以前的Linux系统中数据库大部分是mysql，不过自从被sun收购之后，就没用集成在centos这些开源Linux系统中了，那么如果想用的话就需要自己安装了，首先centos7 已经不支持mysql，因为收费了你懂得，所以内部集成了mariadb，而安装mysql的话会和mariadb的文件冲突，所以需要先卸载掉mariadb，以下为卸载mariadb，安装mysql的步骤。

#列出所有被安装的rpm package

rpm -qa | grep mariadb

#卸载

rpm -e mariadb-libs-5.5.37-1.el7_0.x86_64

错误：依赖检测失败：

        libmysqlclient.so.18()(64bit) 被 (已安裝) postfix-2:2.10.1-6.el7.x86_64 需要

        libmysqlclient.so.18(libmysqlclient_18)(64bit) 被 (已安裝) postfix-2:2.10.1-6.el7.x86_64 需要

#强制卸载，因为没有--nodeps

rpm -e --nodeps mariadb-libs-5.5.37-1.el7_0.x86_64

#安装mysql5.5.39的rpm包

rpm -ivh /home/liwei/MySQL-server-5.5.39-2.el6.x86_64.rpm

rpm -ivh /home/liwei/MySQL-client-5.5.39-2.el6.x86_64.rpm

#拷贝配置文件

cp /usr/share/mysql/my-medium.cnf /etc/my.cnf，改名为my.cnf作为mysql配置文件。

#修改响应的配置文件

vim /etc/my.cnf

#把mysql的data拷贝到制定的目录

mv /var/lib/mysql　/home/mysql/data/

还要注意目录的属主和权限。

MYSQL启动后报：ERROR! The server quit without updating PID file错误的问题解决

1、权限不够：chown -R mysql:mysql /home/mysql/data” “chmod -R 755 /home/mysql/data

2、centos7的selinux问题：打开/etc/selinux/config，把SELINUX=enforcing改为SELINUX

centos7 安装 mariadb 的正确命令

使用的是linode的centos7系统，安装mysql发现已经默认的是mariadb。

但是不管是使用linode官网说明还是百度搜索到的的根本安装方法无法安装成功。

总是提示这一句：

ERROR 2002 (HY000): Can't connect to local Mysql server through socket '/var/lib/mysql/mysql.sock' (2)

最后通过google 搜索 install mariadb on centos 7得到了安装的关键一步。

现在安装成功，特此备注一下整个安装过程：

mysql:[root@localhost ~]# yum -y install mariadb* 

Loaded plugins: fastestmirror 

Loading mirror speeds from cached hostfile  

 * base: mirrors.linode.com  

 * extras: mirrors.linode.com  

 * updates: mirrors.linode.com 

Resolving Dependencies 

--> Running transaction check 

---> Package mariadb.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-bench.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-devel.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-embedded.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-embedded-devel.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-libs.x86_64 1:5.5.37-1.el7_0 will be installed 

---> Package mariadb-server.x86_64 1:5.5.37-1.el7_0 will be installed 

--> Processing Dependency: perl-DBD-MySQL for package: 1:mariadb-server-5.5.37-1.el7_0.x86_64 

---> Package mariadb-test.x86_64 1:5.5.37-1.el7_0 will be installed 

--> Running transaction check 

---> Package perl-DBD-MySQL.x86_64 0:4.023-5.el7 will be installed 

--> Finished Dependency Resolution 

Dependencies Resolved 

==========================================================================================================  

 Package                           Arch              Version                     Repository          Size 

========================================================================================================== 

Installing:  

 mariadb                           x86_64            1:5.5.37-1.el7_0            updates            8.9 M  

 mariadb-bench                     x86_64            1:5.5.37-1.el7_0            updates            385 k  

 mariadb-devel                     x86_64            1:5.5.37-1.el7_0            updates            744 k  

 mariadb-embedded                  x86_64            1:5.5.37-1.el7_0            updates            3.6 M  

 mariadb-embedded-devel            x86_64            1:5.5.37-1.el7_0            updates            7.4 M  

 mariadb-libs                      x86_64            1:5.5.37-1.el7_0            updates            752 k  

 mariadb-server                    x86_64            1:5.5.37-1.el7_0            updates             11 M  

 mariadb-test                      x86_64            1:5.5.37-1.el7_0            updates            7.9 M 

