Webarchitects systemd Ansible role

systemd is a System and Service Manager that "runs as PID 1 and starts the rest of the system".

This repo contains an Ansible role for configuring systemd on Debian, this role has been designed to be as generic as possible in order to enable to it be used to configure any systemd service.

On Debian Buster and Bullseye when the backports repo is enabled this role will install systemd from backports, the Webarchitects apt Ansible role can be used to enable backports.

Role variables

See the defaults/main.yml file for the default variables and meta/argument_specs.yml for the variable specification.

systemd

Set the systemd variable to false to prevent any tasks in this role being run.

The systemd variable defaults to true.

systemd_delete_broken_symlinks

The systemd_delete_broken_symlinks variable is a boolean, when true is results in this role deleting broken symlinks found in the /etc/systemd directory, it defaults to false.

systemd_delete_devnull_symlinks

The systemd_delete_devnull_symlinks variable is a boolean, when true is results in this role deleting symlinks that point to /dev/null in the /etc/systemd directory, it defaults to false.

systemd_timesyncd_reboot

The systemd_timesyncd_reboot variable is a boolean, when true servers which have incorrect clocks will be rebooted by this role in an attempt to correct their clocks, it defaults to false.

This variable is only used if there is a item in the systemd_units list with the name systemd-timesyncd.

systemd_tz

The systemd_tz variable is a string for the time zone to be used when configuring systemd-timesyncd, (the hardware clock is set to UTC), it defaults to Etc/UTC, which is fine for a server however for a desktop or laptop you will want to use a value like Europe/London.

This variable is only used if there is a item in the systemd_units list with the name systemd-timesyncd.

systemd_units

The systemd_units array is a list of systemd units to configure, for example:

systemd_units:
  - name: systemd-timesyncd
    files:
      - path: /etc/systemd/timesyncd.conf.d/timesyncd.conf
        comment: |
          Entries in this file show the compile time defaults.
          You can change settings by editing this file.
          Defaults can be restored by simply deleting this file.
          See timesyncd.conf(5) for details.
        conf:
          Time:
            NTP: 0.pool.ntp.org 1.pool.ntp.org 3.pool.ntp.org 2.pool.ntp.org
        state: present
    pkgs:
      - systemd-timesyncd
    state: enabled
    verify: systemd-timesyncd.service
  - name: systemd-networkd
    files:
      - path: /etc/systemd/network/eth0.network
        state: templated
        comment: Additional IP address added to the eth0 interface.
        conf:
          Match:
            Name: eth0
            Type: ether
          Network:
            Address:
              - 192.168.0.2/24
              - 192.168.0.3/24
            Gateway: 192.168.0.1
    verify: networking.service

The systemd_units list variables follow:

name

The name for the systemd_units list item is the name of the systemd unit to configure.

It is used as the name for the Ansible systemd module:

This parameter takes the name of exactly one unit to work with.

When no extension is given, it is implied to a .service as systemd.

When using in a chroot environment you always need to specify the name of the unit with the extension. For example, crond.service.

You can generate a YAML list of all the unit names:

systemctl list-unit-files | jc --systemctl-luf | jp [].unit_file | yq -P

See also the systemd unit configuration documentation.

files

The files variable for the systemd_units list item is an array of files to be configured for the unit, items in the files list can use the following variables:

path

The path for the item in the files list is used for the full filesystem path to the file to configure, this variables is required.

comment

The comment for the item in the files list can be used for adding commented text to the top of the file.

conf

The conf dictionary for the item in the files list defines the systemd file contents in the form of a YAML dictionary.

The depth of the dictionary defines the type of file that will be configured, fir example to enerate a systemd environment file (conf depth zero):

conf:
  Time:

The dictionary is converted into a file containing an empty section:

[Time]

To generate a systemd environment file (conf depth one):

conf:
  FOO: bar

The dictionary is converted into a environmental variables file:

FOO=bar

See the systemd environment configuration documentation.

To generate generate a systemd unit file without any duplicated entries (conf depth two):

conf:
  Unit:
    Description: Docker Compose container starter

The dictionary is converted into a file:

[Unit]
Description=Docker Compose container starter

When duplicate entries are allowed a YAML list is used (conf depth three):

conf:
  Network:
    Address:
      - 192.168.0.2/24
      - 192.168.0.3/24

The list items are are converted into duplicated keys:

[Network]
Address=192.168.0.2/24
Address=192.168.0.3/24

Note that the documentation for the general syntax of systemd configuration files includes:

Boolean arguments used in configuration files can be written in various formats. For positive settings the strings 1, yes, true and on are equivalent. For negative settings, the strings 0, no, false and off are equivalent.

