Chapter 31. Configuring the GRUB boot loader by using RHEL system roles

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Configuration and management of GRUB boot loader
     hosts: managed-node-01.example.com
     tasks:
       - name: Update existing boot loader entries
         ansible.builtin.include_role:
           name: rhel-system-roles.bootloader
         vars:
           bootloader_settings:
             - kernel:
                 path: /boot/vmlinuz-5.14.0-362.24.1.el9_3.aarch64
               options:
                 - name: quiet
                   state: present
           bootloader_reboot_ok: true

   The settings specified in the example playbook include the following:

   kernel

   Specifies the kernel connected with the boot loader entry that you want to update.

   options

   Specifies the kernel command-line parameters to update for your chosen boot loader entry (kernel).

   bootloader_reboot_ok: true

   The role detects that a reboot is required for the changes to take effect and performs a restart of the managed node.

   For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.bootloader/README.md file on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml

Procedure

1. Store your sensitive variables in an encrypted file:

   1. Create the vault:

      $ ansible-vault create vault.yml
      New Vault password: <vault_password>
      Confirm New Vault password: <vault_password>

   2. After the ansible-vault create command opens an editor, enter the sensitive data in the <key>: <value> format:

      pwd: <password>

   3. Save the changes, and close the editor. Ansible encrypts the data in the vault.

2. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Configuration and management of GRUB boot loader
     hosts: managed-node-01.example.com
     vars_files:
       - vault.yml
     tasks:
       - name: Set the bootloader password
         ansible.builtin.include_role:
           name: rhel-system-roles.bootloader
         vars:
           bootloader_password: "{{ pwd }}"
           bootloader_reboot_ok: true

   The settings specified in the example playbook include the following:

   bootloader_password: "{{ pwd }}"

   The variable ensures protection of boot parameters with a password.

   bootloader_reboot_ok: true

   The role detects that a reboot is required for the changes to take effect and performs a restart of the managed node.

   Important

   Changing the boot loader password is not an idempotent transaction. This means that if you apply the same Ansible playbook again, the result will not be the same, and the state of the managed node will change.

   For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.bootloader/README.md file on the control node.

3. Validate the playbook syntax:

   $ ansible-playbook --syntax-check --ask-vault-pass ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

4. Run the playbook:

   $ ansible-playbook --ask-vault-pass ~/playbook.yml

Verification

1. On your managed node during the GRUB boot menu screen, press the e key for edit.

   

2. You are prompted for a username and a password:

   

   Enter username: root

   The boot loader username is always root and you do not need to specify it in your Ansible playbook.

   Enter password: <password>

   The boot loader password corresponds to the pwd variable that you defined in the vault.yml file.

3. You can view or edit configuration of the particular boot loader entry:

   

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Configuration and management of the GRUB boot loader
     hosts: managed-node-01.example.com
     tasks:
       - name: Update the boot loader timeout
         ansible.builtin.include_role:
           name: rhel-system-roles.bootloader
         vars:
           bootloader_timeout: 10

   The settings specified in the example playbook include the following:

   bootloader_timeout: 10

   Input an integer to control for how long the GRUB boot loader menu is displayed before booting the default entry.

   For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.bootloader/README.md file on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml

Verification

1. Remotely restart your managed node:

   # ansible managed-node-01.example.com -m ansible.builtin.reboot
   managed-node-01.example.com | CHANGED => {
       "changed": true,
       "elapsed": 21,
       "rebooted": true
   }

2. On the managed node, observe the GRUB boot menu screen.

   

   The highlighted entry will be executed automatically in 10s

   For how long this boot menu is displayed before GRUB automatically uses the default entry.

   • Alternative: you can remotely query for the "timeout" settings in the /boot/grub2/grub.cfg file of your managed node:

     # ansible managed-node-01.example.com -m ansible.builtin.command -a "grep 'timeout' /boot/grub2/grub.cfg"
     managed-node-01.example.com | CHANGED | rc=0 >>
     if [ x$feature_timeout_style = xy ] ; then
       set timeout_style=menu
       set timeout=10
     # Fallback normal timeout code in case the timeout_style feature is
       set timeout=10
     if [ x$feature_timeout_style = xy ] ; then
         set timeout_style=menu
         set timeout=10
         set orig_timeout_style=${timeout_style}
         set orig_timeout=${timeout}
           # timeout_style=menu + timeout=0 avoids the countdown code keypress check
           set timeout_style=menu
           set timeout=10
           set timeout_style=hidden
           set timeout=10
     if [ x$feature_timeout_style = xy ]; then
       if [ "${menu_show_once_timeout}" ]; then
         set timeout_style=menu
         set timeout=10
         unset menu_show_once_timeout
         save_env menu_show_once_timeout

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Configuration and management of GRUB boot loader
     hosts: managed-node-01.example.com
     tasks:
       - name: Gather information about the boot loader configuration
         ansible.builtin.include_role:
           name: rhel-system-roles.bootloader
         vars:
           bootloader_gather_facts: true
   
       - name: Display the collected boot loader configuration information
         debug:
           var: bootloader_facts

   For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.bootloader/README.md file on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml