What are kernel parameters

Kernel parameters are tunable values that you can adjust while the system is running. Note that for changes to take effect, you do not need to reboot the system or recompile the kernel.

The difference between kernel parameters and kernel command line parameters is; Kernel parameters can configure the Linux kernel with all the options, while kernel command line parameters are the specific arguments passed to the kernel during boot, allowing runtime configuration without kernel recompilation.

It is possible to address the kernel parameters through:

  • The sysctl command
  • The virtual file system mounted at the /proc/sys/ directory
  • The configuration files in the /etc/sysctl.d/ directory

Tunables are divided into classes by the kernel subsystem. Red Hat Enterprise Linux has the following tunable classes:

Table 1. Table of sysctl classes
Tunable class Subsystem

abi

Execution domains and personalities

crypto

Cryptographic interfaces

debug

Kernel debugging interfaces

dev

Device-specific information

fs

Global and specific file system tunables

kernel

Global kernel tunables

net

Network tunables

sunrpc

Sun Remote Procedure Call (NFS)

user

User Namespace limits

vm

Tuning and management of memory, buffers, and cache