Switching release channels

    Flatcar Container Linux is designed to be updated automatically with different schedules per channel. You can disable this feature , although we don’t recommend it. Read the release notes for specific features and bug fixes.

    By design, the Flatcar Container Linux update engine does not execute downgrades. If you’re switching from a channel with a higher Flatcar Container Linux version than the new channel, your machine won’t be updated again until the new channel contains a higher version number.

    Update Timeline

    Customizing channel configuration

    The update engine sources its configuration from /usr/share/flatcar/update.conf and /etc/flatcar/update.conf. The former file contains the default hardcoded configuration from the running OS version. Its values cannot be edited, but they can be overridden by the ones in the latter file.

    To switch a machine to a different channel, specify the new channel group in /etc/flatcar/update.conf:

    GROUP=beta
    

    In order for the configuration override to take effect, the update engine must first be restarted:

    sudo systemctl restart update-engine
    

    Debugging

    After the update engine is restarted, the machine should check for an update within an hour.

    The live status of updates checking can queried via:

    update_engine_client --status
    

    The update engine logs all update attempts, which can inspected in the system journal:

    journalctl -f -u update-engine
    

    For reference, the OS version and channel for a running system can be determined via:

    cat /usr/share/flatcar/os-release
    cat /usr/share/flatcar/update.conf
    

    Note: while a manual channel switch is in progress, /usr/share/flatcar/update.conf shows the channel for the current OS while /etc/flatcar/update.conf shows the one for the next update.