I believe, you should simply remove or comment out the entries in /etc/default/grub, and then just do an
upgrade-initramfs -u as root to make it permanent. Before you do this, you can check your setings. In the boot menu of grub, type "e", then you can edit the boot commands for this special boot. Just remove it or edit the parms to your need, then go on booting pressing "F10"- key. Next reboot will be as before. Doing so, you can set all settings, before changing anything in /etc/default/grub Hope this helps. Best Hans
