GRUBCMDLINELINUX

GRUBCMDLINELINUX refers to the kernel command line options passed to the Linux kernel by the GRUB bootloader. On GRUB 2 systems, these parameters are supplied via the GRUB_CMDLINE_LINUX variable, typically defined in /etc/default/grub and used by grub-mkconfig to generate the boot menu configuration. The options control hardware behavior, security features, debugging, and performance, and are appended to the Linux boot line when the kernel is started.

Configuration is usually done by editing /etc/default/grub, for example GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" or GRUB_CMDLINE_LINUX="nomodeset pci=noacpi". After editing, the changes are applied by running update-grub (or grub2-mkconfig -o /boot/grub/grub.cfg), which rebuilds the boot menu with the new parameters.

Common options include quiet, splash, nomodeset, acpi=off, pci=noacpi, mem=, rootdelay=, mitigations=off, and others. These parameters can enable or disable features, adjust hardware initialization, or influence security and performance. Options are separated by spaces, and most are supplied as either plain flags or key=value pairs.

Caution is advised when selecting kernel parameters, as incorrect options can prevent boot or cause hardware instability. It is common to test one option at a time and consult distribution documentation for guidance. The GRUB_CMDLINE_LINUX mechanism has been a standard part of GRUB 2 configurations since its early releases, reflecting the broader shift from GRUB legacy to a more flexible, script-driven boot process.