Bug#739593: systemd makes / shared by default (fwd)

[Tomas Pospisek]

(resubmitting/forwarding since on first attempt this bug was already
  archived and this my comment wouldn't get included therein)

---------- Forwarded message ----------
Date: Sun, 8 Feb 2015 18:19:06 +0100 (CET)
From: Tomas Pospisek
To: 739593 at b.d.o
Cc: Christoph Berg
     Michael Stapelberg
     Bastian Blank
     Sam Morris
     Martin Pitt
Subject: Re: systemd makes / shared by default

Hello all,

there's more fallout from the change of the default that makes bind mounts 
share submounts (as introduced by systemd) instead of the previous default that 
kept them private (as given by the linux kernel).

I have a variety of chroot systems that go like this:

   sudo mount --rbind /dev $CHROOT/dev
   sudo mount -t tmpfs tmpfs $CHROOT/run/shm

   # exec some not very much trusted app such as skype

   sudo umount -l $CHROOT/run/shm
   sudo umount -l $CHROOT/run
   sudo umount -l $CHROOT/dev

This worked under wheezy. Under jessie instead it wrecks havoc to the running 
system in that /dev/shm gets unmounted in the base (parent) system and so a lot 
of stuff stops working (such as my terminal application "konsole", system shut 
down/reboot, chromium etc. etc.).

<opinion>
I *think* that if Debian had a Linus type "benevolent dictator" that dictator 
would at this moment be on a spree to verbally kill people for breaking the 
system's API. I opine that unless the matter of API stability will be taken as 
seriously as Linus does there will be no "year of the Linux desktop" ever, 
since application writers can't be expected to be running around in circles all 
year long fixing "petty" API breaks left and right on every odd Linux 
distribution. And user's can't be expected to be rebuilding their systems from 
scratch and reinstalling all their (custom, proprietary, weird) software from 
new versions every few years just because the base system had an upgrade.
</opinion>

But aside from making my opinion known here, I am unable to offer a remedy 
apart from reverting the default, which would break other software, that 
depends on the *new* default behavior as set by systemd.

So unless someone has a clever idea, I'm just going to document this in the 
Debian wiki.

I think a warning in the release notes would also be appropriate.
*t