Detailed tutorial on installing MySQL database in Linux environment (including uninstallation and password reset process)

This tutorial is for centos7/8,mysql 5.x

1、 uninstall mysql（ important ）

In the installation mysql Make sure you don't have... In your system before mysql, Even if you are a newly installed system or a newly purchased cloud service , You also need to check whether there is mysql Related documents , This is important ！（ Some images of Tencent cloud include by default mysql The file of ）, If it already exists before installation mysql Related documents , Will lead to subsequent mysql Installation failed .
Completely delete mysql step ：
（1） Use rpm Command to view installed packages
Enter the following command to check if mysql Software ：

rpm -qa | grep mysql

If you find the relevant documents , for example

Use rpm -e file name To delete the file , Take the above file as an example , Execute the following command ：

rpm -e mysql57-community-release-el7-10.noarch

Reuse rpm -e Command to delete files , Until all files are completely deleted
（2） Use yum Uninstall the installed mysql

yum remove mysql mysql-server mysql-libs mysql-server

（3） Search for mysql file
The global search name contains mysql All files for

find / -name '*mysql*'

Delete all the search results mysql file , If not installed mysql, Usually search out /var/lib/* and /usr/share/* These two directories contain mysql file . Delete file command ：

#  With  /var/lib/mysql  For example 
rm -rf /var/lib/mysql

Use rm -rf Command to delete all searched mysql file .

Linux Copy shortcut keys in ：ctrl + insert, Paste shortcut ：shift + insert Or use the middle mouse button

Finally, check again ：

#  Check 1
rpm -qa|grep mysql

#  Check 2
find / -name '*mysql*'

If any, continue to delete , Until it is deleted ！

2、 download mysql The installation files

Linux It is recommended to use RPM Package to install mysql.
download ：

wget http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm

rpm install ：

rpm -ivh mysql-community-release-el7-5.noarch.rpm

yum install mysql-server：

yum install -y mysql-server

If you don't have permission , You can execute the following command to set permissions （root The user does not need to execute ）：

chown -R mysql:mysql /var/lib/mysql/

Start the service ：

systemctl start mysqld.service

see mysql Running state ：

service mysqld status

Check the initial password ：

grep 'password' /var/log/mysqld.log

The initial password is marked in the red box , However, in some cases, the initial password cannot be queried , How to change the password will be said later .
Copy the initial password , Log in ：

mysql -u root -p

After typing the command , Click enter , Will let you enter the password , Then input the initial password just now （ It is not visible when inputting the password ）, Of course, paste is supported , You can copy the initial password after , Then paste . If there is no password , Just go back .

After logging in successfully, it will display ：

View all databases ：

Here we are ,mysql The database is installed .

3、 modify mysql password

In many cases , Need to change the initial password , But if you can't see the initial password in the previous steps , There is no way to log in to the database , Then you need to change the password . Let's take the inability to view the initial password as an example （ Or forget your login password ）, Briefly introduce the password modification process .
（1） Set skip login password
open mysql Configuration file for ：

vi /etc/my.cnf

Press... After opening the file a Key to enter edit mode , stay [mysqld] Add... Below the configuration skip-grant-tables, As shown in the figure below ：

Then press esc key , Input :wq Save the file .

（2） restart mysql service

service mysqld restart

（3） Get into mysql

mysql -u root -p

Press enter after entering the above command , Will skip password verification , Direct access to mysql in .

（4） Change user login password
Get into mysql library ：

use mysql

Change Password ：

update user set password=password(' The password you set ') where User='root' and Host='localhost';

Be careful ： Set up Host=‘localhost’ May cause the remote connection to fail ！

Update cache ：

flush privileges;

sign out mysql：

exit

（4） Restore profile
Re enter my.cnf Comment out the document skip-grant-tables, The effect is shown below

Press esc Key to exit edit mode , Input :wq Save the file .

Restart again mysql service ：

service mysqld restart

Then connect to the database , Enter your modified password to see if you can enter , If you can enter, it means that the password has been modified successfully , Otherwise, follow the steps again .