解決系統自帶mysql解除安裝不乾淨或因已存在系統自帶mysql導致無法安裝需要的mysql問題

系統：CentOS 6.9，MySQL：MySql 5.6

一、解除安裝

檢視已經安裝的服務：
rpm -qa|grep -i mysql
-i 作用是不區分大小寫
可能出現結果：mysql-5.1.73-8.el6_8.x86_64

或者通過yum線上安裝過的會出現：
mysql-libs-5.1.73-8.el6_8.x86_64
perl-DBD-MySQL-4.013-3.el6.x86_64
mysql-server-5.1.73-8.el6_8.x86_64
mysql-5.1.73-8.el6_8.x86_64

執行如下命令
yum remove mysql mysql-server mysql-libs compat-mysql51

rm -rf /var/lib/mysql

rm /etc/my.cnf

檢視是否還有mysql軟體：
rpm -qa|grep mysql

有的話繼續刪除，可能出現的：
mysql-libs-5.1.73-8.el6_8.x86_64
perl-DBD-MySQL-4.013-3.el6.x86_64
mysql-server-5.1.73-8.el6_8.x86_64
mysql-5.1.73-8.el6_8.x86_64
刪除方式：
rpm -e 包名（即：上面的四個）//普通刪除
rpm -e –nodeps 包名

檢視殘留的目錄：
whereis mysql
或者：find / -name mysql

/etc/rc.d/init.d/mysql
/etc/logrotate.d/mysql
/usr/local/Java/mysql
/usr/bin/mysql
/usr/share/mysql
/usr/include/mysql
/usr/include/mysql/mysql
/usr/lib64/mysql
/var/lock/subsys/mysql
/var/lib/mysql
/var/lib/mysql/mysql

然後刪除mysql目錄：rm -rf 目錄
最後執行whereis mysql
結果為：mysql：

解除安裝完成！

二：安裝

以rmp安裝包為例
下載地址： https://dev.mysql.com/downloads/mysql/5.6.html
MySQL-client-5.6.36-1.el6.x86_64.rpm
MySQL-devel-5.6.36-1.el6.x86_64.rpm
MySQL-server-5.6.36-1.el6.x86_64.rpm
1.安裝rpm包
rpm -ivh MySQL-client-5.6.36-1.el6.x86_64.rpm
rpm -ivh MySQL-devel-5.6.36-1.el6.x86_64.rpm
rpm -ivh MySQL-server-5.6.36-1.el6.x86_64.rpm
或者
rpm -ivh MySQL-*

由於電腦或其他一些原因導致使用簡化的安裝命令會導致安裝無法100%完成，只能逐個安裝

2.執行安裝語句：
[root @localhost opt]# rpm -ivh MySQL-*
Preparing… ########################################### [100%]
1:MySQL-server ########################################### [100%]
……………………………………………………………..
………………………省略中間過程…………………….
………………………………………………………………..
……………………….注意閱讀下面內容………………..

A RANDOM PASSWORD HAS BEEN SET FOR THE MySQL root USER !
You will find that password in ‘/root/.mysql_secret’.
You must change that password on your first connect,
no other statement but ‘SET PASSWORD’ will be accepted.
See the manual for the semantics of the ‘password expired’ flag.
Also, the account for the anonymous user has been removed.
In addition, you can run:
/usr/bin/mysql_secure_installation
which will also give you the option of removing the test database.
This is strongly recommended for production servers.
See the manual for more instructions.
Please report any problems at http://bugs.mysql.com/
The latest information about MySQL is available on the web at
http://www.mysql.com
Support MySQL by buying support/licenses at http://shop.mysql.com
New default config file was created as /usr/my.cnf and
will be used by default by the server when you start it.
You may edit this file to change server settings

3.複製配置檔案
cp /usr/share/mysql/my-default.cnf /etc/my.cnf

4.初始化mysql
/usr/bin/mysql_install_db

5.啟動mysql伺服器
service mysql start

結果一：
Staring MySQL .......SUCCESS!
結果二：
Starting MySQL Logging to ‘/var/lib/mysql/localhost.err’...
...........SUCCESS!

6.檢視當前執行狀態：
service mysql status

7.檢視初始密碼
cat /root/.mysql_secret

8.使用初始密碼進入mysql
mysql -uroot -p初始密碼

9.修改初始密碼（在mysql下）
set PASSWORD = PASSWORD(‘新密碼’)；
10.退出:
exit;

三、其他
1.設定開機啟動
chkconfig mysql on

2.優化/etc/my.cnf配置
①開啟my.cnf
vi /etc/my.cnf
②在配置檔案中編輯

[mysqld]
port    =   3306
default-storage-engine  =   InnoDB  
character_set_server=utf8   
character_set_client=utf8   
collation-server=utf8_general_ci    
lower_case_table_names=1    #表名大小寫：0--區分，1--不區分
max_connections=1000        #設定最大連線，允許最大連線為16384

[client]
password    =   root
port    =   3306
default-character-set=utf8  

[mysql]
default-character-set   =   utf8    

上述變數可能有不存在的導致登入時報錯，可檢視mysql日誌根據錯誤修改配置

應用此優化配置後執行：rpm –qa|grep -i mysql 的結果如下
[[email protected] ~]# rpm -qa|grep -i mysql
MySQL-server-5.6.36-1.el6.x86_64
MySQL-devel-5.6.36-1.el6.x86_64
MySQL-client-5.6.36-1.el6.x86_64

3.關閉mysql伺服器
service mysql stop

4.mysql預設安裝位置
/var/lib/mysql/ #資料庫目錄
/usr/share/mysql #配置檔案目錄
/usr/bin #相關命令目錄
/etc/init.d/mysql #啟動指令碼