[systemd-devel] /etc/resolv.conf link in container

[David Herrmann]

Hi

On Tue, Jun 16, 2015 at 11:39 PM, Johannes Ernst
<johannes.ernst at gmail.com> wrote:
> I have a root filesystem in directory foo/
> It has symlink
>     foo/etc/resolv.conf -> /run/systemd/resolve/resolv.conf
>
> When I’m booting the container:
>     sudo systemd-nspawn --directory foo --boot
>
> I’m getting:
>     Failed to copy /etc/resolv.conf to /home/…./foo/etc/resolv.conf: Too many levels of symbolic links
>
> This message makes very little sense to me. Why is a copy necessary? and is that indeed /etc/resolv.conf or foo/etc/resolv.conf?
>
> If I boot with -n, I don’t seem to get the error.

If you pass --private-network / -n, then we never touch resolv.conf.
In all other cases, we copy resolv.conf from the host into the
container. We usually assume that if your container runs in the same
network as the host, then the container must also use the DNS features
of the host.

The error code of "Too many levels of symbolic links" is ELOOP. This
is returned by open() in many cases. In this example, it is returned
because we passed O_NOFOLLOW to open(), but the final part of the path
is a symlink. In that case, the kernel returns ELOOP to tell us that
we're dealing with a symlink.

Maybe Lennart or Tom have some comments on that? Your example use-case
(resolved in the container, even with shared network namespace) looks
valid, though odd. I mean, what's the reason not to use "-n"? Anyway,
maybe we can deal with ELOOP in setup_resolv_conf() and just print a
big fat warning?
But lets people who know that stuff comment first..

Thanks
David