Can't boot from a GRUB loop device.
The GRUB bootloader has the ability to boot directly from ISO images. `znx` exploits that feature to provide a very crucial part of its functionality. When a Manjaro image is deployed (GNOME, Plasma, XFCE), `znx` fails to boot it. The initramfs scripts will complain because the root device can't be found.
The [`miso_loop_mnt`](https://gitlab.manjaro.org/tools/development-tools/manjaro-tools/blob/master/initcpio/hooks/miso_loop_mnt) hook [tries to detect](https://gitlab.manjaro.org/tools/development-tools/manjaro-tools/blob/master/initcpio/hooks/miso_loop_mnt#L4) the loop device based on its label. However, the GRUB configuration file does not pass the needed parameter; instead, it passes the device UUID. But that UUID is never set.
A solution for that problem is to discover the device from within the initramfs by looking for the loop device (which is a file) in all the connected devices. That is achieved by the `find_dev_by_path` function below.
```shell
find_dev_by_path () {
local path="$1"
local tmp_mnt=/tmp_mnt
local _mnt
local a d
local device
[ "$path" ] ||
return 1
mkdir -p "$tmp_mnt"
for a in 1 2 3; do
for d in $(awk '{ print "/dev/"$4 }' /proc/partitions); do
# -- If the device is already mounted, it shouldn't be
# -- unmounted after the check.
grep -q "^$d " /proc/mounts && {
_mnt=$(grep "^$d " /proc/mounts | cut -d ' ' -f 2)
unmount=
} || {
mount -r -t auto "$d" "$tmp_mnt" 2> /dev/null || continue
_mnt="$tmp_mnt"
unmount=true
}
# -- File exists in $d. Save $d on $device.
[ -f "$_mnt/$path" ] &&
device="$d"
[ "$unmount" ] &&
umount "$tmp_mnt" 2> /dev/null || true
[ "$device" ] && {
echo "$device"
return
}
done
sleep 1
done
return 1
}
run_hook () {
[ "$img_flags" ] || img_flags="defaults"
if [ "$img_loop" ]; then
img_dev=$(find_dev_by_path "$img_loop")
mount_handler="miso_loop_mount_handler"
fi
}
miso_loop_mount_handler () {
newroot="$1"
local _dev_loop
msg ":: Setup a loop device from $img_loop located at device $img_dev"
_mnt_dev "$img_dev" "/run/miso/img_dev" "-r" "$img_flags"
if _dev_loop=$(losetup --find --show --read-only "/run/miso/img_dev/$img_loop"); then
misodevice="$_dev_loop"
else
echo "ERROR: Setting loopback device for file '/run/miso/img_dev/$img_loop'"
launch_interactive_shell
fi
miso_mount_handler $newroot
if [ "$copytoram" == "y" ]; then
losetup -d $_dev_loop 2> /dev/null
umount /run/miso/img_dev
else
echo $(readlink -f $img_dev) >> /run/miso/used_block_devices
fi
}
```
issue