Ubuntu 20.04安装mysql-server失败求助：服务启动报错

问题场景 #

在Ubuntu 20.04环境下安装mysql-server时出现服务启动失败问题，已尝试以下清理命令后重新安装，故障依旧：

sudo apt-get purge mysql*
sudo apt-get autoremove
sudo apt-get autoclean
sudo apt-get dist-upgrade
sudo apt-get install mysql-server

安装过程核心报错信息：

Setting up mysql-server-8.0 (8.0.31-0ubuntu0.20.04.1) ...
Renaming removed key_buffer and myisam-recover options (if present)
Warning: Unable to start the server.
Job for mysql.service failed because the control process exited with error code.
...
Process: 3897 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
...
dpkg: error processing package mysql-server-8.0 (--configure):
 installed mysql-server-8.0 package post-installation script subprocess returned error exit status 1
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-8.0; however:
  Package mysql-server-8.0 is not configured yet.

E: Sub-process /usr/bin/dpkg returned an error code (1)

解决方案 #

1. 彻底清理MySQL全量残留文件 #

常规purge命令可能遗漏部分配置或数据文件，执行以下命令彻底移除所有MySQL相关组件与残留：

sudo apt-get purge mysql-server mysql-server-8.0 mysql-client mysql-client-8.0 mysql-common mysql-server-core-8.0 mysql-client-core-8.0
sudo apt-get autoremove --purge
sudo apt-get autoclean
# 删除残留的配置、数据、日志目录
sudo rm -rf /etc/mysql /var/lib/mysql /var/log/mysql
# 删除MySQL相关用户与用户组
sudo deluser mysql
sudo delgroup mysql

2. 修复系统依赖与dpkg状态 #

清理完成后，修复系统依赖并重置dpkg的损坏状态：

sudo apt-get update
sudo apt-get -f install
sudo dpkg --configure -a

3. 重新安装MySQL-Server #

完成上述步骤后，重新执行安装命令：

sudo apt-get install mysql-server

4. 手动校验服务状态与权限 #

安装完成后手动启动服务并检查运行状态：

sudo systemctl start mysql.service
sudo systemctl status mysql.service

若仍启动失败，查看详细日志定位问题：

journalctl -u mysql.service -xe

常见故障点为/var/lib/mysql目录权限异常，可执行以下命令修复：

sudo chown -R mysql:mysql /var/lib/mysql
sudo chmod -R 755 /var/lib/mysql
sudo systemctl restart mysql.service

5. 处理AppArmor权限限制（可选） #

如果日志显示AppArmor相关权限报错，刷新规则后重启服务：

sudo apparmor_parser -r /etc/apparmor.d/usr.sbin.mysqld
sudo systemctl restart mysql.service

内容的提问来源于stack exchange，提问作者Liton Mazumder