一   检查本地是否安装过其他版本的mysql

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -qa|grep -i  mysql
MySQL-server-5.5.59-1.el7.x86_64
MySQL-client-5.5.59-1.el7.x86_64
MySQL-devel-5.5.59-1.el7.x86_64

二    若是安装过需要先卸载

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -e  --nodeps  MySQL-server-5.5.59-1.el7.x86_64 

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -e  --nodeps  MySQL-client-5.5.59-1.el7.x86_64

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -e  --nodeps  MySQL-devel-5.5.59-1.el7.x86_64

三   由于有些版本自带的有mariadb（本质是mysql，只是名字不一样而已），需要先检查是否有mariadb，若有则卸载

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -qa|grep -i  mariadb

 

 mariadb-libs-5.5.52-1.el7.x86_64

四   卸载mariadb

[root@iZuf6ih01h8fzeziddwkfdZ opt]#  rpm -e  --nodeps  mariadb-libs-5.5.52-1.el7.x86_64

 

五  下载mysql 5.5的服务器和客户端的安装包

[root@iZuf6ih01h8fzeziddwkfdZ opt]# wget https://dev.mysql.com/get/Downloads/MySQL-5.5/MySQL-server-5.5.59-1.el7.x86_64.rpm

[root@iZuf6ih01h8fzeziddwkfdZ opt]# wget https://dev.mysql.com/get/Downloads/MySQL-5.5/MySQL-client-5.5.59-1.el7.x86_64.rpm

六  安装服务器和客户端

[root@iZuf6ih01h8fzeziddwkfdZ opt]# rpm -ivh MySQL-server-5.5.59-1.el7.x86_64.rpm 

warning: MySQL-server-5.5.59-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:MySQL-server-5.5.59-1.el7        ################################# [100%]
warning: user mysql does not exist - using root
warning: group mysql does not exist - using root
180118 22:52:25 [Note] Ignoring --secure-file-priv value as server is running with --bootstrap.
180118 22:52:25 [Note] /usr/sbin/mysqld (mysqld 5.5.59) starting as process 19043 ...
180118 22:52:26 [Note] Ignoring --secure-file-priv value as server is running with --bootstrap.
180118 22:52:26 [Note] /usr/sbin/mysqld (mysqld 5.5.59) starting as process 19049 ...

PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:

/usr/bin/mysqladmin -u root password 'new-password'
/usr/bin/mysqladmin -u root -h iZuf6ih01h8fzeziddwkfdZ password 'new-password'

Alternatively you can run:
/usr/bin/mysql_secure_installation

which will also give you the option of removing the test
databases and anonymous user created by default.  This is
strongly recommended for production servers.
See the manual for more instructions.


Please report any problems at http://bugs.mysql.com/

[root@iZuf6ih01h8fzeziddwkfdZ opt]# rpm -ivh MySQL-client-5.5.59-1.el7.x86_64.rpm

warning: MySQL-client-5.5.59-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:MySQL-client-5.5.59-1.el7        ################################# [100%]

七   启动mysql 设置密码

 启动mysql （第一次启动mysql是不需要密码的）

[root@iZuf6ih01h8fzeziddwkfdZ opt]# service mysql start

Starting MySQL.Logging to '/var/lib/mysql/iZuf6ih01h8fzeziddwkfdZ.err'.
.                                                          [  OK  ]

进入mysql  至此mysql安装完毕

[root@iZuf6ih01h8fzeziddwkfdZ opt]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.59 MySQL Community Server (GPL)
Copyright (c) 2000, 2018, 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> 

退出mysql 修改密码（此时只是退出mysql，不能关掉mysql服务，否则将修改失败）

mysql> exit
Bye
[root@iZuf6ih01h8fzeziddwkfdZ opt]# /usr/bin/mysqladmin -u root password  你的密码

八  将mysql添加到开机启动项

至此全部完成，附带libaio依赖的下载及mysql的停止命令和随机启动

wget http://mirror.centos.org/centos/6/os/x86_64/Packages/libaio-0.3.107-10.el6.x86_64.rpm

mysql的停止命令  service mysql stop

mysql的随机启动命令  chkconfig mysql on

检查mysql 随机启动是否设置成功

[root@iZuf6ih01h8fzeziddwkfdZ opt]# chkconfig  --list|grep mysql


Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.
      If you want to list systemd services use 'systemctl list-unit-files'.
      To see services enabled on particular target use
      'systemctl list-dependencies [target]'.

mysql           0:off 1:off 2:on 3:on 4:on 5:on 6:off

 

八  查看my.cnf配置文件的位置

      这篇博客描写的的很详细：https://www.cnblogs.com/freewsf/p/11980721.html