Boot Process

There are no specific modules for managing a linux system’s boot process with Ansible. However, you can use your pre-existing knowledge of the boot process to manage related files. You can use the file module to manage systemd boot targets. Or lineinfile to manage the GRUB configuration.

The reboot module does let you to reboot a host though. And it will pick up after the reboot at the exact same location in a playbook.

Managing Systemd Targets (symlink method)

To manage the default systemd target, the /etc/systemd/system/default.target file must exist as a symbolic link to the desired default target:

ls -l /etc/systemd/system/default.target
    lrwxrwxrwx. 1 root root 37 Mar 23 05:33 /etc/systemd/system/default.target -> /lib/systemd/system/multi-user.target

Let’s use the file module to change the symlink, targeting graphical mode instead:

---
- name: set default boot target
    hosts: ansible2
    tasks:
    - name: set boot target to graphical
      file:            
        src: /usr/lib/systemd/system/graphical.target
        dest: /etc/systemd/system/default.target
        state: link

Managing Systemd Targets (systemctl method)

This method isn’t great because you have to run around with your head cut off trying to figure out a way to make it indempotent.

- block:
  - name: Install GUI package group
    ansible.builtin.dnf:
      name: "@Server with GUI"
      state: present

  - name: get current target
    ansible.builtin.command: "systemctl get-default"
    changed_when: false
    register: systemdefault

  - name: Set default to graphical target
    ansible.builtin.command: "systemctl set-default graphical.target"
    when: "'graphical' not in systemdefault.stdout"
    changed_when: true

  when: gui_enabled | bool

Rebooting Managed Hosts

As mentioned, the reboot module is used to restart managed nodes. And the test_command argument verifies that the host is available after the reboot. test_command specifies a command that Ansible should run on the managed hosts after the reboot. If the command is successful, then Ansible knows to continue.

There are also arguments related to timeouts:

Argument	Purpose
connect_timeout	Maximum seconds to wait for a successful connection before trying again.
post_reboot_delay	Seconds to wait after the reboot command before trying to check if a host is available.
pre_reboot_delay	Seconds to wait before issuing the reboot.
reboot_timeout	Maximum seconds to wait for the rebooted machine to respond to the test command.

Let’s change default target and reboot the system:

---
- name: Set default target to graphical
  hosts: practice
  become: yes
  tasks:
  - name: Link graphical.target to default.target
    file:
      src: /usr/lib/systemd/system/graphical.target
      dest: /etc/systemd/system/default.target
      state: link

  - name: reboot
    reboot:
      test_command: whoami
      msg: rebooting...

  - name: print success message
    debug:
      msg: Reboot successful

You can test that the reboot was issued successfully by using:

ansible some-host -a "systemctl get-default"

Finding help

You may need to search man pages to find more info:

$ man -k systemd

The relevant man pages here may be:

systemd.target (5)   - Target unit configuration
systemd.unit (5)     - Unit configuration

I didn’t find exact instructions on how to change the default target. But there is information on symlinking in the systemd.unit. And also mentions using the systemctl command to make the symlink:

 As another example, default.target —
       the default system target started at boot — is commonly aliased
       to either multi-user.target or graphical.target to select what
       is started by default.

If you can’t remember the search path, the paths are listed at the top of the systemd-unit man page:

$ man systemd.unit

  System Unit Search Path
       /etc/systemd/system.control/*
       /run/systemd/system.control/*
       /run/systemd/transient/*
       /run/systemd/generator.early/*
       /etc/systemd/system/*
       /etc/systemd/system.attached/*
       /run/systemd/system/*
       /run/systemd/system.attached/*
       /run/systemd/generator/*
       ...
       /usr/lib/systemd/system/*
       /run/systemd/generator.late/*

If you can remember that you need to symlink a unit to /etc/systemd/system/default.target then I think you’ll be good here.

You can also check options for the systemctl command:

$ systemctl --help | grep default
  get-default                         Get the name of the default target
  set-default TARGET                  Set the default target

You’ll also want to remember where systemd keeps all of the default unit files. List is listed at the top of the systemd man page:

$ man systemd | head
SYSTEMD(1)                      systemd                     SYSTEMD(1)

NAME
       systemd, init - systemd system and service manager

SYNOPSIS

       /usr/lib/systemd/systemd [OPTIONS...]

       init [OPTIONS...] {COMMAND}

The file module documentation has a symlink example at the bottom:

ansible-doc file

- name: Create a symbolic link
  ansible.builtin.file:
    src: /file/to/link/to
    dest: /path/to/symlink
    owner: foo
    group: foo
    state: link

Just use similar methods (managing settings file) to change GRUB settings and other boot options. Feel free to reach out for any clarifications needed. :)