Sorry but I am feeling really helpless and somehow overwhelmed by all this. I have understood, that there are two loaders and they must match in order that booting is possible.
Actually I have problems with chroot:
I am on the life-system. when I do chroot -a I will get chroot: invalid option -- 'a'.
When I type manjaro-chroot -a I get:
grub-probe: error: cannot find a GRUB drive for /dev/sdg1. Check your device.map
Of course /dev/sdg1 is the live stick and it has no boot partition.
When I type manjaro-root /dev/nvme1n1p1 which is the root partition on my btrfs system, I get:
Can't create chroot on non-directory /dev/nvme1n1p2
So I am stuck in very basic things. Then I followed the hint from @linux-aarhus and discovered:
Because - at time of writing [date=2025-03-08 timezone="Europe/Copenhagen"] - manjaro-chroot and the --automount option does not support *btrfs* .
OK, so I have to proceed with chroot.
My not booting system is located on nvme1n1.
Root is on nvme1n1p1
boot is on nvme1n1p2 and there is linux-swap.
I have found out by using gparted on the live stick. Then I saw, that the boot partition had a black i for Info on it, telling, that this partition cannot be read because of fat32.
Then I discovered by right click on this partition, that there is a “check function” in gparted. I activated it and let it perform. Then the “i” disappeared and it has the lock symbol just like it shows up on the root partition.
Then I try to follow the good advices here: https://forum.manjaro.org/t/root-tip-recovery-basic-manjaro-linux-recovery/175302#p-761121-btrfs-filesystem-19 which were new to me.
Next I wanted to mount the subvolumes of my system using:
mount -t btrfs -o subvol=@ $root /mnt but then I get:
mount: /mnt: can't find in /etc/fstab
But it seems, that I first have to mount the partitions and subvolumes of the non booting system and after that I should use chroot! – Do you see my lack of knowledge?
The help in the above mentioned source is really good, but inspite I cannot follow the instructions there. Some additional help is necessary and I have no friends who I could ask.