[PVE-User] Debian buster, systemd, container and nesting=1

Marco Gaiarin gaio at sv.lnf.it
Wed Feb 26 12:01:56 CET 2020


Mandi! Stoiko Ivanov
  In chel di` si favelave...

> > i can convert this container to an unprivileged ones, but other no, for
> > examples some containers are samba domain controller, that need a
> > privileged container.
> not sure - but why would a samba need to be privileged?

	https://lists.samba.org/archive/samba/2019-December/227626.html

samba, as AD Domain Controller, not as general 'share service', need
the use of 'SYSTEM' namespace, that in containers is reserved by root.
Indeed, if there's some 'caps' to relax that permit to use system
namespace with unprivileged containers, they are welcomed!


> > There's another/better way to make systemd work on containers?
> I guess my preferred actions in order:
> * setup new unprivileged container and migrate the workload/services from
>   the old one (optionally enabling nesting if needed)
> * try backup/restore to get a privileged container to an unprivileged one
> * keep the privileged container with nesting off
> * migrate the setup into a qemu-guest
> * edit the unit files of the affected services (e.g. apache) - usually
>   it's the PrivateTmp option which causes this (it wants to mount --rbind
>   -o rw /) - and drop the PrivateTmp option (see [0])
> * consider making an apparmor override for this particular mount
>   combination+container (which also can potentially be a security hole
>   (some apparmor rules are bound to absolute paths and using rbind you can
>   change the path)
> * turn on nesting for a privileged container (keep in mind that you then
>   open it up quite a bit for breakouts)
> of course probably not all of those options can be applied in your
> environment.
> [0]https://forum.proxmox.com/threads/apache2-service-failed-to-set-up-mount-namespacing-permission-denied.56871/

Mmmh... i'm a bit confused.

Firstly, it is not clear to me if nesting is needed because the
container is privileged, or privileged/unprivileged and nesting/non
nesting are property totally indipendent.

Second, in a PVE6 installation i've creared a debian buster container
(unprivileged, without nesting), installed apache and run correctly,
without tackling systemd units:

 root at vbaculalpb:~# systemctl status apache2
 ● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2020-02-26 11:35:29 CET; 15min ago
     Docs: https://httpd.apache.org/docs/2.4/
  Main PID: 1992 (apache2)
    Tasks: 54 (limit: 4915)
   Memory: 6.7M
   CGroup: /system.slice/apache2.service
           ├─1992 /usr/sbin/apache2 -k start
           ├─1994 /usr/sbin/apache2 -k start
           └─1995 /usr/sbin/apache2 -k start

 feb 26 11:35:29 vbaculalpb systemd[1]: Starting The Apache HTTP Server...
 feb 26 11:35:29 vbaculalpb systemd[1]: Started The Apache HTTP Server.
 root at vbaculalpb:~# systemctl show apache2 | grep PrivateTmp
 PrivateTmp=yes

This could lead to the answer to first question (nesting is needed only
for privileged containers), but also could lead to the fact that
container management could be diffierent between PVE5 (the original
request) and PVE6 (this test).


So, thanks for the answer but i hope in some more clue.

-- 
dott. Marco Gaiarin				        GNUPG Key ID: 240A3D66
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