GRUB installation via copy&paste?

[Roland Hummel]

Hello,

my university allowed me to set up a multiboot environment in a computer 
pool equipped with iMacs (running MacOS 10.11.6 El Capitan) to give the 
students the possibility to work under GNU/Linuxas well. I have problems 
with the GRUB configuration and kindly want to ask for help:

I've set up a test environment with a parallel installation of MacOS and 
a GNU/Linux (currently elementaryOS), OS selection via rEFInd boot 
manager [1]. Then I've cloned the GNU/Linux with Clonezilla [2] to a 
test the prepared GNU/Linux on a target system. I've copied the grub 
configuration from the source system to the target system and replaced 
the UUID of the source system partition with the one of the system 
partition of the target system. Unfortunately the target system just 
boots into GRUB.

I know there are dozens of tutorials out there "how to fix GRUB" but the 
challenge in my case is that I need a "deployment setup" in the end that 
works with commands available from the MacOS command line, because there 
is no deployment environment for the final "rollout", just NFS storage 
where I can save the "deployment files" like the image prepared with 
Clonezilla, the rEFInd and GRUB configuration. Obviously I don't want to 
set up the multiboot environment on every Mac manually but with a script 
executed under MacOS which is the preinstalled OS on all systems here.

I think that there is something wrong with the UUID in the grub.cfg of 
the target system. According to

TargetMac:~ root# diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       
IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     
disk0
   1:                        EFI EFI                     209.7 MB   
disk0s1
   2:                  Apple_HFS Apple OS X              871.0 GB   
disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   
disk0s3
   4:           Linux Filesystem                         111.2 GB   
disk0s4
   5:                 Linux Swap                         17.2 GB    
disk0s5
TargetMac:~ root# diskutil info /dev/disk0s4
   Device Identifier:        disk0s4
   Device Node:              /dev/disk0s4
   Whole:                    No
   Part of Whole:            disk0
   Device / Media Name:      Linux filesystem

   Volume Name:              Not applicable (no file system)

   Mounted:                  Not applicable (no file system)

   File System:              None

   Partition Type:           Linux Filesystem
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 SATA
   SMART Status:             Verified
   Disk / Partition UUID:    ABC0EEAF-A36A-4004-98E4-5C4E8C423BD8

   Total Size:               111.2 GB (111159225856 Bytes) (exactly 
217107863 512-Byte-Units)
   Volume Free Space:        Not applicable (no file system)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (no file system)

   Device Location:          Internal
   Removable Media:          No

   Solid State:              No

TargetMac:~ root#

I should use the following GRUB configuration:

search.fs_uuid abc0eeaf-a36a-4004-98e4-5c4e8c423bd8 root hd0,gpt4
set prefix=($root)'/boot/grub'
configfile $prefix/grub.cfg

(which I added under MacOS via "mkdir /Volumes/ESP && mount -t msdos 
/dev/disk0s1 /Volumes/ESP" in "/Volumes/ESP/EFI/ubuntu/grub.cfg").

A reboot into the GNU/Linux system ends up in GRUB. Any idea how what I 
have to fix to boot the GNU/Linux system or is this the wrong way to 
configure GRUB, even in my special case?

Bets regards and thank you for any help
Roland

[1] https://www.rodsbooks.com/refind/
[2] https://clonezilla.org/