Chapter 3. Setting persistent kernel tuning parameters

When you have decided on a tuning configuration that works for your system, you can make the changes persistent across reboots.

By default, edited kernel tuning parameters only remain in effect until the system reboots or the parameters are explicitly changed. This is effective for establishing the initial tuning configuration. It also provides a safety mechanism. If the edited parameters cause the machine to behave erratically, rebooting the machine returns the parameters to the previous configuration.

3.1. Making persistent kernel tuning parameter changes

You can make persistent changes to kernel tuning parameters by adding the parameter to the /etc/sysctl.conf file.

Note

This procedure does not change any of the kernel tuning parameters in the current session. The changes entered into /etc/sysctl.conf only affect future sessions.

Prerequisites

  • You have root permissions on the system.

Procedure

  1. Open /etc/sysctl.conf in a text editor.

  2. Insert the new entry into the file with the parameter’s value.

    Modify the parameter name by removing the /proc/sys/ path, changing the remaining slash (/) to a period (.), and including the parameter’s value.

    For example, to make the command echo 0 > /proc/sys/kernel/hung_task_panic persistent, enter the following into /etc/sysctl.conf: 

    # Enable gettimeofday(2)
kernel.hung_task_panic = 0
  3. Save and close the file.
  4. Reboot the system for changes to take effect.

Verification

  • To verify the configuration: 

    # cat /proc/sys/kernel/hung_task_panic
0