Mdthbs

Can I move working boot partition / root filesystem to another drive/partition and just boot from there?

Or device names will be changed and prevent from working?

If you use UUIDs in /etc/fstab (and other related files that may be relevant in your distro), like /dev/disk/by-uuid/57c59366-9196-4613-ba53-5ad24dcecfb9, and adjust your boot loader configuration if you move your kernel boot partition, then it should work.

Yes it is possible. Also its not easy. If you intent to move separated /boot partition and or / partition you should consider first of all changing the fstab entries.

If you are moving the files to new partition then don't forget to use cp -p while copying to preserve permissions. adjust then your /etc/fstab to the new UUID's of partitions that you will use. YOu can get the partition uuid by running blkid /dev/sdXn where X is name of the drive and n number of partition.

You can also use blkid to attach labels to your partitions and then mount via labels which is much easier read man blkid to learn more.

After you change the partitions and adjust /etc/fstab you should run the update-grub - available on Debian/Ubuntu script or grub-mkconfig -o /boot/grub/grub.cfg to generate a new config file and then reinstall grub into the first hdd that you bot from. grub-install --recheck /dev/sda

Of course do not forget that when copiying mount a new / or /boot partition on /mnt and after copying all of the files mount them as / and /boot chroot and only then run update of the grub if you want things to be done correctly.

I just like to mention what I did to move Debian Stretch installed in old MBR style disk which is near to dying and moved the OS to new disk with GPT, in my case ESP(EFI system partition) is present in old disk, so I was already booting using UEFI. I followed answer already given above by user in1t3r .

1. Get gparted live in usb


2. Boot with gparted live, select old drive select partition, copy partition
   
   Select new drive paste partition, save changes.
   Do this for root(& boot) and ESP(EFI system partition)


3. Boot to OS in old drive as normal.


4. Run sudo gdisk, go to new /dev/sdX check ESP partition, if incorrect set to type ef00. (use ? or 'help' command)


5. Check the UUID of partiotions copied n new drive, use command sudo blkid, (blkid is part of the e2fsprogs package)


6. If UUID is not different than OLD partition change UUID of new partition copied in new drive,
   
   Use command, tune2fs -U random /dev/sdXy
   
   if it ask to run, e2fsck -f /dev/sdbXy , run it then run tune2fs.


7. Create mount point directory '/newpart' to mount new drive partition.


8. Mount new drive OS root(and boot) partitions,
   
   a) root drv; sudo mount /dev/sdbXx /newpart
   
   b) ESP drv; sudo mount /dev/sdbXy /newpart/boot/efi


9. We need to update and generate new grub, but for that we need to chroot to new partition as root
   
   mount dev,proc,sys on '/newpart' dev,proc,sys
   
   sudo mount --rbind /dev /newpart/dev
   
   sudo mount --rbind /proc /newpart/proc
   
   sudo mount --rbind /sys /newpart/sys


10. Change /etc/fstab on both new OS part (/newpart/etc/fstab) and old to point root(/) and boot if exists to new UUID,
    
    UUID=[new-part-UUID] , comment the old one


11. chroot to '/newpart', sudo chroot /newpart


12. Run
    
    a) grub-install --recheck
    
    c) update-grub
    
    b) grub-install --recheck
    
    d) exit (to exit from chroot)


13. Unmount dev,proc,sys (mount --make-rslave needed 1st for recursive umount)
    
    sudo mount --make-rslave /newpart/sys
    
    sudo mount --make-rslave /newpart/proc
    
    sudo mount --make-rslave /newpart/dev
    
    sudo umount -R /newpart/sys
    
    sudo umount -R /newpart/proc
    
    sudo umount -R /newpart/dev
    
    sudo umount /newpart


14. Correct the old OS /etc/fstab to point root(/) and boot id exists as before, (NOTE don't change in new disk)


15. Reboot,


16. GO to UEFI-BIOS, chose new disk as boot priority


17. ON rebooting with new drive ESP, Grub menu will appear, go to 1st menu wiz. OS on new drive .
    
    (Second menu is for OS in old drive)