[systemd-devel] Shutdown root fs on loop device

[Michael Lipp]

Hi,

I have some PCs where I have to store the Linux root file system as a
large file in Window's NTFS file system. Everything boots fine. The NTFS
file system is mounted as ntfs-3g in the initial ramfs as /host, the
loopback device is created (using /host/Linux/image.img) and used as root.

However, the system doesn't shut down cleanly, usually it simply hangs.
I admit that it isn't easy to solve this situation on shutdown. When
executing findmnt in the running Linux system, the only "hint" is
/dev/loop0 being mounted as root. The NTFS mount doesn't appear at all.
It only shows in systemctl status, which starts with

init.scope
|.   1 /sbin/init
|- 155 mount.ntfs-3g -o permissions /dev/sda2 /host

Is it possible to configure systemd-shutdown somehow (e.g. hook
scripts)? Or do I have to write my own systemd-shutdown?

 - Michael