grub2mkconfig

grub2-mkconfig is a command-line utility used to generate the GRUB 2 boot menu configuration file, typically grub.cfg. It assembles entries from installed kernels, other operating systems, and recovery options by consulting /etc/default/grub for global settings and the scripts in /etc/grub.d. The tool writes the resulting configuration to the system’s boot directory, typically /boot/grub/grub.cfg (Debian/Ubuntu) or /boot/grub2/grub.cfg (Red Hat/CentOS/Fedora).

How it works: It scans the bootable entries, optionally invoking helpers such as os-prober to detect other OSs, and expands variables defined in /etc/default/grub. The generated grub.cfg reflects the current system state and is meant to be regenerated whenever kernels or configs change. Manual edits to grub.cfg are discouraged because they can be overwritten by future runs.

Usage: The exact executable name varies by distribution. grub2-mkconfig is common on Red Hat-based systems, while grub-mkconfig or grub2-mkconfig may be used on Debian-based systems. A typical invocation requires root privileges and specifies an output file, for example: grub2-mkconfig -o /boot/grub2/grub.cfg or grub-mkconfig -o /boot/grub/grub.cfg. Running this command is a standard step after installing new kernels or changing GRUB settings.

Notes: The content of grub.cfg is dynamic and generated from templates and scripts rather than edited directly. Some distributions integrate the generation into update processes (for example, update-grub). Users should rely on /etc/default/grub and /etc/grub.d for configuration, and only run grub2-mkconfig manually when necessary.