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5.4. Collecting the boot loader configuration information by using the bootloader RHEL system role

You can use the bootloader RHEL system role to gather information about the GRUB2 boot loader entries in an automated fashion. This way you can quickly identify that your systems are set up to boot correctly, all entries point to the right kernels and initial RAM disk images.

As a result, you can for example:

  • Prevent boot failures.
  • Revert to a known good state when troubleshooting.
  • Be sure that security-related kernel command-line parameters are correctly configured.

Prerequisites

Procedure

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

    ---
- name: Configuration and management of GRUB2 boot loader
  hosts: managed-node-01.example.com
  tasks:
    - name: Gather information about the boot loader configuration
      ansible.builtin.include_role:
        name: redhat.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

Verification

  • After you run the preceding playbook on the control node, you will see a similar command-line output as in the following example: 

    ...
    "bootloader_facts": [
        {
            "args": "ro crashkernel=1G-4G:256M,4G-64G:320M,64G-:576M rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap $tuned_params quiet",
            "default": true,
            "id": "2c9ec787230141a9b087f774955795ab-6.12.el10_0.aarch64",
            "index": "1",
            "initrd": "/boot/initramfs-6.12.0.el10_0.aarch64.img $tuned_initrd",
            "kernel": "/boot/vmlinuz-6.12.0-0.el10_0.aarch64",
            "root": "/dev/mapper/rhel-root",
            "title": "Red Hat Enterprise Linux (6.12.0-0.el10_0.aarch64) 10"
        }
    ]
...

    The command-line output shows the following notable configuration information about the boot entry:

    args
    Command-line parameters passed to the kernel by the GRUB2 boot loader during the boot process. They configure various settings and behaviors of the kernel, initramfs, and other boot-time components.
    id
    Unique identifier assigned to each boot entry in a boot loader menu. It consists of machine ID and the kernel version.
    root
    The root filesystem for the kernel to mount and use as the primary filesystem during the boot.
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