I have a USB disk which I use for backing up various laptops/servers at the office (bare metal backup).  The USB disk has grub 2 installed, with CentOS7.I created the USB disk with CentOS7 on a computer with no SATA hard disks - just the USB hard disk.  I can then boot that computer no problem.However, if I plug that USB disk into computers with 1,2, or 3 SATA hard disks it will not boot.  (Grub2 says BOOTMGR missing error, rescue error, or similar).  Grub2 starts (from MBR) but then has problems.Does this mean that Grub2 has hard-coded the boot partition name (/dev/sda1 or /dev/sb1 etc.) into the MBR?  So I cannot boot a system with a different number of hard disks?  (The USB disk will always be assigned a drive number higher than internal disks)Is there a way to force Grub2 to look for the boot partition regardless of drive number?
GRUB2 fails sometimes on USB bootable disk
grub2