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)]>