Installing for dependencies:  

 perl-DBD-MySQL                    x86_64            4.023-5.el7                 base               140 k 

Transaction Summary 

========================================================================================================== 

Install  8 Packages (+1 Dependent package) 

Total download size: 40 M 

Installed size: 279 M 

Downloading packages: 

(1/9): mariadb-bench-5.5.37-1.el7_0.x86_64.rpm                                     | 385 kB  00:00:00 

(2/9): mariadb-devel-5.5.37-1.el7_0.x86_64.rpm                                     | 744 kB  00:00:00 

(3/9): mariadb-embedded-5.5.37-1.el7_0.x86_64.rpm                                  | 3.6 MB  00:00:00 

(4/9): mariadb-5.5.37-1.el7_0.x86_64.rpm                                           | 8.9 MB  00:00:00 

(5/9): mariadb-libs-5.5.37-1.el7_0.x86_64.rpm                                      | 752 kB  00:00:00 

(6/9): mariadb-server-5.5.37-1.el7_0.x86_64.rpm                                    |  11 MB  00:00:00 

(7/9): mariadb-embedded-devel-5.5.37-1.el7_0.x86_64.rpm                            | 7.4 MB  00:00:00 

(8/9): mariadb-test-5.5.37-1.el7_0.x86_64.rpm                                      | 7.9 MB  00:00:00 

(9/9): perl-DBD-MySQL-4.023-5.el7.x86_64.rpm                                       | 140 kB  00:00:00 

---------------------------------------------------------------------------------------------------------- 

Total                                                                      36 MB/s |  40 MB  00:00:01 

Running transaction check 

Running transaction test 

Transaction test succeeded 

Running transaction  

  Installing : 1:mariadb-libs-5.5.37-1.el7_0.x86_64                                                   1/9  

  Installing : 1:mariadb-5.5.37-1.el7_0.x86_64                                                        2/9  

  Installing : perl-DBD-MySQL-4.023-5.el7.x86_64                                                      3/9  

  Installing : 1:mariadb-server-5.5.37-1.el7_0.x86_64                                                 4/9  

  Installing : 1:mariadb-devel-5.5.37-1.el7_0.x86_64                                                  5/9  

  Installing : 1:mariadb-embedded-5.5.37-1.el7_0.x86_64                                               6/9  

  Installing : 1:mariadb-embedded-devel-5.5.37-1.el7_0.x86_64                                         7/9  

  Installing : 1:mariadb-test-5.5.37-1.el7_0.x86_64                                                   8/9  

  Installing : 1:mariadb-bench-5.5.37-1.el7_0.x86_64                                                  9/9  

  Verifying  : 1:mariadb-test-5.5.37-1.el7_0.x86_64                                                   1/9  

  Verifying  : 1:mariadb-embedded-devel-5.5.37-1.el7_0.x86_64                                         2/9  

  Verifying  : 1:mariadb-embedded-5.5.37-1.el7_0.x86_64                                               3/9  

  Verifying  : 1:mariadb-libs-5.5.37-1.el7_0.x86_64                                                   4/9  

  Verifying  : 1:mariadb-bench-5.5.37-1.el7_0.x86_64                                                  5/9  

  Verifying  : 1:mariadb-5.5.37-1.el7_0.x86_64                                                        6/9  

  Verifying  : 1:mariadb-server-5.5.37-1.el7_0.x86_64                                                 7/9  

  Verifying  : perl-DBD-MySQL-4.023-5.el7.x86_64                                                      8/9  

  Verifying  : 1:mariadb-devel-5.5.37-1.el7_0.x86_64                                                  9/9 

Installed:  

  mariadb.x86_64 1:5.5.37-1.el7_0                        mariadb-bench.x86_64 1:5.5.37-1.el7_0  

  mariadb-devel.x86_64 1:5.5.37-1.el7_0                  mariadb-embedded.x86_64 1:5.5.37-1.el7_0  

  mariadb-embedded-devel.x86_64 1:5.5.37-1.el7_0         mariadb-libs.x86_64 1:5.5.37-1.el7_0  

  mariadb-server.x86_64 1:5.5.37-1.el7_0                 mariadb-test.x86_64 1:5.5.37-1.el7_0 

Dependency Installed:  

  perl-DBD-MySQL.x86_64 0:4.023-5.el7 

Complete! 

