Make a Permanent Change on a Persistent Live USB
Programs like Etcher, Win32DiskImager, dd, Gnome-Disks and Startup Disk Creator, create a USB with a read only operating system with a read only bootloader.
Other Programs like Rufus, Ventoy, mkusb, UNetbootin and YUMI create a USB with a Syslinux or GRUB bootloader config file that can be edited regardless if the USB is Persistent or not.
Rufus Windows:
If you are working from Windows, use Rufus to create your Live or Persistent USB.
Use the Write ISO image option
, (Default), if asked.
While still in Windows Edit /boot/grub/grub.cfg
. adding radeon.modeset=0
after quiet splash
in the first menuentry.
Then Edit /isolinux/txt.cfg
adding radeon.modeset=0
after quiet splash
in the first menu item.
Mkusb Ubuntu
If you are working from Ubuntu use mkusb to create a persistent USB with your preferred options.
Using disks, mount the USB's usbboot
partition.
Edit /boot/grub/grub.cfg
. adding radeon.modeset=0
after quiet splash
in the first menuentry.
This should set you up permanently for both BIOS and UEFI boots whether the USB is Live or Persistent.
sudo update-grub
. It returnserror: failed to get cononical path of '/cow'
.thus editing/etc/default/grub
has no effect.