本文记录了RHEL7.5下mysql 8.0.11安装教程，具体内容如下
首先去mysql官网下载mysql-8.0.11-el7-x86_64.tar 解压。
由于mysql初始化、启动都需要用到mysql用户，所以创建一个mysql用户：
useradd -d /home/mysql -m -s /bin/bash mysql
经过测试发现系统中装有mariadb相关的mysql启动的时候会报错，于是卸载和mariadb相关的包。
[root@rhel mysql]# yum remove mariadb*Loaded plugins: axelget, fastestmirror, langpacks, product-id, search-disabled- : repos, subscription-managerThis system is not registered with an entitlement server. You can use subscription-manager to register.Resolving Dependencies--> Running transaction check---> Package mariadb-libs.x86_64 1:5.5.56-2.el7 will be erased--> Processing Dependency: libmysqlclient.so.18()(64bit) for package: 2:postfix-2.10.1-6.el7.x86_64--> Processing Dependency: libmysqlclient.so.18(libmysqlclient_18)(64bit) for package: 2:postfix-2.10.1-6.el7.x86_64--> Running transaction check---> Package postfix.x86_64 2:2.10.1-6.el7 will be erased--> Finished Dependency Resolutionepel/x86_64/group_gz | 266 kB 00:00 Dependencies Resolved================================================================================ Package Arch Version Repository Size================================================================================Removing: mariadb-libs x86_64 1:5.5.56-2.el7 @base 4.4 MRemoving for dependencies: postfix x86_64 2:2.10.1-6.el7 @base 12 MTransaction Summary================================================================================Remove 1 Package (+1 Dependent package)Installed size: 17 MIs this ok [y/N]: yDownloading packages:Running transaction checkRunning transaction testTransaction test succeededRunning transaction Erasing : 2:postfix-2.10.1-6.el7.x86_64 1/2 Erasing : 1:mariadb-libs-5.5.56-2.el7.x86_64 2/2 No metadata available for baseNo metadata available for codeNo metadata available for epelNo metadata available for extrasNo metadata available for updatesLoading mirror speeds from cached hostfile * base: mirrors.aliyun.com * epel: mirrors.ustc.edu.cn * extras: mirrors.aliyun.com * updates: mirrors.aliyun.comepel/x86_64/primary_db | 6.3 MB 00:01 Verifying : 1:mariadb-libs-5.5.56-2.el7.x86_64 1/2 Verifying : 2:postfix-2.10.1-6.el7.x86_64 2/2 Removed: mariadb-libs.x86_64 1:5.5.56-2.el7 Dependency Removed: postfix.x86_64 2:2.10.1-6.el7 Complete!
使用如下命令初始化数据库，会在把/var/lib/mysql作为data文件的目录：
shell> bin/mysqld --initialize --user=mysql
于是我们可以在初始化的时候指定相应的文件目录：
bin/mysqld --initialize --basedir=/home/mysql --datadir=/home/mysql/data --user=mysql
初始化的时候，会生成一个临时的密码，记住该密码，等登录到mysql的时候需要用这个密码，进去后再次修改密码。
启动mysql实例：
bin/mysqld --user=mysqlbin/mysqld_safe basedir=/home/mysql --datadir=/home/mysql/data --user=mysql
如果不加 –user=mysql 就会出现如下的提示：
2018-04-22T15:47:25.471462Z 0 [ERROR] [MY-010123] [Server] Fatal error: Please read "Security" section of the manual to find out how to run mysqld as root!2018-04-22T15:47:25.471514Z 0 [ERROR] [MY-010119] [Server] Aborting
造成mysql实例不能正常启动。
mysql启动后，使用root用户登录，使用刚刚随机生成的密码，进去后，通过如下命令修改root用户的密码，再做其他操作：
RHEL7的服务systemctl脚本存放在：/usr/lib/systemd/，有系统（system）和用户（user）之分，像需要开机不登陆就能运行的程序，还是存在系统服务里吧，即：/usr/lib/systemd/system目录下
每一个服务以.service结尾，一般会分为3部分：[Unit]、[Service]和[Install]，现在把MYSQL添加进去，具体内容如下：
cat /usr/lib/systemd/system/mysql.service[Unit]Description=mysql ServerAfter=Network.targetAfter=syslog.target[Install]WantedBy=multi-user.target[Service]User=mysqlGroup=mysqlType=forking# Execute pre and post scripts as rootPermissionsStartOnly=true# Start main serviceExecStart=/home/mysql/bin/mysqld --daemonizeExecStop=kill -s -QUIT $MAINPIDRestart=on-failureRestartPreventExitStatus=1PrivateTmp=false
就可以通过systemctl来 启动，重启，关闭mysql服务。
注：相关教程知识阅读请移步到MYSQL教程频道。
