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Prioritizing service order

Although systemd can start services in parallel, you can optimize service ordering by adjusting the dependency parameters in service unit files so that certain services will wait on other services to start before loading themselves. In this procedure, for example, you will create Quadlet unit files for the engine and radio services to configure their respective boot order.

Prerequisites

Procedure

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

    engine.container file
    [Unit]
Description=Demo engine service container
# routingmanagerd.socket is not included in vsomeip3 3.5.11, so let's use routingmanagerd.service for now
Requires=routingmanagerd.service
After=routingmanagerd.service

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

[Service]
Restart=always

[Install]
WantedBy=multi-user.target

    Note

    Requires=routingmanagerd.service is a hard dependency that prevents the engine service from starting until the routing manager service is active. After=routingmanagerd.service is an ordering dependency: the engine service starts only after the routing manager service has started.

    radio.socket file
    [Unit]
Description=example systemd unix socket

[Socket]
ListenStream=%t/root-ipc-demo/root_ipc.socket
RuntimeDirectory=root-ipc-demo

[Install]
WantedBy=sockets.target
    radio.container file
    [Unit]
Description=Demo radio service container
# routingmanagerd.socket is not included in vsomeip3 3.5.11, so let's use routingmanagerd.service for now
Requires=routingmanagerd.service
After=routingmanagerd.service
Requires=radio.socket
After=radio.socket
Wants=engine.service

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

[Service]
Restart=always

[Install]
WantedBy=multi-user.target

    Note

    Requires=radio.socket is a hard dependency that prevents the radio service from starting until the socket unit is active. After=radio.socket is an ordering dependency: the radio service starts only after the socket unit has started. Requires=routingmanagerd.service is a hard dependency that prevents the radio service from starting until the routing manager service is active. Wants=engine.service is a soft dependency. Ideally, the engine service activates the radio service, but if the engine service is not activated, systemd still permits the radio service to start.

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

    Manifest configuration to copy Quadlet unit files
    # root-root IPC communications demo

name: root-root-IPC-communications

content:
  repos:
    - id: epel
      metalink: https://mirrors.fedoraproject.org/metalink?repo=epel-10&arch=$arch

  rpms:
    - podman
    - netavark
    - aardvark-dns
    - 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
    - path: /etc/systemd/system/radio.socket
      source_path: ./radio.socket

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

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 aib-dev build to build a disk image:

    $ aib-dev build \
--distro autosd10 \
--target qemu \
--build-dir=_build \
root-root.aib.yml \
root-root.qcow2

  4. Verify that the script has created an AutoSD image file named root-root.qcow2 in your present working directory.

  5. Run the image:

    $ air --nographics root-root.qcow2

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

  7. From the VM, confirm the engine service started:

    # systemctl status engine.service
● engine.service - Demo engine service container
    Loaded: loaded (/etc/containers/systemd/engine.container; generated)
    Active: active (running) since Mon 2025-09-08 19:40:33 UTC; 7min ago
...

  8. List the dependencies for the engine service. The solid dot (●) to the left of routingmanagerd.service indicates that the service, which engine.service requires to start, is active:

    # systemctl list-dependencies engine.service
engine.service
● ├─routingmanagerd.service
● ├─system.slice
● ├─network-online.target
○ │ └─NetworkManager-wait-online.service
● └─sysinit.target
...

  9. Confirm the radio service started:

    # systemctl status radio.service
● radio.service - Demo radio service container
    Loaded: loaded (/etc/containers/systemd/radio.container; generated)
    Active: active (running) since Mon 2025-09-08 19:40:33 UTC; 28s ago
 ...

  10. List the dependencies for the radio service. The solid dot (●) to the left of engine.service indicates that the engine service is active:

    # systemctl list-dependencies radio.service
radio.service
● ├─engine.service
● ├─routingmanagerd.service
● ├─system.slice
● ├─network-online.target
○ │ └─NetworkManager-wait-online.service
● └─sysinit.target
...

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