[pkg-lxc-devel] Bug#925899: lxc: Unprivileged containers fail to start after recent updates

[Pierre-Elliott Bécue]

Le dimanche 31 mars 2019 à 14:55:52+0200, intrigeri a écrit :
> Pierre-Elliott Bécue:
> > Cc-ing intrigeri: I'm reconsidering the /etc/lxc/default.conf setting
> > regarding apparmor.profile. Putting generated breaks many unpriv
> > containers as they have no apparmor.profile set in their configuration.
> 
> Considering kernel.unprivileged_userns_clone is disabled by default
> on Debian, IMO we should:
> 
>  - Optimize for the Debian defaults, i.e. privileged containers:
>     - Keep the settings we added recently in /etc/lxc/default.conf
>     - Replace "Suggests: apparmor" with "Depends: apparmor", because
>       the default config will create containers that fail to start
>       if the apparmor package is not installed.
> 
>  - Document how to use unprivileged containers on Debian. It's not as
>    if they were previously working fine by default and AppArmor broke
>    them — regardless of AppArmor, on current sid with the default
>    kernel settings and lxc.apparmor.profile = unconfined, trying to
>    start an unprivileged container fails in a very much user
>    unfriendly way:
>    
>      conf.c: chown_mapped_root: 3250 lxc-usernsexec failed: Permission denied - Failed to open tt
> 
>    That's a first usability stumbling block. The new
>    lxc.apparmor.profile default setting merely adds a second one.
> 
>    So I think README.Debian should document the need for
>    kernel.unprivileged_userns_clone=1 and for
>    lxc.apparmor.profile = unconfined

Yes and no, the issue is that we introduced a new problem which made the
unpriviledged containers of user having already set the kernel properly
not working either.

There is a tradeoff in your current solution, and I wonder if it is the
appropriate one.

I'm Cc-ing Antonio and Evgeni to get their POV.

>  - Take care of the Stretch→Buster upgrade path for unprivileged
>    containers, by mentioning in NEWS.Debian that previously working
>    unprivileged containers now need lxc.apparmor.profile = unconfined.

The apparmor.profile = lxc-container-default-cgns works too, but will
prevent systemd isolation features to work.

-- 
Pierre-Elliott Bécue
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It's far easier to fight for one's principles than to live up to them.