Kernparameters

Kernparameters are settings that control the behavior of a computer's kernel. They influence hardware detection, resource management, scheduling, networking, security features, and debugging options. Kernparameter settings can be supplied to the kernel at boot time or adjusted at runtime. In Linux, boot-time kernel parameters are passed to the kernel via the bootloader, typically by appending options to the Linux command line in GRUB or another boot manager. These parameters affect early initialization, device drivers, and subsystem behavior. Kernel parameters that can be changed after boot are exposed through interfaces such as /proc/sys and /sys, and they can be inspected with commands like cat /proc/cmdline and sysctl -a. Changes may be applied temporarily or made persistent through configuration files.

Boot-time examples include quiet to reduce boot messages, nomodeset to disable kernel mode setting for graphics, mem= to limit memory, maxcpus= to limit CPUs, and root= to specify the root filesystem. Runtime examples include net.ipv4.ip_forward to enable forwarding of packets, vm.swappiness to influence swap behavior, kernel.core_pattern to control core dumps, and fs.file-max to adjust the maximum number of open files. These values are often managed with the sysctl utility, which reads and writes values under /proc/sys; persistent changes can be placed in /etc/sysctl.conf or files under /etc/sysctl.d.

Notes: Documentation varies by kernel version and architecture; altering kernparameter values can affect stability and security, so changes should be tested and backed up.