Which file would you edit to change GRUB boot parameters?

The configuration file that you would edit to change GRUB boot parameters is located at /etc/default/grub. This file contains default settings that are used by the GRUB (Grand Unified Bootloader) at boot time. By modifying this file, you can easily adjust options such as the default kernel to boot, timeout settings, and additional kernel parameters.

After making changes to /etc/default/grub, it is essential to run the command update-grub or grub2-mkconfig -o /boot/grub/grub.cfg (depending on the distribution) to apply those changes to the GRUB configuration file used during the boot process. This process regenerates the grub.cfg file, which is the one utilized at boot time and contains all the actual boot menu entries and configurations for GRUB.

The other file options are not relevant for changing GRUB parameters. For instance, /etc/fstab is related to file system mounting information, /boot/grub/grub.cfg is auto-generated from /etc/default/grub and should not be edited directly, and /etc/passwd is used for user account information.