Chapter 30. Configuring kernel parameters permanently by using the RHEL system role

Procedure

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

   ---
   - name: Configure kernel settings
     hosts: managed-node-01.example.com
     roles:
       - 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

   • name: optional key which associates an arbitrary string with the play as a label and identifies what the play is for.
   • hosts: key in the play which specifies the hosts against which the play is run. The value or values for this key can be provided as individual names of managed hosts or as groups of hosts as defined in the inventory file.
   • vars: section of the playbook which represents a list of variables containing selected kernel parameter names and values to which they have to be set.

   • role: key which specifies what RHEL system role is going to configure the parameters and values mentioned in the vars section.

     Note

     You can modify the kernel parameters and their values in the playbook to fit your needs.

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

4. Restart your managed hosts and check the affected kernel parameters to verify that the changes have been applied and persist across reboots.