Linux – Unable to create bootable USB to mount kali linux iso image

You could solve your problem by following these steps :

Find out which devices are available by typing ls

Set to the correct value :

set prefix=(hd0,1)/grub
set root=(hd0,1)
insmod normal
normal

The above commands will get you out of the rescue mode to the normal terminal mode. After the above commands you can go ahead and start the rest of the settings.

insmod linux 
linux /vmlinuz root=/dev/sdXY ro 

If the above command doesnt work try this :

linux /boot/vmlinuz-3.2.0-14-generic root=/dev/sda1 ro
boot

Additionally dont forget to update your grub

Update the GRUB config file.:

sudo update-grub

Reinstallation of Grub on the device:

sudo grub-install /dev/sdX

hope it helps

Around the time when Windows 98 was mainstream, bootable MS-DOS CDs and USB drives used a 1.44MB floppy disk image as the actual boot target. The CD/USB drive stores the floppy image either visibly on the file system or invisibly outside of a partition, and the computer would boot to a virtual A:\ drive. If access to the CD/USB drive is desired after boot, the appropriate driver must be present on the floppy image and loaded.

At least in some cases, booting from the floppy image requires features implemented in BIOS. (I remember trying to make a rescue disk on a state-of-the-art 32MB USB drive, and there being different instructions for BIOS that support USB-FDD, USB-ZIP, USB-HDD, etc.)

If you don't feel like hunting down period-appropriate documentation and tools, your best bet is probably a MS-DOS floppy image paired with a modern bootloader that supports memdisk features. syslinux/isolinux and GRUB4DOS comes to mind.