If you want a value that is used as a boolean in a systemd unit file to be treated as a string you need to quote it, for example "yes", if you don't quote it then Ansible will consider numbers to be integers in the case of 1 or 0 and unquoted true and false will be booleans, the unit template, templates/unit.j2 is set to lower case booleans to avoid them becoming True and False.

Also note that duplicated sections are allowed by systemd however this role doesn't support duplicated sections in the same file.

When files are updated or deleted backups are created based on the existing file name but prefixed with a leading . and suffixed with a timestamp in ISO8601 format and the file extension .bak.

files state

The state of the item in the files list can optionally be set to one of four states when the systemd_units item is enabled or stopped, if the systemd_units item is set to absent all the items in the files list will be deleted, if the state of the item in the files list is not set then it defaults to present, the the four states are:

• absent - the file will be deleted.
• edited - if the file exists it will be edited using the Ansible ini module, as long as there are no duplicates, if there are duplicates or the file doesn't exist it cannot be edited. The edited option cannot remove variables however unlike the templated option, it preserves existing comments.
• present - if the file exists it will be edited using the Ansible ini module, as long as there are no duplicates, if there are duplicates or it doesn't exist it will be created using the templates/unit.j2 template, present is the default state.
• templated - the file will be created if it does not exist or updated if it already exists using the templates/unit.j2 template.

Don't confuse the state of the items in the files list with the state of the systemd_unit.

pkgs

The optional pkgs list of .deb packages for the systemd_units list item will be installed when the state is present and removed when absent.

systemd_units state

The systemd_units list item state can be optionally set to one of three states, if it is not set it defaults to enabled:

• absent, will result in the systemd unit being uninstalled, this means that the service will be stopped, .deb packages listed in the pkgs list will be removed and any files listed in the files array will be deleted.
• enabled, will result in the systemd unit being being installed, enabled and started. If any unit files are changed when the role is run the systemd unit will be restarted.
• stopped, will result in the systemd unit being installed, but it will be stopped and not enabled.

verify

A optional systemd service name to be passed to systemd-analyze verify, the file extension is required.

A list of services that can be verified can be generated using:

systemctl list-unit-files | jc --systemctl-luf -py

If verify is not defined and there is an existing service that has a name that matches the name, or the name with .service appended then tis service will be verified.

Usage example

This role can be included in another role along these lines (this has been based on this gist):

- name: Include systemd role
  ansible.builtin.include_role:
    name: systemd
    tasks_from: unit_present.yml
  loop: "{{ docker_systemd_units }}"
  loop_control:
    loop_var: systemd_unit
    label: "{{ systemd_unit.name }}"
  vars:
    docker_systemd_units:
      - name: docker-compose
        state: enabled
        files:
          - path: /etc/systemd/docker-compose.conf
            conf:
              DOCKER_COMPOSE_VERSION: native
          - path: /etc/systemd/service/docker-compose.service
            conf:
              Unit:
                Description: Docker Compose container starter
                After: docker.service network-online.target
                Requires: docker.service network-online.target
              Service:
                User: mailcow
                Group: mailcow
                EnvironmentFile: /etc/systemd/docker-compose.conf
                WorkingDirectory: /opt/mailcow-dockerized
                Type: oneshot
                RemainAfterExit: "yes"
                ExecStart: docker compose up -d
                ExecStop: docker compose down
              Install:
                WantedBy: multi-user.target

Notes

You can read existing systemd files as YAML on the command line using jc, for example:

cat /etc/systemd/timesyncd.conf | jc --ini -py

---
Time:
  NTP: 0.pool.ntp.org 1.pool.ntp.org 3.pool.ntp.org 2.pool.ntp.org

Note that the jc --ini parser doesn't support duplicate keys, however the --ini-dup parset that is due to be released in version 1.22.5 does, however it returms all values as a list, for example:

cat /etc/systemd/timesyncd.conf | jc --ini-dup -py

---
Time:
  NTP:
  - 0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org 3.pool.ntp.org

Dependencies

This role requires Ansible 2.13 or newer, JC and JMESPath to be installed using pip3 on the Ansible controller.

Repository

The primary URL of this repo is https://git.coop/webarch/systemd however it is also mirrored to GitHub and available via Ansible Galaxy.

If you use this role please use a tagged release, see the release notes.

Copyright

Copyright 2022-2024 Chris Croome, <chris@webarchitects.co.uk>.

This role is released under the same terms as Ansible itself, the GNU GPLv3.