启动一个docker容器：

snippet.bash

[yz@test-4 ~]$ sudo docker run --privileged=true --name ff_1 -itd centos:build8 /bin/bash
ff02aed2db53……

在docker里无法使用systemctl：

snippet.bash

[yz@test-4 ~]$ sudo docker attach ff02aed2db53
 
[yz@ff02aed2db53 ~]$ 
[yz@ff02aed2db53 ~]$ sudo systemctl start cgconfig.service
Failed to get D-Bus connection: Operation not permitted

docker run命令作两项修改：

• /bin/bash → /usr/sbin/init
• 增加 -u root 参数

snippet.bash

[yz@test-4 ~]$ sudo docker run --privileged=true -u root --name ff_2 -itd centos:build8 /usr/sbin/init
ea6f89d980……
[yz@test-4 ~]$ sudo docker exec -it ff_2 /bin/bash
 
[root@ea6f89d9804d ~]# systemctl start cgconfig.service
[root@ea6f89d9804d ~]# systemctl status cgconfig.service
● cgconfig.service - Control Group configuration service
   Loaded: loaded (/usr/lib/systemd/system/cgconfig.service; disabled; vendor preset: disabled)
   Active: active (exited) since Thu 2020-10-28 01:13:44 UTC; 2s ago
  Process: 577 ExecStart=/usr/sbin/cgconfigparser -l /etc/cgconfig.conf -L /etc/cgconfig.d -s 1664 (code=exited, status=0/SUCCESS)
 Main PID: 577 (code=exited, status=0/SUCCESS)
 
Oct 28 01:13:44 ea6f89d9804d systemd[1]: Starting Control Group configuration service...
Oct 28 01:13:44 ea6f89d9804d systemd[1]: Started Control Group configuration service.

如果希望加入docker时使用指定用户而不是root用户，则：

snippet.bash

[yz@test-4 ~]$ sudo docker exec -u yz -it ff_2 /bin/bash
[yz@ea6f89d9804d ~]$