useradd -d /home/mysql -m -s /bin/bash mysql

[root@rhel mysql]# yum remove mariadb*
Loaded plugins: axelget, fastestmirror, langpacks, product-id, search-disabled-
  : repos, subscription-manager
This 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 Resolution
epel/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 M
Removing for dependencies:
 postfix  x86_64  2:2.10.1-6.el7  @base  12 M

Transaction Summary
================================================================================
Remove 1 Package (+1 Dependent package)

Installed size: 17 M
Is this ok [y/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running 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 base
No metadata available for code
No metadata available for epel
No metadata available for extras
No metadata available for updates
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * epel: mirrors.ustc.edu.cn
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
epel/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!

shell> bin/mysqld --initialize --user=mysql

bin/mysqld --initialize --basedir=/home/mysql --datadir=/home/mysql/data --user=mysql

bin/mysqld --user=mysql
bin/mysqld_safe basedir=/home/mysql --datadir=/home/mysql/data --user=mysql

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

set password ='root';

cat /usr/lib/systemd/system/mysql.service
[Unit]
Description=mysql Server
After=Network.target
After=syslog.target

[Install]
WantedBy=multi-user.target

[Service]
User=mysql
Group=mysql

Type=forking
# Execute pre and post scripts as root
PermissionsStartOnly=true
# Start main service
ExecStart=/home/mysql/bin/mysqld --daemonize
ExecStop=kill -s -QUIT $MAINPID
Restart=on-failure
RestartPreventExitStatus=1
PrivateTmp=false