Overview of systemctl

    systemctl is your interface to systemd, the init system used in Flatcar Container Linux. All processes on a single machine are started and managed by systemd, including your Docker containers. You can learn more in our Getting Started with systemd guide. Let’s explore a few helpful systemctl commands. You must run all of these commands locally on the Flatcar Container Linux machine:

    Find the status of a container

    The first step to troubleshooting with systemctl is to find the status of the item in question. If you have multiple Exec commands in your service file, you can see which one of them is failing and view the exit code. Here’s a failing service that starts a private Docker registry in a container:

    $ sudo systemctl status custom-registry.service
    custom-registry.service - Custom Registry Service
       Loaded: loaded (/media/state/units/custom-registry.service; enabled-runtime)
       Active: failed (Result: exit-code) since Sun 2013-12-22 12:40:11 UTC; 35s ago
      Process: 10191 ExecStopPost=/usr/bin/etcdctl delete /registry (code=exited, status=0/SUCCESS)
      Process: 10172 ExecStartPost=/usr/bin/etcdctl set /registry index.domain.com:5000 (code=exited, status=0/SUCCESS)
      Process: 10171 ExecStart=/usr/bin/docker run -rm -p 5555:5000 /bin/sh /root/boot.sh (code=exited, status=1/FAILURE)
     Main PID: 10171 (code=exited, status=1/FAILURE)
       CGroup: /system.slice/custom-registry.service
    Dec 22 12:40:01 localhost etcdctl[10172]: index.domain.com:5000
    Dec 22 12:40:01 localhost systemd[1]: Started Custom Registry Service.
    Dec 22 12:40:01 localhost docker[10171]: Unable to find image '' (tag: latest) locally
    Dec 22 12:40:11 localhost docker[10171]: 2013/12/22 12:40:11 Invalid Registry endpoint: Get http://index2.domain.com:5000/v1/_ping: dial tcp timeout
    Dec 22 12:40:11 localhost systemd[1]: custom-registry.service: main process exited, code=exited, status=1/FAILURE
    Dec 22 12:40:11 localhost etcdctl[10191]: index.domain.com:5000
    Dec 22 12:40:11 localhost systemd[1]: Unit custom-registry.service entered failed state.
    Hint: Some lines were ellipsized, use -l to show in full.

    You can see that Process: 10171 ExecStart=/usr/bin/docker exited with status=1/FAILURE and the log states that the index that we attempted to launch the container from, wasn’t valid, so the container image couldn’t be downloaded.

    List status of all units

    Listing all of the processes running on the box is too much information, but you can pipe the output into grep to find the services you’re looking for. Here’s all service files and their status:

    sudo systemctl list-units | grep .service

    Start or stop a service

    sudo systemctl start apache.service
    sudo systemctl stop apache.service

    Kill a service

    This will stop the process immediately:

    sudo systemctl kill apache.service

    Restart a service

    Restarting a service is as easy as:

    sudo systemctl restart apache.service

    If you’re restarting a service after you changed its service file, you will need to reload all of the service files before your changes take effect:

    sudo systemctl daemon-reload

    More information