Updated: 30 September 2026 · Applies to: grubby with GRUB 2 and Boot Loader Specification entries on AlmaLinux and Rocky Linux 9 and 10 and RHEL 9 and 10
Kernel arguments (also called kernel command-line parameters) control things such as the console, crash dumps, or hardware quirks. On AlmaLinux, Rocky Linux and RHEL, the boot entries are small files in /boot/loader/entries/, and grubby is the tool to change their arguments. Editing /etc/default/grub alone, as on older CentOS releases, is not enough: without --update-bls-cmdline, the existing entries keep their old arguments. We tested the commands below on AlmaLinux 10.
1. See the current arguments
cat /proc/cmdline # arguments of the running kernel grubby --info=DEFAULT # the default boot entry grubby --info=ALL | grep -E '^(kernel|args)'
2. Add or remove arguments for all kernels
grubby --update-kernel=ALL --args="console=ttyS0,115200" grubby --update-kernel=ALL --remove-args="rhgb quiet"
Arguments are matched by name when you remove them: --remove-args="resume" removes resume=... whatever its value. New kernels installed later inherit the arguments of the default entry.
3. Change only one kernel
grubby --update-kernel=/boot/vmlinuz-$(uname -r) --args="loglevel=7"
This is useful to test an argument on one kernel before applying it to all.
4. Reboot and check
reboot cat /proc/cmdline
Other useful grubby commands
grubby --default-kernel # which kernel boots by default grubby --set-default=/boot/vmlinuz-VERSION # choose another default kernel
If you use /etc/default/grub
You can also add arguments to GRUB_CMDLINE_LINUX in /etc/default/grub. Then regenerate the configuration and update the existing entries in one step:
grub2-mkconfig -o /boot/grub2/grub.cfg --update-bls-cmdline
--update-bls-cmdline replaces the arguments of every boot entry with those from /etc/default/grub, so an argument you added only with grubby is removed. Use one method consistently.
On UEFI systems the path is the same on current releases: /boot/grub2/grub.cfg, which the file in the EFI partition loads.
For examples, see how to remove the rescue kernel and boot entry with grubby.
Official documentation: RHEL 9: configuring kernel command-line parameters.
