本次將在Linux下通過yum安裝MySQL，安裝的版本為MySQL 5.7，官網中是最新版本8.0，在網上查了下，發現最新版本的yum源也包含了舊版本，而我們，只需要在安裝時啟用 5.7 的安裝即可。
本人環境：CentOS 7.3 64位
- 1.檢查CentOS是否有系統自帶的mysql
yum list installed | grep mysql
如果存在系統自帶的mysql及依賴，則通過 yum remove 將其卸載
- 2.在官網中獲取yum源
這里獲取到的是最新版本的下載地址：https://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm
- 3.CentOS中下載rpm包，並安裝本地mysql源
下載rpm包：wget https://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm --no-check-certificate
安裝mysql源：yum localinstall mysql80-community-release-el7-3.noarch.rpm
通過 yum localinstall 安裝mysql源，可以幫助我們解決本地rpm包的依賴問題。
最后，驗證是否安裝成功：yum repolist all | grep mysql
- 4.修改默認安裝版本為5.7
從上面的圖片，我們可以看到，默認是MySQL 8.0可用，我們若想安裝MySQL 5.7，則需啟用5.7。接下來通過直接修改配置文件來設置啟用。
vim /etc/yum.repos.d/mysql-community.repo
輸入上面的命令，在編輯界面，先輸入 i 進入編輯模式，將8.0的 enabled 設置為0，將5.7的 enabled 設置為1，如下：
接着按 Esc 退出編輯模式，最后輸入 :wq 保存並退出。
再次輸入命令：yum repolist all | grep mysql ，可以看到8.0已被禁用，而5.7是啟用的。
- 5.安裝MySQL
yum install mysql-community-server
輸入上面命令，進行安裝即可。
[root@wintest mysql]# yum install mysql-community-server
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package mysql-community-server.x86_64 0:5.7.27-1.el7 will be installed
--> Processing Dependency: mysql-community-common(x86-64) = 5.7.27-1.el7 for package: mysql-community-server-5.7.27-1.el7.x86_64
--> Processing Dependency: mysql-community-client(x86-64) >= 5.7.9 for package: mysql-community-server-5.7.27-1.el7.x86_64
--> Processing Dependency: libaio.so.1(LIBAIO_0.4)(64bit) for package: mysql-community-server-5.7.27-1.el7.x86_64
--> Processing Dependency: libaio.so.1(LIBAIO_0.1)(64bit) for package: mysql-community-server-5.7.27-1.el7.x86_64
--> Processing Dependency: libaio.so.1()(64bit) for package: mysql-community-server-5.7.27-1.el7.x86_64
--> Running transaction check
---> Package libaio.x86_64 0:0.3.109-13.el7 will be installed
---> Package mysql-community-client.x86_64 0:5.7.27-1.el7 will be installed
--> Processing Dependency: mysql-community-libs(x86-64) >= 5.7.9 for package: mysql-community-client-5.7.27-1.el7.x86_64
---> Package mysql-community-common.x86_64 0:5.7.27-1.el7 will be installed
--> Running transaction check
---> Package mariadb-libs.x86_64 1:5.5.52-1.el7 will be obsoleted
--> 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
---> Package mysql-community-libs.x86_64 0:5.7.27-1.el7 will be obsoleting
--> Running transaction check
---> Package mysql-community-libs-compat.x86_64 0:5.7.27-1.el7 will be obsoleting
---> Package postfix.x86_64 2:2.10.1-6.el7 will be updated
---> Package postfix.x86_64 2:2.10.1-7.el7 will be an update
--> Finished Dependency Resolution
Dependencies Resolved
====================================================================================
Package Arch Version Repository Size
====================================================================================
Installing:
mysql-community-libs x86_64 5.7.27-1.el7 mysql57-community 2.2 M
replacing mariadb-libs.x86_64 1:5.5.52-1.el7
mysql-community-libs-compat x86_64 5.7.27-1.el7 mysql57-community 2.0 M
replacing mariadb-libs.x86_64 1:5.5.52-1.el7
mysql-community-server x86_64 5.7.27-1.el7 mysql57-community 165 M
Installing for dependencies:
libaio x86_64 0.3.109-13.el7 base 24 k
mysql-community-client x86_64 5.7.27-1.el7 mysql57-community 24 M
mysql-community-common x86_64 5.7.27-1.el7 mysql57-community 275 k
Updating for dependencies:
postfix x86_64 2:2.10.1-7.el7 base 2.4 M
Transaction Summary
====================================================================================
Install 3 Packages (+3 Dependent packages)
Upgrade ( 1 Dependent package)
