Ansible Systemd Service Role

This Ansible role sets up and configures systemd service unit files. It helps you run services automatically in the background, manage when they're enabled or disabled, handle groups of processes, and set up dependencies on other services.

Key Tasks

1. Creates a systemd service file in /etc/systemd/system/ named service_name.service for each item in systemd_service.
2. Configures important options in the Unit, Service, and Install sections.
3. Informs systemd about new service files and restarts the service.
4. Enables the service to start automatically on boot if needed.

This role works with all versions of Ubuntu.

Requirements

To run this role, you need root access. You can either run it in a playbook with a global become: yes option, or include it in your playbook like this:

- hosts: apps
  roles:
    - role: systemd-service
      become: yes

Role Variables

You can define services using the systemd_service dictionary variable (see defaults/main.yml):

systemd_service: {}

For each service, you need to specify service_name and other necessary values. For example, to set the service to start on boot, use the enabled parameter:

systemd_service:
  service_name:
    enabled:

Unit Section Options

This group includes general information about the unit.

description:   # A description of the unit

The following parameters specify dependencies on other units. If the service starts, the listed units will start too. If a unit from requires fails, the service will also stop. If a unit from wants fails, the service will continue running. Use space-separated unit names for these parameters:

requires:   # Units that must start with the service
wants:      # Units that should start with the service

To set the order for starting or stopping services, use these parameters:

after:   # Units to start after this service
before:  # Units to start before this service

Service Section Options

This section includes details about the service and process it supervises. The type parameter specifies how the process starts.

type:

Possible values:

• simple - service starts immediately and doesn't create child processes.
• forking - service starts once, then forks a new process. This requires a pid_file parameter to identify the main process.

Other values include:

• oneshot, dbus, notify, and idle, each with specific behaviors.

Set a path for the PID file if using the forking type:

pid_file:    # Path to the service's PID file

You can specify the user and group under which the service runs:

user:
group:

Set a scheduling priority:

nice:    # The service's priority level

The oom_score_adjust parameter adjusts memory killer behavior:

oom_score_adjust:

You can define commands to execute based on the service's state, using parameters for start, stop, and reload actions:

exec_start:
exec_start_pre:
exec_start_post:
exec_stop:
exec_stop_post:
exec_reload:

Control whether the service restarts based on specific conditions with the restart parameter:

restart:

Set delays for restart and timeout with parameters:

restart_sec:
timeout_sec:

Use the environment parameter for environment variables:

environment:       # List of environment variables
environment_file:  # Path to a file with environment variables

Specify the working directory:

working_directory:

Control where standard input and output connect:

standard_input:
standard_output:
standard_error:

Install Section Options

This section carries installation information for the unit. These parameters can be used to define which units refer to this service.

wanted_by:
required_by:

Dependencies

None.

Example Playbook

- hosts: app
  roles:
    - role: systemd-service
      systemd_service:
        # Service name
        railsapp:
          # Start the service on boot
          enabled: Yes
          # Command to run when starting the service
          exec_start: "/bin/bash -lc 'puma -C config/puma.rb'"
          # Current working directory
          working_directory: "/var/www/myapp"
          # User and group to run the service
          user: "deploy"
          group: "deploy"
          # Restart settings for the service
          restart: "on-failure"
          # Activate 'redis' if possible
          wants: "redis.service"
          # Activate 'postgresql' or stop if failed
          requires: "postgresql.service"
          # Specify preferred unit to run the service
          wanted_by: "multi-user.target"

License

Licensed under the MIT License.