在Ubuntu中atp安装的mysql，默认数据目录在/var/lib/mysql ，添加了一块硬盘，需要将数据目录改为独立硬盘中。
修改mysql配置文件后重启报错，提示权限拒绝，修改了目录属主属组仍旧不行。

root@iZwz9g269i424nee31ly7yZ:/mysql/data# systemctl status mysql
● mysql.service - MySQL Community Server
     Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Sun 2024-04-07 17:14:53 CST; 10s ago
    Process: 891921 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
    Process: 891929 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
   Main PID: 891929 (code=exited, status=1/FAILURE)
     Status: "Server shutdown complete"
      Error: 13 (Permission denied)

Apr 07 17:14:53 iZwz9g269i424nee31ly7yZ systemd[1]: mysql.service: Scheduled restart job, restart counter is at 5.
Apr 07 17:14:53 iZwz9g269i424nee31ly7yZ systemd[1]: Stopped MySQL Community Server.
Apr 07 17:14:53 iZwz9g269i424nee31ly7yZ systemd[1]: mysql.service: Start request repeated too quickly.
Apr 07 17:14:53 iZwz9g269i424nee31ly7yZ systemd[1]: mysql.service: Failed with result 'exit-code'.
Apr 07 17:14:53 iZwz9g269i424nee31ly7yZ systemd[1]: Failed to start MySQL Community Server.

最终发现是apparmor这个服务导致的，apparmor是与selinux类似的访问控制机制。

root@iZwz9g269i424nee31ly7yZ:~# cat /etc/apparmor.d/usr.sbin.mysqld 
将
# Allow data dir access
  /var/lib/mysql/ r
  /var/lib/mysql/** rwk

改为
# Allow data dir access
  /mysql/data/ r,
  /mysql/data/** rwk,

# 重启apparmor及mysql
root@iZwz9g269i424nee31ly7yZ:~# /etc/init.d/apparmor restart
root@iZwz9g269i424nee31ly7yZ:~# systemctl restart mysql