Skip to main content

sysctl

Introduction​

This cheat sheet provides a quick reference for common concepts and commands related to sysctl in Linux. sysctl is a command-line utility that allows you to view and modify kernel parameters at runtime.

sysctl Concepts​

Kernel Parameters​

Kernel parameters, also known as sysctl variables, control various aspects of the Linux kernel's behavior.

Viewing Kernel Parameters​

Use sysctl to view the current values of kernel parameters.

  • Display the value of a specific kernel parameter:

    sysctl kernel.parameter_name

  • List all kernel parameters and their values:

    sysctl -a

  • Show only parameters in a specific namespace (e.g., net):

    sysctl -a --pattern ^net\.

Modifying Kernel Parameters​

You can modify kernel parameters using sysctl, but be cautious as incorrect changes can affect system stability.

  • Set a kernel parameter to a specific value (temporary):

    sysctl -w kernel.parameter_name=new_value

  • To make a change permanent, edit the /etc/sysctl.conf file and add or update parameter values.

Reload Configuration​

After editing /etc/sysctl.conf, you can apply the changes without rebooting.

  • Reload the sysctl settings from /etc/sysctl.conf:
    sysctl -p

Security Considerations​

Be cautious when modifying kernel parameters, as incorrect changes can impact system stability and security.

  • Avoid setting kernel parameters without understanding their implications.

sysctl Command-Line​

  • Display the value of a specific kernel parameter:

    sysctl kernel.parameter_name

  • List all kernel parameters and their values:

    sysctl -a

  • Show only parameters in a specific namespace (e.g., net):

    sysctl -a --pattern ^net\.

  • Set a kernel parameter to a specific value (temporary):

    sysctl -w kernel.parameter_name=new_value

  • Reload the sysctl settings from /etc/sysctl.conf:

    sysctl -p

Conclusion​

This cheat sheet covers common concepts and commands for working with sysctl in Linux. sysctl is a powerful tool for configuring kernel parameters at runtime, but it should be used with caution to avoid unintended consequences; refer to the sysctl manual for more in-depth information and advanced usage.