mysql 5.5 的安装步骤：

1 软件安装

[root@dg2 ~]# rpm -ivh MySQL-server-advanced-5.5.54-1.el6.x86_64.rpm

warning: MySQL-server-advanced-5.5.54-1.el6.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY

Preparing...                ########################################### [100%]

1:MySQL-server-advanced  ########################################### [100%]

[root@dg2 ~]# rpm -qa |grep MySQL

MySQL-server-advanced-5.5.54-1.el6.x86_64

MySQL-shared-compat-advanced-5.5.54-1.el6.x86_64

MySQL-client-advanced-5.5.54-1.el6.x86_64

--直接重启会失败

[root@dg2 mysql]# service mysql restart  ERROR! MySQL server PID file could not be found!

Starting MySQL.Logging to '/var/lib/mysql/dg2.err'.

.... ERROR! The server quit without updating PID file (/var/lib/mysql/dg2.pid).

--必须通过mysql_install_db 进行初始化，才能重启成功 mysql_install_db --user=mysql --basedir=/var/lib/mysql --datadir=/var/lib/mysql

或者

/usr/bin/mysql_install_db  --user=mysql

[root@dg2 ~]# service mysql restart

Shutting down MySQL.... SUCCESS!

Starting MySQL... SUCCESS!

登录mysql不用密码，直接登录

[root@dg2 ~]# mysql

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 1

Server version: 5.5.54-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)

Copyright (c) 2000, 2016, 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>

修改密码的方式

update user set password=password('mysql') where user='root' and host='localhost';

mysql 5.7 的安装方式

---安装数据库软件

rpm -ivh mysql-community-common-5.7.9-1.el7.x86_64.rpm

rpm -ivh mysql-community-libs-5.7.9-1.el7.x86_64.rpm

rpm -ivh mysql-community-client-5.7.9-1.el7.x86_64.rpm

rpm -ivh mysql-community-server-5.7.9-1.el7.x86_64.rpm

[root@dg ]# rpm -ivh mysql-commercial-server-5.7.18-1.1.el6.x86_64.rpm

warning: mysql-commercial-server-5.7.18-1.1.el6.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY

Preparing...                ########################################### [100%]

1:mysql-commercial-server########################################### [100%]

[root@dg tmp]# rpm -qa |grep MySQL

perl-DBD-MySQL-4.013-3.el6.x86_64

MySQL-server-advanced-5.5.54-1.el6.x86_64

MySQL-devel-advanced-5.5.54-1.el6.x86_64

MySQL-shared-compat-5.6.35-1.el6.x86_64

MySQL-client-advanced-5.5.54-1.el6.x86_64

---初始化数据

/usr/sbin/mysqld --initialize --user=mysql --basedir=/var/lib/mysql --datadir=/var/lib/mysql

----重启数据库

[root@dg log]# service mysqld restart

Stopping mysqld:                                           [  OK  ]

Starting mysqld:                                           [  OK  ]

---登录mysql，密码吗会在mysqld.log 中

[root@dg log]# cat mysqld.log  |grep password

2017-03-16T07:18:26.877377Z 1 [Note] A temporary password is generated for root@localhost: MwBV,Xdy<1Dm

mysql  -uroot -p 输入密码

---修改密码

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'Cz.123456';

Query OK, 0 rows affected (0.00 sec)

mysql>  update mysql.user set authentication_string=PASSWORD('Cz.123456') where user='root' and host='localhost';

Query OK, 1 row affected, 1 warning (0.00 sec)

Rows matched: 1  Changed: 1  Warnings: 1

结论：通过对比可以发现5.7版本有很多改进

1、初始化方面，mysql  5.5 习惯用mysql_install_db ，而在5.7版本开始推荐用--initialize 来初始化数据库

2、在登录方面，5.5在登录的时候回用空密码登录，而在5.7版本会产生随机密码在日志文件中

3、在修改密码方面，5.7 可以用alter user的方式直接修改密码，在5.5版本是没有的