grubupdate

Grubupdate is not a formal command in GNU GRUB; it is a colloquial term used to describe the process of regenerating the GRUB boot menu. In practice, this is accomplished by a dedicated tool that rewrites the GRUB configuration file, typically grub.cfg, after kernel updates or changes to the system.

On Debian-based systems, the standard tool is update-grub, a wrapper script provided by the grub2-common package. Running update-grub as root executes grub-mkconfig -o /boot/grub/grub.cfg, using the settings in /etc/default/grub and the scripts in /etc/grub.d. It may also invoke os-prober to detect other installed operating systems and add corresponding menu entries, unless os-prober is disabled.

On other distributions, the equivalent commands vary. Common alternatives include grub-mkconfig -o /boot/grub/grub.cfg (Arch and some others) or grub2-mkconfig -o /boot/grub2/grub.cfg (Red Hat-based setups). In EFI environments, an additional step such as grub-install may be required to ensure the bootloader is properly installed to the system’s boot medium.

Usage considerations and limitations: run grubupdate-equivalent commands as root after installing new kernels, adding or removing operating systems, or changing boot parameters. If additional OS entries are missing, verify that os-prober is installed and that GRUB_DISABLE_OS_PROBER is not set to true in /etc/default/grub. After regenerating the configuration, a reboot is typically needed to apply changes.

See also: GNU GRUB, update-grub, grub-mkconfig, grub-install, os-prober, GRUB.