CentOS 7 installs Mysql and sets the method to boot from startup

CentOS 7 no longer has an Mysql database; the default database is MariaDB (a branch of Mysql).

You can manually install the Mysql database by following these steps.

1. Download the rpm installation file

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

2. Perform the rpm installation

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

When dependency resolution is complete, the following options appear:

Dependencies Resolved

==============================================================================================================
 Package             Arch     Version     Repository       Size
==============================================================================================================
Installing:
 mysql-community-libs         x86_64    5.6.32-2.el7    mysql56-community     2.0 M
 replacing mariadb-libs.x86_64 1:5.5.47-1.el7_2
 mysql-community-server         x86_64    5.6.32-2.el7    mysql56-community      59 M
 Installing for dependencies:
 mysql-community-client         x86_64    5.6.32-2.el7    mysql56-community      19 M
 mysql-community-common         x86_64    5.6.32-2.el7    mysql56-community     256 k
 perl-Compress-Raw-Bzip2         x86_64    2.061-3.el7    base         32 k
 perl-Compress-Raw-Zlib         x86_64    1:2.061-4.el7   base         57 k
 perl-DBI            x86_64    1.627-4.el7    base         802 k
 perl-IO-Compress          noarch    2.061-2.el7    base         260 k
 perl-Net-Daemon           noarch    0.48-5.el7    base         51 k
 perl-PlRPC            noarch    0.2020-14.el7   base         36 k

Transaction Summary
=============================================================================================================
Install 2 Packages (+8 Dependent packages)

Total download size: 82 M
Is this ok [y/d/N]:

3. As you can see, both server and client have been selected for installation. Select y to download and install automatically.

4. When the installation is complete, start Mysql.

systemctl start mysqld.service

5. Set the root password.

update user set password=password("123456") where user='root';

6. Start from startup.

vim /etc/rc.local
 add service mysqld start

7. Important updates:

The new rpm installation file does not have the script for the automatic yum installation, so you need to manually perform the yum installation.

After step 2, just execute yum install mysql-server.

8. About self-starting

Step 6 only applies if mysqld is not self-booting.

If mysql is self-booted by default, there may be problems with the self-booting in rc.local such as out-of-order.

A more secure solution is as follows:

Problem with CentOS 7 program startup

1. Problem phenomena:

After system restart, it was found that the mysqld service started normally, but the application A, which relies on the mysql database, failed to start.

Viewing the log shows that the program A failed to connect to the database when it started.

2. Reason analysis:

The mysqld service started normally.

At this point, manually restart the program A, and A is also running normally.

Conclusion: this means that when the program A is started, mysqld may not be started.

3. Startup sequence

The first thing that came to mind was tweaking the startup order of the mysqld service to make it higher than my application A.

However, no startup script for mysqld was found under the /etc/ init.d path.

4. Work your way through

The mysqld installation that follows the link is automatically started by default.

You can unboot mysqld and write a startup script to make sure it starts before A starts.

5. Solutions

1. View the system's current default method of starting a project, not setup or something like that.

systemctl list-unit-files

Execute this command to view the current system's service startup and service status.

The results are as follows:

 ...
 microcode.service       enabled 
 mysql.service        enabled 
 mysqld.service        enabled 
 NetworkManager-dispatcher.service   enabled 
 ...

2. Cancel the self-booting of mysqld

systemctl disable mysqld

After executing this command, check the service status of the current system:

 ...
 microcode.service       enabled 
 mysqld.service        disabled
 NetworkManager-dispatcher.service   enabled 
 ...

3. Custom /etc/ rc.local

First, execute systemctl start mysqld

Perform startA