[lxc-devel] Questions about lxc.autodev

[vivo75 at gmail.com]

Il 26/11/2014 22:35, Stéphane Graber ha scritto:
> Hello,
>
> So I'm looking into how to rework lxc.autodev to apply properly to all
> the cases we care about:
>  - Privileged containers started by root
>  - Unprivileged containers started by privileged root
>  - Unprivileged containers started by unprivileged root
>  - Unprivileged containers started by unprivileged user
>
> My understanding is that autodev currently creates /dev/.lxc and then
> uses one directory per-container+lxc-path-hash under there, creates the
> devices nodes and uses that as the container's /dev.
>
> My question is why the /dev/.lxc directory to begin with, wouldn't
> it make more sense to use LXC_PATH/<container>/dev, mount a tiny
> tmpfs on that and then use it? This would have the advantage of having
> the same path for privileged and unprivileged containers and avoid the
> ugly lxcpath hash.
>
>
> I believe the following setup would make a bit more sense and offer a
> consistent behaviour:
>  - If not available or not a tmpfs, create LXC_PATH/<container>/dev and
>    mount a tiny tmpfs on it. Chown the path to the container's root uid/gid
>    and chmod to something sane.
>  - For all the nodes we care about, attempt to mknod them in there, on
>    failure, fallback to touch+bind-mount from real /dev.
>
> This would allow for the exact same code to be used for all 4 cases, for
> the layout and location of the autodev tree to be entirely guessable
> without requiring fancy hashing (making it easier for external tools to
> interact with the autodev tree).
>
> As with the current implementation, the tree wouldn't be flushed on
> container reboot but it would on container shutdown.
>
>
> Does the above make sense or am I missing something about the design of
> current autodev?
>
> Cheers
>
it make sense and avoid the case where /dev is re-mounted and lxc is
then confused

the only potential benefit I see (w/o knowing lxc code) in using
/dev/.lxc/ is hardlinking betweeen /dev and /dev/.lxc/container/

Regards,
Francesco R.