On Mon, 2012-10-22 at 02:53 +0200, Kay Sievers wrote:
On Sun, Oct 21, 2012 at 11:25 PM, Michael H. Warfield
<mhw(a)wittsend.com> wrote:
> This is being directed to the systemd-devel community but I'm cc'ing the
> lxc-users community and the Fedora community on this for their input as
> well. I know it's not always good to cross post between multiple lists
> but this is of interest to all three communities who may have valuable
> input.
>
> I'm new to this particular list, just having joined after tracking a
> problem down to some systemd internals...
>
> Several people over the last year or two on the lxc-users list have been
> discussions trying to run certain distros (notably Fedora 16 and above,
> recent Arch Linux and possibly others) in LXC containers, virualizing
> entire servers this way. This is very similar to Virtuoso / OpenVZ only
> it's using the native Linux cgroups for the containers (primary reason I
> dumped OpenVZ was to avoid their custom patched kernels). These recent
> distros have switched to systemd for the main init process and this has
> proven to be disastrous for those of us using LXC and trying to install
> or update our containers.
>
> To put it bluntly, it doesn't work and causes all sorts of problems on
> the host.
>
> To summarize the problem... The LXC startup binary sets up various
> things for /dev and /dev/pts for the container to run properly and this
> works perfectly fine for SystemV start-up scripts and/or Upstart.
> Unfortunately, systemd has mounts of devtmpfs on /dev and devpts
> on /dev/pts which then break things horribly. This is because the
> kernel currently lacks namespaces for devices and won't for some time to
> come (in design). When devtmpfs gets mounted over top of /dev in the
> container, it then hijacks the hosts console tty and several other
> devices which had been set up through bind mounts by LXC and should have
> been LEFT ALONE.
>
> Yes! I recognize that this problem with devtmpfs and lack of namespaces
> is a potential security problem anyways that could (and does) cause
> serious container-to-host problems. We're just not going to get that
> fixed right away in the linux cgroups and namespaces.
>
> How do we work around this problem in systemd where it has hard coded
> mounts in the binary that we can't override or configure? Or is it
> there and I'm just missing it trying to examine the sources? That's how
> I found where the problem lay.
A very long ways, yeah. That looks like it could be just what we've
been looking for. Just gotta figure out how to set that environment
variable but that's up to a couple of others to comment on in the
lxc-users list. Then we'll see where we go from there.
Many thanks!
Kay
Regards,
Mike
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