhost ~]# cd /usr/lib/systemd/system

編輯mysqld.service檔案，加入如下內容:
[root@localhost system]# vi mysqld.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

[Service]
User=mysql
Group=mysql
ExecStart=/opt/mysql-5.7.18/bin/mysqld --defaults-file=/etc/my.cnf
LimitNOFILE = 5000
儲存退出

備註:ExecStart=/opt/mysql-5.7.18/bin/mysqld (此處請對應修改為MySQL程式所在的路徑)
查詢mysqld路徑,例如:
[root@localhost system]# which mysqld
/opt/mysql-5.7.18/bin/mysqld


透過systemctl方式啟動mysql5.7:
[root@localhost system]# systemctl start mysqld


檢查MySQL執行狀態:
[root@localhost system]# mysql -p 
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.18-log MySQL Community Server (GPL)


Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.


Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.


Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.


mysql> 
mysql> 
mysql> \s
--------------
mysql  Ver 14.14 Distrib 5.7.18, for linux-glibc2.5 (x86_64) using  EditLine wrapper


Connection id: 6
Current database:
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.18-log MySQL Community Server (GPL)
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: latin1
Db     characterset: latin1
Client characterset: utf8
Conn.  characterset: utf8
UNIX socket: /tmp/mysql.sock
Uptime: 45 sec


Threads: 3  Questions: 6  Slow queries: 0  Opens: 108  Flush tables: 1  Open tables: 101  Queries per second avg: 0.133
--------------

mysql> 

關閉防火牆:
[root@localhost system]# systemctl stop firewalld.service
[root@localhost system]# systemctl disable firewalld.service
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

設定mysql的開機啟動：
[root@localhost system]# systemctl enable mysqld
Created symlink from /etc/systemd/system/multi-user.target.wants/mysqld.service to /usr/lib/systemd/system/mysqld.service.
[root@localhost system]# systemctl list-unit-files | grep mysqld
mysqld.service                                enabled 


取消mysql的開機自啟動:
[root@localhost system]# systemctl disable mysqld
Removed symlink /etc/systemd/system/multi-user.target.wants/mysqld.service.
[root@localhost system]# systemctl list-unit-files | grep mysqld
mysqld.service                                disabled