Total download size: 197 M
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
(1/7): libaio-0.3.109-13.el7.x86_64.rpm | 24 kB 00:00:00
warning: /var/cache/yum/x86_64/7/mysql57-community/packages/mysql-community-common-5.7.27-1.el7.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 5072e1f5: NOKEY
Public key for mysql-community-common-5.7.27-1.el7.x86_64.rpm is not installed
(2/7): mysql-community-common-5.7.27-1.el7.x86_64.rpm | 275 kB 00:00:01
(3/7): mysql-community-libs-5.7.27-1.el7.x86_64.rpm | 2.2 MB 00:00:01
(4/7): mysql-community-libs-compat-5.7.27-1.el7.x86_64.rpm | 2.0 MB 00:00:01
(5/7): postfix-2.10.1-7.el7.x86_64.rpm | 2.4 MB 00:00:00
(6/7): mysql-community-client-5.7.27-1.el7.x86_64.rpm | 24 MB 00:00:34
(7/7): mysql-community-server-5.7.27-1.el7.x86_64.rpm | 165 MB 00:00:52
------------------------------------------------------------------------------------
Total 3.5 MB/s | 197 MB 00:56
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
Importing GPG key 0x5072E1F5:
Userid : "MySQL Release Engineering <mysql-build@oss.oracle.com>"
Fingerprint: a4a9 4068 76fc bd3c 4567 70c8 8c71 8d3b 5072 e1f5
Package : mysql80-community-release-el7-3.noarch (installed)
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
Is this ok [y/N]: y
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : mysql-community-common-5.7.27-1.el7.x86_64 1/9
Installing : mysql-community-libs-5.7.27-1.el7.x86_64 2/9
Installing : mysql-community-libs-compat-5.7.27-1.el7.x86_64 3/9
Installing : mysql-community-client-5.7.27-1.el7.x86_64 4/9
Installing : libaio-0.3.109-13.el7.x86_64 5/9
Installing : mysql-community-server-5.7.27-1.el7.x86_64 6/9
Updating : 2:postfix-2.10.1-7.el7.x86_64 7/9
Cleanup : 2:postfix-2.10.1-6.el7.x86_64 8/9
Erasing : 1:mariadb-libs-5.5.52-1.el7.x86_64 9/9
Verifying : mysql-community-libs-compat-5.7.27-1.el7.x86_64 1/9
Verifying : mysql-community-common-5.7.27-1.el7.x86_64 2/9
Verifying : mysql-community-libs-5.7.27-1.el7.x86_64 3/9
Verifying : 2:postfix-2.10.1-7.el7.x86_64 4/9
Verifying : mysql-community-server-5.7.27-1.el7.x86_64 5/9
Verifying : mysql-community-client-5.7.27-1.el7.x86_64 6/9
Verifying : libaio-0.3.109-13.el7.x86_64 7/9
Verifying : 1:mariadb-libs-5.5.52-1.el7.x86_64 8/9
Verifying : 2:postfix-2.10.1-6.el7.x86_64 9/9
Installed:
mysql-community-libs.x86_64 0:5.7.27-1.el7
mysql-community-libs-compat.x86_64 0:5.7.27-1.el7
mysql-community-server.x86_64 0:5.7.27-1.el7
Dependency Installed:
libaio.x86_64 0:0.3.109-13.el7
mysql-community-client.x86_64 0:5.7.27-1.el7
mysql-community-common.x86_64 0:5.7.27-1.el7
Dependency Updated:
postfix.x86_64 2:2.10.1-7.el7
Replaced:
mariadb-libs.x86_64 1:5.5.52-1.el7
Complete!
- 6.啟用MySQL
在CentOS 6中，我們一般通過 service mysqld start 來啟動mysql，在CentOS 7中，如果直接輸入 service mysqld start ，則會出現以下信息：
這是因為 CentOS 7 下重啟服務不再通過 service 操作，而是通過 systemctl 操作，因此我們可以輸入命令：
啟動mysql：systemctl start mysqld.service
查看mysql狀態：systemctl status mysqld.service
- 7.登錄mysql
mysql -u root -p
在要求輸入密碼時，因為mysql 5.7的初始密碼不是空，直接按回車鍵不能成功登錄，因此需先找到初始密碼，才能登錄。
grep 'temporary password' /var/log/mysqld.log
如上，最后的內容就是初始密碼。
再次登錄，輸入初始密碼，即可成功登錄。
第一次登錄成功后，發現不能執行操作，同時提示讓修改密碼。
- 8.修改登錄密碼
alter user root@localhost identified by '新密碼'
這里，我想設置新密碼為 123456，但出現了報錯，這里的報錯是mysql的密碼策略問題，輸入命令：show variables like 'validate_password%'，查看 mysql 初始的密碼策略，發現密碼的最小長度為8，密碼的驗證強度等級為MEDIUM，可以修改一下密碼策略：
設置密碼的驗證強度等級：set global validate_password_policy=LOW
設置密碼的最小長度：set global validate_password_length=6
好了，這時我們再次執行修改密碼的sql，便不會報錯了。
最后通過 flush privileges 刷新權限，使當前操作立即生效，就大功告成了。
注意：最后這里，也可以不修改密碼策略，只要自己設置的密碼滿足MySQL的原密碼策略即可。