Boot problem after cloning

Guess this is the first time I post a question here. Have been playing with Linux and VMware servers for more than 10 years now. Lately I decided to move my focus on Debian desktops and ProxMox (again). Reasons being more privacy friendly, broader hardware support and lower resource reqs. So bye bye Windows (for now) and Intel/AMD (later on). Have been working hard to compose my own Debian desktop from scratch, picking XFCe for GUI. Works quite nice now (not as slick as Windows, but smarter, faster), but with a lot of loose ends to tie up. One of em being the lack of genuine Microsoft fonts (working on that), another being Samba on my (home brew) NASses: gives a number of issues with Linux applications (locking problems, not able to create shortcuts on the NAS, etc). Will try and see how NFS goes later. My problem, however: Having converted my 1st Windows desktop to a Debian/XFCe desktop I am about to convert my 2nd Windows desktop. I've used Clonezilla v2.2.3 for years and it served me well. When trying to backup Debian v11 (Bullseye) though, it didn't work so well. Had to upgrade to Clonezilla v3.0.1. Now for the cloning part: my three Windows desktops have identical hardware, and cloning Windows (with Clz v2.2.3) always went well (of course changing licence keys, IPs and hostnames). But when I clone my Debian desktop (with disk-to-image backup and image-to-disk restore), I can't make the clone to boot. BIOS/UEFI says 'Reboot and select proper boot device'. Tried to fix it myself. Read a number of posts (many ArchLinux and Ubuntu by the way) and finally tried this: www.debian.org/releases/stable/amd64/ch08s06.en.html Using my Debian installation USB stick I was able to get into Rescue Mode and have the installer reinstall GRUB on my boot disk: it ended with: "Execution of 'grub-install /dev/sda' failed". Most of the other articles I read point in the same direction, so I'm kinda stuck. My questions: Does anybody have good experiences with cloning Linux systems with Clonezilla? Any idea how I could go on from here? Additional info: My partiton layout is: # Size In use Free iSize Type/description 1 499 MB 4 MB 495 MB 476 MiB EFI/boot partition (/boot/efi) 2 40,0 GB 11,8 GB 28,2 GB 37,3 GiB Linux root (/) 3 16,1 GB 10,0 GB PM 9,3 GiB Linux swap 4 70,0 GB 12,3 GB 57,7 GB 65,2 GiB Linux home (/home) - 120 GB PM 120 GB 111,3 GiB Free space 1st partition starts at sector 2048 (partition alignment is at 1 MB intervals). Sector 0 = boot sector, sector 2-33 is (primary?) GPT partition table. Don't know what sector 1 is used for. Wikipedia says GPT is GUID (UUID) based. I'm aware that with GPT every disk (and partition on it) has a UUID. Can't remember if I had to fix that when cloning Windows in the past. On the other hand: overriding a UUID during cloning to me seems only a possible problem if the old UUID is actually stored in NVRAM in the BIOS/UEFI. I've not seen an indication for this in my (AMI) BIOS boot menu. On my live desktop I see a directory called 'EFI' under '/boot/efi'. The latter directory was empty when I looked at it on my clone system under Rescue Mode. But I guess that's OK since I learned that my 1st partition is mounted under /boot/efi during normal bootup. Final remarks: I've searched through this forum and found slightly related posts, but not close enough. And I hope my personal introduction is not considered too long or off topic. Awaiting your reactions, With kind regards, Steijn van Essen *From i8088 to i7-980X in 25 years and still waiting … But not for much longer: when Windows is gone, Intel will be next (in favor of ARM on Raspberry Pi)*