[systemd-devel] resolved and bind-mount of /etc/resolv.conf

[Lennart Poettering]

On Fri, 15.01.16 10:33, Igor Bukanov (igor at mir2.org) wrote:

> Hi,
> 
> currently if one runs systemd-resolved, then  /etc/resolv.conf should
> be symlinked to /run/systemd/resolve/resolv.conf . Is  it possible
> instead to add an option for resolved to bind-mount /etc/resolv.conf
> into the real file when it starts?
> 
> This way stopping or disabling resolved will not require to update the
> symlink and parallel installation of 2 resolvers is possible when the
> decision to use a particular one can be done at runtime with no
> changes in /etc.

Well, the logic is really supposed to be: if /etc/resolv.conf is a the
symlink, then resolved manages the file. If it is anything else, then
resolved *reads* that file. 

Given that I use NetworkManager daily on my laptop, for the WLAN
stuff, which will manipulate /etc/resolv.conf directly, this behaviour
is what allows me to use resolved with it. 

> I suppose I already can do with service ExecStartPost, ExecStart hooks
> for resolved, but this is rather hackish as I do not know if resolved
> updates the file in place (which is compatible with bind-mount) or via
> rename of a temporary (which is not).

resolved *never* touches /etc/resolv.conf itself. It will update
/run/systemd/resolve/resolv.conf atomatically however, via renames,
hence a bind mount of it would not work...

Lennart

-- 
Lennart Poettering, Red Hat