How to Change the Kernel Command Line Permanently (grubby and GRUB)

Updated: 28 September 2026 · Applies to: grubby 8.40 on AlmaLinux and Rocky Linux 9 and 10 and RHEL 9 and 10; GRUB on Ubuntu 24.04 and 26.04 and Debian 13

The kernel command line holds boot options such as crashkernel=, console=, transparent_hugepage= or ipv6.disable=1. This guide changes it permanently, for the current kernel and for kernels installed later. For a one-time change from the boot menu, see how to change GRUB kernel parameters before booting. On CentOS 7 and older releases the method was to edit /etc/default/grub and rebuild grub.cfg; on AlmaLinux, Rocky Linux and RHEL 9 and 10 the tool is grubby.

See the current command line

cat /proc/cmdline                  # what the running kernel was started with
grubby --info=DEFAULT              # what the default boot entry will use next time

AlmaLinux, Rocky Linux and RHEL 9 and 10

1. Add a parameter to every boot entry:

   grubby --update-kernel=ALL --args="consoleblank=0"

2. Remove one:

   grubby --update-kernel=ALL --remove-args="rhgb quiet"

3. Change only the default kernel instead of all of them: use --update-kernel=DEFAULT.
4. Check the result, then reboot:

   grubby --info=ALL | grep -E '^(title|args)'
   reboot

Kernels installed later take over the parameters of the current default kernel. If you also regenerate grub.cfg with grub2-mkconfig for other reasons, keep GRUB_CMDLINE_LINUX in /etc/default/grub in line with your changes.

Ubuntu and Debian

1. Edit /etc/default/grub. Put parameters for normal boots in GRUB_CMDLINE_LINUX_DEFAULT, and parameters for every boot, including recovery mode, in GRUB_CMDLINE_LINUX:

   GRUB_CMDLINE_LINUX_DEFAULT="quiet consoleblank=0"

2. Rebuild the boot menu and reboot:

   update-grub
   reboot

Check after the reboot

cat /proc/cmdline

Common problems

• A parameter was added twice: grubby replaces an existing name=value rather than adding a second one; check with grubby --info=ALL.
• The server does not boot with the new option: choose an older entry in the GRUB menu, or remove the option for one boot as described in the linked guide above, then undo it with --remove-args.
• Cloud or VPS images with their own settings files: some add files in /etc/default/grub.d/ that override /etc/default/grub on Ubuntu. Check that folder too.

Official documentation: Configuring kernel command-line parameters (Red Hat) and GNU GRUB manual.