Recently fiddledDocker, I found some problems that have not been encountered in the virtual machine, and now record them. If there are many problems encountered in the future, they may be integrated into a series and then classified
inDocker ContainerCentos 8 Open the firewall service in the mirror, execute the commandsystemctl start firewalldTimes error

System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down

As shown below:

The Chinese meaning of the error message is:

The systemd has not been used as the initialization system (PID 1) to boot the system. Unable to operate.
 Unable to connect to the bus: host is down

CheckOfficial document

the reasonIt roughly means:Docker The container is by defaultRun as "unprivileged",in"Non-privileged"underDo not allow containers to access any devices, The access of the container to the host is different from the process running outside the container on the host. Only after "privilege"At runtime, onlyAllow container to access any deviceAnd can be inAppArmor OrSELinux Make some configuration in the host, allowing the container to access the host almost the same as the process running outside the container on the host.

solution:
Use "privilege"Run, the specific steps are as follows:

• First, to save the current container as a new image, use the commanddocker commit container ID image name
  
  As shown in the figure above, set the container ID to98 starts Save the container to the new imagemy-centos in
• Create another one with "privilege"Run the virtual terminal (container), use the command

docker run -itd   --privileged=true --name New container name New image name /usr/sbin/init #Use the mirror "my-centos" to run the container named "my_centos" interactively in the background with "privileged" to execute the "/usr/sbin/init" command and return the ID of the container

As shown below:

Use commandsdocker ps -aView all containers on this machine, you can see that there is already amy_centos The container

• Enter the container and use the commanddocker exec -it my_centos /bin/bashUse the container name to enter here, you can also use the commanddocker exec -it container ID /bin/bashenter
  
  As can be seen from the above figure, it has successfully entered the container and used the commandls ./Check the file to find out before98 starts The contents of the container are consistent
• Enter againmy_centos In the container and executesystemctl start firewalldcommand
  
  As you can see from the picture above, no more errors are reported