新购买了一个云服务器，上面没有安装mysql服务，今天从0开始安装mysql服务。

由于中间遇到不顺利的情节，所以把他记录下来，便于以后参考。

本文适用于 CentOS 7 与 CentOS 6 上安装Mysql服务器。

一、要下载的Mysql安装相关文件（共4个）：

1）mysql-community-libs-5.7.28-1.el7.x86_64.rpm
https://downloads.mysql.com/archives/get/p/23/file/mysql-community-libs-5.7.28-1.el7.x86_64.rpm

2）mysql-community-common-5.7.28-1.el7.x86_64.rpm
https://downloads.mysql.com/archives/get/p/23/file/mysql-community-common-5.7.28-1.el7.x86_64.rpm

3）mysql-community-client-5.7.28-1.el7.x86_64.rpm
https://downloads.mysql.com/archives/get/p/23/file/mysql-community-client-5.7.28-1.el7.x86_64.rpm

4）mysql-community-server-5.7.28-1.el7.x86_64.rpm
https://downloads.mysql.com/archives/get/p/23/file/mysql-community-server-5.7.28-1.el7.x86_64.rpm

以上这些文件我已经添加了URL，不必访问Oracle网站，直接点击就可下载。

进入linux系统，执行如下命令进行下载：

cd /
mkdir mysql_install
cd mysql_install

wget https://downloads.mysql.com/archives/get/p/23/file/mysql-community-libs-5.7.28-1.el7.x86_64.rpm
wget https://downloads.mysql.com/archives/get/p/23/file/mysql-community-common-5.7.28-1.el7.x86_64.rpm
wget https://downloads.mysql.com/archives/get/p/23/file/mysql-community-client-5.7.28-1.el7.x86_64.rpm
wget https://downloads.mysql.com/archives/get/p/23/file/mysql-community-server-5.7.28-1.el7.x86_64.rpm

注意需要按顺序安装以上RPM包，安装顺序如下：

rpm -ivh mysql-community-common-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-libs-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-client-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-server-5.7.28-1.el7.x86_64.rpm

出现如下错误： 

error: Failed dependencies:
        libncurses.so.5()(64bit) is needed by mysql-community-client-5.7.28-1.el7.x86_64
        libtinfo.so.5()(64bit) is needed by mysql-community-client-5.7.28-1.el7.x86_64

yum install libncurses*

在安装 执行 rpm -ivh mysql-community-client-5.7.28-1.el7.x86_64.rpm 时，出现如下错误：

error: Failed dependencies:
        libncurses.so.5()(64bit) is needed by mysql-community-client-5.7.28-1.el7.x86_64
        libtinfo.so.5()(64bit) is needed by mysql-community-client-5.7.28-1.el7.x86_64

执行如下命令安装 libncurses
yum install libncurses*

从 rpm -ivh mysql-community-client-5.7.28-1.el7.x86_64.rpm 重新执行，结果如下：

rpm -ivh mysql-community-common-5.7.28-1.el7.x86_64.rpm
warning: mysql-community-common-5.7.28-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
        package mysql-community-common-5.7.28-1.el7.x86_64 is already installed

rpm -ivh mysql-community-libs-5.7.28-1.el7.x86_64.rpm
warning: mysql-community-libs-5.7.28-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
        package mysql-community-libs-5.7.28-1.el7.x86_64 is already installed

rpm -ivh mysql-community-client-5.7.28-1.el7.x86_64.rpm
warning: mysql-community-client-5.7.28-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
Updating / installing...
   1:mysql-community-client-5.7.28-1.e################################# [100%]

rpm -ivh mysql-community-server-5.7.28-1.el7.x86_64.rpm
warning: mysql-community-server-5.7.28-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
Updating / installing...
   1:mysql-community-server-5.7.28-1.e################################# [100%]

至此，mysql所用到的文件安装成功！

安装完成后，mysql安装程序会创建mysql这个系统帐号，如果不存在，请用如下命令创建mysql用户：

groupadd mysql
useradd -r -g mysql mysql

二、修改配置文件

mysql的服务安装成功后，
服务器程序文件位置在 ：   /usr/sbin/mysqld，
同时配置文件位置在： /etc/my.cnf，
客户端程序位置在：  /usr/bin/mysql

修改配置文件，输入如下命令：

vi /etc/my.cnf

修改后的配置文件如下：

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html

#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
[client]
socket=/home/mysql-5.7.28/mysql.sock
[mysqld]
explicit_defaults_for_timestamp=true
datadir=/home/mysql-5.7.28/data
socket=/home/mysql-5.7.28/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

log-error=/home/mysql-5.7.28/log/mysqld.log
pid-file=/home/mysql-5.7.28/mysqld.pid

my.cnf文件原来有内容，我将配置文件当中的目录一律改为 /home/mysql-5.7.28，这样便于以后升级或安装多个版本的mysql服务。注意，要设置好mysql客户端的socket，如下：

[client]
socket=/home/mysql-5.7.28/mysql.sock

如果未添加以上配置，则用mysql客户端时会提示找不到socket文件。

然后创建/home/mysql-5.7.28目录，命令如下：

cd /home
mkdir mysql-5.7.28
mkdir mysql-5.7.28/data
mkdir mysql-5.7.28/log
chown -R mysql:mysql mysql-5.7.28

三、首次启动mysqld服务，执行初始化与修改root密码

在命令好键入如下命令（不能用systemctl命令，CentOS7以上才支持，只能用service命令）： 

service mysqld start

这个命令将执行初始化数据库操作，创建初始数据库。

执行完成，如果没有错误，会创建一个root用户，并设置一个临时口令，必须修改这个口令才能对mysql数据库进行下一步操作，请修改root用户的口令，用如下命令查看这个临时口令：

cat /home/mysql-5.7.28/log/mysqld.log | grep password

查看的结果如下：

2019-10-30T11:29:10.750559Z 0 [Note] Shutting down plugin 'sha256_password'
2019-10-30T11:29:10.750562Z 0 [Note] Shutting down plugin 'mysql_native_password'
2019-10-30T11:46:55.703659Z 1 [Note] A temporary password is generated for root@localhost: ftW61Ogr=IRM
2019-10-30T11:47:59.235604Z 2 [Note] Access denied for user 'UNKNOWN_MYSQL_USER'@'localhost' (using password: NO)
2019-10-30T11:48:05.209678Z 0 [Note] Shutting down plugin 'validate_password'
2019-10-30T11:48:06.523413Z 0 [Note] Shutting down plugin 'sha256_password'
2019-10-30T11:48:06.523416Z 0 [Note] Shutting down plugin 'mysql_native_password'

字符串：ftW61Ogr=IRM 就是临时口令。

在命令行里键入如下mysql客户端：

mysql -u root -p

输入如上临时口令；成功后将进入mysql命令环境。如下所示，即表示安装mysql成功。

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.28

Copyright (c) 2000, 2019, 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.

在mysql命令行环境里执行： show databases; 将会看到如下提示：

You must reset your password using ALTER USER statement before executing this statement.

必须重置mysql的root用户口令，才能进一步操作。

由于mysql安装完成后初始化对命令的校验级别比较高，修改命令不会成功的，因此用如下命令修改命令的校验级别：

set global validate_password_policy=LOW;

然后用如下命令修改mysql的root口令：

ALTER USER 'root'@'localhost' IDENTIFIED BY 'lyh@26670927';

root用户的口令修改为 lyh@26670927，提示如下：

Query OK, 0 rows affected (0.00 sec)

再次敲入：show databases; 出现如下结果：

 show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

至此，mysql数据库全部安装成功，就可以用PHP，java来访问了。