Knowledge Base:Adjusting GRUB settings for a single boot session

Synopsis

When troubleshooting boot failures or trying to make changes for kernel settings, users might want to boot their system with a particular change in the GRUB bootloader configuration for a single boot session (i.e. not persistent).

Environment

Gentoo Linux systems using GRUB as the bootloader.

Analysis

With GRUB, it is possible to boot with different settings for just a single boot session. Changes made herein are not persisted, so rebooting afterwards will boot back using the "old" configuration settings.

Resolution

1. During bootup, wait until the GRUB boot menu is displayed. The default timeout for GRUB is 30 seconds (if necessary press any key other than Enter or → to halt the timeout);
2. Navigate to the entry desired boot from, but do not press the Enter key. Instead, press the E key (which stands for edit);
3. Navigate to the line needed to be modified (which is most likely the one starting with kernel, but can also be the root or initrd line) and press E again to edit this specific line. When finished changing the line, press the Enter key;
4. When all required changes have been made to the line(s), press the B key to boot the entry.

If happy with the result, do not forget to update /boot/grub/grub.conf with changes made in the steps above for persistent result.