Tue 23 Dec 2014 12:23:57 PM UTC, original submission:
SETUP:
=====
- OS-partition is BTRFS on /dev/sda OR (hd0,msdos1)
(only subvolumes in the root of this partition!)
- I have a fresh install of Debian8 on the subvolume /root.
(GRUB's config is in /root/boot/grub)
- I put an old ubuntu installation on the subvolume /ubuntu_root.
subvolume /root was default, but reverted to ` btrfs su set 0 /`
(as well as subvolid=5 respectively; does not change anything)
OBSERVED BEHAVIOR:
=================
I cannot configure grub to boot from another subvolume, where the config is located.
in the grub> console:
#1: check root-var
grub> echo $root
hd0,msdos1
#2: showing my subvoumes:
grub> ls (hd0,msdos1)
btrfs volume; UUID=...
grub> ls (hd0,msdos1)/
/root /ubuntu_root
#3: houston, we've got a problem
# '(hd0,msdos1)/root/' is listed here!
ls root
/bin /boot ... /vmlinuz
SUMMARY: I can correctly list my subvolumes, as in 2). When setting the (necessray) root-var, some magic seems to happen, as in 3). I cannot specify the subvolume (hence the correct path) to root, kernel or initrd.
#4: When entering commands manually
# I can at least boot into initramfs...
grub> linux (hd0,msdos1)/ubuntu_root/vmlinuz root=UUID... rootflags=subvol=/ubuntu_root
grub> initrd (hd0,msdos1)/ubuntu_root/initrd.img
!!! sidenote only !!!
Idk why, but 3 days (and some updates) ago, `update-grub` was able to find the ubuntu-installation.
!!! the config was not bootable though !!!
EXPECTED BEHAVIOR:
=================
Either:
1. add the option to specify a subvolume for a menuentry, and use relative paths from within the subvolume
(which would be benefitial, when i.e. booting some other [backup]snapshot. only the subvolume needs to be changed)
2. use full paths again (including the subvolume in the path)
additionally: automatically recognize linux-installations on other subvolumes
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