Bug#845161: udev: "mount: invalid option --" when busybox is not installed

[Simon McVittie]

On Mon, 21 Nov 2016 at 10:16:50 +0000, Luca Boccassi wrote:
> The context is a squashfs and liveboot/build based ISO.
...
> I don't pick the mount utility in any of my scripts or configs, so I do
> not know when or where the change happened, could have been anytime
> since Jessie was released. But I am 100% sure that it's the util-linux
> one being used in this case, as proved by the fact that --move fixed the
> boot process.

I believe this was considered to be a bug in live-boot-initramfs-tools
(and its fork open-infrastructure-system-boot): l-b-i-t and o-i-s-b added
/root/bin to $PATH, causing the to-be-booted system's util-linux /bin/mount
to be used instead of the initramfs's busybox or klibc mount.
A kernel and initramfs-tools maintainer stated in
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=823856#20> that this
is not supportable - I believe his position was that every command must
either run in the initramfs with $PATH entirely from the initramfs,
or run chrooted into the to-be-booted system with $PATH entirely from
the to-be-booted system, but never a mixture of the two.

This was fixed as #823069 for l-b-i-t and as #832752 for o-i-s-b. Both
bugs were treated as having 'critical' severity.

> Of course as you all pointed out this won't work with klibc mount and it
> needs to be fixed. But please if possible don't revert, as it will break
> again virtual filesystem based images.

My understanding is that if you build your images
with live-boot-initramfs-tools (>= 1:20160511) or with
open-infrastructure-system-boot (>= 20160601-1), both of which are
available in testing, then reverting the udev change altogether
(consistently using mount -o move everywhere) should be harmless.

    S