>> It would help if you said which version of Debian you're using. > >And which boot parameter. Debian Bullseye. I want to add pci=nomsi to the boot parameters to troubleshoot a USB 3 issue. https://wiki.debian.org/Grub#Configuring_GRUB_v2 says that /etc/default/grub ought to exist, if it doesn't should the wiki be updated?