[root@localhost ~]# systemctl start mariadb.service 

[root@localhost ~]# systemctl enable mariadb.service 

ln -s '/usr/lib/systemd/system/mariadb.service' '/etc/systemd/system/multi-user.target.wants/mariadb.servi                      

ce' 

[root@localhost ~]# mysql 

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

Your MariaDB connection id is 2 

Server version: 5.5.37-MariaDB MariaDB Server 

Copyright (c) 2000, 2014, Oracle, Monty Program Ab and others. 

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. 

MariaDB [(none)]> logout  

    -> exit  

    ->  

    -> ; 

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaD                      

B server version for the right syntax to use near 'logout 

exit' at line 1 

MariaDB [(none)]> exit 

Bye 

[root@localhost ~]# systemctl enable mariadb.service 

[root@localhost ~]# mysql 

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

Your MariaDB connection id is 3 

Server version: 5.5.37-MariaDB MariaDB Server 

Copyright (c) 2000, 2014, Oracle, Monty Program Ab and others. 

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. 

MariaDB [(none)]> show databases; 

+--------------------+ 

| Database           | 

+--------------------+ 

| information_schema | 

| mysql              | 

| performance_schema | 

| test               | 

+--------------------+ 

4 rows in set (0.00 sec) 

MariaDB [(none)]> use test 

Database changed 

MariaDB [test]> show tables; 

Empty set (0.00 sec) 

MariaDB [test]> exit 

Bye 

[root@localhost ~]# mysql_secure_installation 

/usr/bin/mysql_secure_installation: line 379: find_mysql_client: command not found 

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB  

      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY! 

In order to log into MariaDB to secure it, we'll need the current 

password for the root user.  If you've just installed MariaDB, and 

you haven't set the root password yet, the password will be blank, 

so you should just press enter here. 

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) 

Enter current password for root (enter for none): 

OK, successfully used password, moving on... 

Setting the root password ensures that nobody can log into the MariaDB 

root user without the proper authorisation. 

Set root password? [Y/n] y 

New password: 

Re-enter new password: 

Password updated successfully! 

Reloading privilege tables..  

 ... Success! 

By default, a MariaDB installation has an anonymous user, allowing anyone 

to log into MariaDB without having to have a user account created for 

them.  This is intended only for testing, and to make the installation 

go a bit smoother.  You should remove them before moving into a 

production environment. 

Remove anonymous users? [Y/n] y  

 ... Success! 

Normally, root should only be allowed to connect from 'localhost'.  This 

ensures that someone cannot guess at the root password from the network. 

Disallow root login remotely? [Y/n] y  

 ... Success! 

By default, MariaDB comes with a database named 'test' that anyone can 

access.  This is also intended only for testing, and should be removed 

before moving into a production environment. 

Remove test database and access to it? [Y/n] y  

 - Dropping test database...  

 ... Success!  

 - Removing privileges on test database...  

 ... Success! 

Reloading the privilege tables will ensure that all changes made so far 

will take effect immediately. 

Reload privilege tables now? [Y/n] y  

 ... Success! 

Cleaning up... 

All done!  If you've completed all of the above steps, your MariaDB 

installation should now be secure. 

Thanks for using MariaDB! 

[root@localhost ~]# mysql -uroot -p 

Enter password: 

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

Your MariaDB connection id is 15 

Server version: 5.5.37-MariaDB MariaDB Server 

Copyright (c) 2000, 2014, Oracle, Monty Program Ab and others. 

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. 

MariaDB [(none)]> show databases; 

+--------------------+ 

| Database           | 

+--------------------+ 

| information_schema | 

| mysql              | 

| performance_schema | 

| zbphp.com          | 

+--------------------+ 

4 rows in set (0.00 sec) 

MariaDB [(none)]>