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Running containers from systemd

When you embed a container in an operating system (OS) image, you can start the container manually in the booted system with the podman run command. However, the container does not start automatically at boot time. To configure a container to start at boot time, you must create a systemd service that starts the container at the right time, in the right way.

Quadlet is a tool that optimally runs Podman containers under systemd. Rather than creating the systemd service manually, use Quadlet to automatically generate the corresponding systemd service unit file at boot time. Quadlet simplifies container management by allowing you to create declarative configurations in .container files instead of lengthy, complex systemd unit files.

Quadlet unit files configure containers in both the root and QM partitions. In the AutoSD OS filesystem, store your .container files in /etc/containers/systemd.

At a minimum, include the following sections and options in a .container file:

[Unit]
Description=<A human-readable title>

[Container]
Image=<The container image>
Exec=<The command that runs in the container>

[Install]
WantedBy=multi-user.target default.target

Include additional sections and options to meet your container requirements. Any section or option permitted in a systemd.unit file is also permitted in a Quadlet unit file.

Containers within containers

The QM partition is a container within the root partition of an AutoSD OS image. The QM partition houses containers that run non-critical application workloads.

To add containers to the QM partition, you create Quadlet unit files and add them to the add_files section of your Automotive Image Builder manifest, for example:

Quadlet unit file added to an Automotive Image Builder manifest
    qm:
      content:
    ...
        add_files:
          - path: /etc/containers/systemd/ipc_client.container
            source_path: ./ipc_client.container

The example shows an ipc_client.container unit file added to the add_files section of the qm partition. The path section is the location for all container files, /etc/containers/systemd.

You can also create Quadlet unit files directly in the manifest, for example:

Quadlet unit file created in the Automotive Image Builder manifest
    qm:
    ...
      content:
    ...
        add_files:
          - path: /etc/containers/systemd/nginx.container
            text: |
              [Container]
              Image=localhost/nginx
              PublishPort=8080:80

              [Install]
              WantedBy=multi-user.target

The example shows an nginx container image created directly from the manifest. The text section contains the contents of the .container file.

Configuring communication between QM containers demonstrates additional Quadlet unit file use cases.

Creating Quadlet files for sample applications

In this example, create Quadlet files for the sample applications that are available in the AutoSD sample-images/files repository. If you want to use your own containerized software, see the Podman documentation for more information about creating your own Quadlet configuration files.

Prerequisites

Procedure

  1. Create Quadlet unit files for the radio-service and engine-service services in your sample application auto-apps:

    radio.container file
    [Unit]
Description=Demo radio service container
Requires=routingmanagerd.socket
After=routingmanagerd.socket
Wants=engine.service

[Container]
Image=localhost/auto-apps
Exec=/usr/bin/radio-service
Volume=/run/vsomeip:/run/vsomeip

[Service]
Restart=always

[Install]
WantedBy=multi-user.target
    engine.container file
    [Unit]
Description=Demo engine service container
Requires=routingmanagerd.socket
After=routingmanagerd.socket

[Container]
Image=localhost/auto-apps
Exec=/usr/bin/engine-service
Volume=/run/vsomeip:/run/vsomeip

[Service]
Restart=always

[Install]
WantedBy=multi-user.target

  2. Create an Automotive Image Builder manifest named quadlet_radio_engine.aib.yml that contains the following code, which copies the Quadlet unit files to the /etc/containers/systemd/ directory during the OS image build process:

    Manifest configuration to copy Quadlet unit files
    # Example manifest building an image with, pre-installed, a container image
# hosted in a remote container registry

name: quadlet_radio_engine

content:
  repos:
    - id: copr-sample-apps
      baseurl: https://download.copr.fedorainfracloud.org/results/alexl/cs9-sample-images/centos-stream-9-$arch/
  rpms:
    - podman
    - containernetworking-plugins
    - vsomeip3-routingmanager
    - dlt-daemon
    # For testing the image only:
    - openssh-server
    - openssh-clients

  container_images:
    # Get the auto-apps container image from gitlab
    - source: registry.gitlab.com/centos/automotive/sample-images/demo/auto-apps
      tag: latest
      name: localhost/auto-apps

  add_files:
    - path: /etc/containers/systemd/radio.container
      source_path: ../radio.container
    - path: /etc/containers/systemd/engine.container
      source_path: ../engine.container

  # Required for testing the image only:
  systemd:
    enabled_services:
      # Enable ssh daemon
      - sshd.service
      # Enable the dlt daemon
      - dlt

auth:
  # "password"
  root_password: $6$xoLqEUz0cGGJRx01$H3H/bFm0myJPULNMtbSsOFd/2BnHqHkMD92Sfxd.EKM9hXTWSmELG8cf205l6dktomuTcgKGGtGDgtvHVXSWU.
  # Required for testing the image only:
  sshd_config:
    PasswordAuthentication: true
    PermitRootLogin: true

    Note

    The path: option resolves a relative path. In this example, your Quadlet unit files are in the ../ directory.

  3. Run the automotive-image-builder tool to build an OS image:

    $ sudo automotive-image-builder \
    --verbose --container \
    --include=/var/lib/containers/storage/ \
    build \
    --distro autosd9 \
    --target qemu \
    --mode image \
    --build-dir=_build \
    --export qcow2 \
    quadlet_radio_engine.aib.yml \
    quadlet_radio_engine.$arch.qcow2

  4. Verify that the script has created an AutoSD image file named quadlet_radio_engine.<arch>.qcow2 in your present working directory.

  5. Assuming that you have installed QEMU, boot the AutoSD image in a virtual machine, substituting the name of your .qcow2 image file (if necessary):

    $ sudo automotive-image-runner quadlet_radio_engine.x86_64.qcow2

  6. After the image boots in QEMU, log in with the user name root and the password password.

Additional resources

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