Chapter 14. Configuring kernel parameters permanently by using RHEL system roles

Procedure

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

   ---
   - name: Configuring kernel settings
     hosts: managed-node-01.example.com
     tasks:
       - name: Configure hugepages, packet size for loopback device, and limits on simultaneously open files.
         ansible.builtin.include_role:
           name: redhat.rhel_system_roles.kernel_settings
         vars:
           kernel_settings_sysctl:
             - name: fs.file-max
               value: 400000
             - name: kernel.threads-max
               value: 65536
           kernel_settings_sysfs:
             - name: /sys/class/net/lo/mtu
               value: 65000
           kernel_settings_transparent_hugepages: madvise
           kernel_settings_reboot_ok: true

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   The settings specified in the example playbook include the following:

   kernel_settings_sysfs: <list_of_sysctl_settings>

   A YAML list of sysctl settings and the values you want to assign to these settings.

   kernel_settings_transparent_hugepages: <value>

   Controls the memory subsystem Transparent Huge Pages (THP) setting. You can disable THP support (never), enable it system wide (always) or inside MAD_HUGEPAGE regions (madvise).

   kernel_settings_reboot_ok: <true|false>

   The default is false. If set to true, the system role will determine if a reboot of the managed host is necessary for the requested changes to take effect and reboot it. If set to false, the role will return the variable kernel_settings_reboot_required with a value of true, indicating that a reboot is required. In this case, a user must reboot the managed node manually.

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

2. Validate the playbook syntax:

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

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   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

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