grubby

command-line bootloader configuration tool for Red Hat systems

TLDR

Add kernel boot arguments to all kernel menu entries

$ sudo grubby --update-kernel=ALL --args 'quiet console=ttyS0'

Remove existing arguments from the default kernel entry

$ sudo grubby --update-kernel=DEFAULT --remove-args quiet

List all kernel menu entries

$ sudo grubby --info=ALL

grubby is a command-line tool for updating and modifying bootloader configuration on Red Hat-based systems. It works with GRUB, GRUB2, and zipl (for s390 systems), providing a unified interface for boot configuration changes.The tool modifies kernel command-line arguments, manages boot entries, and sets default kernels without directly editing configuration files. On modern Fedora/RHEL systems using GRUB2 with BLS (Boot Loader Specification), grubby modifies the individual kernel entry files in /boot/loader/entries/.

PARAMETERS

--info=KERNEL

Display boot information for specified kernel (or ALL)

--update-kernel=KERNEL

Update specified kernel (ALL, DEFAULT, or path)

--args=ARGS

Add kernel arguments

--remove-args=ARGS

Remove kernel arguments

--set-default=KERNEL

Set default boot kernel

--default-kernel

Display path of default kernel

--default-index

Display index of default kernel

--add-kernel=PATH

Add a new kernel entry (requires --title)

--remove-kernel=PATH

Remove a kernel entry

--title=TITLE

Set title for new kernel entry

--initrd=PATH

Set the initrd for a new kernel entry

--copy-default

Copy arguments and root device from the current default entry

--make-default

Make the newly added entry the default

--grub2

Use grub2-style config (default on x86_64/BLS systems)

INSTALL

sudo dnf install grubby

CAVEATS

Behavior varies between GRUB Legacy, GRUB2, and BLS configurations. Some options may not work with all bootloader configurations. Changes take effect on next boot. Always verify configuration after changes.

HISTORY

grubby was developed by Red Hat to simplify bootloader management across different configurations. It became essential for automated system management and kernel updates on Red Hat-based distributions. The original rhboot/grubby project was retired in 2022; with the adoption of BLS, its functionality now lives on as a compatible shell script maintained in Fedora's dist-git.

RESOURCES

Source code