MySQL安装记录
首先是卸载问题：如果安装 mysql 错误，请按如下标准卸载：
# 关闭mysql服务
sudo service stop mysql；
# 清除所有mysql包
sudo apt purge mysql-server mysql-client mysql-common mysql-server-core-* mysql-client-core-*
# 删除所有mysql文件
sudo rm -rf /etc/mysql /var/lib/mysql /var/log/mysql
# 最后清理所有不需要的包
sudo apt autoremove
sudo apt autoclean找不到 /var/run/mysqld/mysqld.sock 报错
如果启动 mysql 时遇到 Error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)，请仔细确认安装时是否有报错信息，根据报错原因去解决问题。
这类问题主要是my.cnf的配置指向错误，网上解决办法有很多种，请自行选择。
我自己遇到的是安装时提示 mysql-server depends on mysql-server-8.0，因为我是直接安装的 mysq-server，卸载重装时将安装包改为 mysql-server-8.0 就好了。
apt install -y mysql-server-8.0 mysql-common初始化mysql
在使用 mysql 前，先使用 mysql_secure_installation 初始化数据库。
初始化数据库遇到
# Failed! Error: SET PASSWORD has no significance for user ‘root’@’localhost’ as the authentication method used doesn’t store authentication data in the MySQL server, 先退出进程，直接mysql进入数据库，运行ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password by 'mynewpassword';’更改身份验证参数，然后重新初始化。（密码为 mynewpassword）
附上初始化过程：
root@6f72ddf70108:/# mysql_secure_installation
Securing the MySQL server deployment.
Enter password for user root:
The 'validate_password' component is installed on the server.
The subsequent steps will run with the existing configuration
of the component.
Using existing password for root.
Estimated strength of the password: 50
Change the password for root ? ((Press y|Y for Yes, any other key for No) : y
New password:
Re-enter new password:
Estimated strength of the password: 0
Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : y
... Failed! Error: Your password does not satisfy the current policy requirements
New password:
Re-enter new password:
Sorry, passwords do not match.
New password:
Re-enter new password:
Estimated strength of the password: 50
Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : y
By default, a MySQL installation has an anonymous user,
allowing anyone to log into MySQL 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? (Press y|Y for Yes, any other key for No) : 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? (Press y|Y for Yes, any other key for No) : n
... skipping.
By default, MySQL 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? (Press y|Y for Yes, any other key for No) : 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? (Press y|Y for Yes, any other key for No) : y
Success.
All done! mysql 启动失败：su: warning: cannot change directory to /nonexistent: No such file or directory
sudo service mysql stop
sudo usermod -d /var/lib/mysql/ mysql
sudo service mysql start