[lxc-devel] [Lxc-users] pivot root failures when "/" is mounted as "shared"

[Michael H. Warfield]

Additional comments specific to the pivot root issue...  Adding the
developers list as well, since this is a development issue...

On Sat, 2012-11-03 at 12:01 +0100, Peter Simons wrote:
> Hi guys,

> I've been using lxc for a while now, and it's a great tool. Thank you
> very much for the time and effort you have been dedicating to the
> development of that software!

> My Linux distribution (NixOS) is about to switch from upstart to
> systemd, and it this switch in the host system is going to break all my
> containers. It appears this is a well known problem that's been reported
> at

>   http://sourceforge.net/tracker/?func=detail&aid=3559833&group_id=163076&atid=826303

> and

>   https://github.com/lxc/lxc/issues/4.

> Now, I wonder what the status of this issue is. Is it clear how that
> problem can be remedied? Is there maybe a patch that fixes this problem?
> Does anyone know a work-around that I could use to keep my containers
> running when that switch to systemd occurs on the host system?

This was from another threat with the systemd guys.

On Mon, 2012-10-22 at 16:11 +0200, Lennart Poettering wrote:
> Note that there are reports that LXC has issues with the fact that
> newer
> systemd enables shared mount propagation for all mounts by default
> (this
> should actually be beneficial for containers as this ensures that new
> mounts appear in the containers). LXC when run on such a system fails
> as
> soon as it tries to use pivot_root(), as that is incompatible with
> shared mount propagation. The needs fixing in LXC: it should use
> MS_MOVE
> or MS_BIND to place the new root dir in / instead. A short term
> work-around is to simply remount the root tree to private before
> invoking LXC.
> 
> Lennart

> -- 
> Lennart Poettering - Red Hat, Inc.

So there you have a suggested workaround for the shared mount
propagation problem, which is what you are referring to.

ITMT...

Daniel, Serge?

Any thoughts on those comments vis-a-vis the pivot function and using
MS_MOVE or MS_BIND instead?  IIRC, we switched to pivot_root() years ago
to deal with some other issues that were plaguing us.

> Take care,
> Peter
> 
> 
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
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