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Bug#412249: please install resolvconf by default

reassign 412249 gnome-system-tools
retitle 412249 network-admin: desktop users are unable to use DHCP with static DNS
severity 412249 grave

On Sat, Feb 24, 2007 at 10:13:59PM -0000, peter green wrote:
> > Unfortunately, adding good DNS via network-admin doesn't archieve the same
> > effect, because dhclient will overwrite /etc/resolv.conf whenever 
> > it's run
> the most obvious question would be why doesn't network-admin know this and do something about it?

It can't really do anything.  network-admin relies (through ifupdown, I guess,
but that doesn't matter) on dhclient for DHCP setup.  All it can do is
fighting over with dhclient for /etc/resolv.conf, and it will always lose,
because the way DHCP works, it can re-run arbitrarily at any time.

> > which is going to be quite often if you happen to run 
> > network-manager (also
> > enabled by default).  This means Joe had to reload his DNS every 
> > 10 minutes
> > untill his friend Robert could debug the problem and figure out 
> > that resolvconf
> > was needed.
> what exactly does resolvconf do? does installing it alter the behaviour of the dhcp client or will they just fight over resolv.conf?

resolvconf's purpose is precisely to avoid the problem of two or more system
components fighting over that file.  It stablishes a new interface to add your
DNS stuff, and modifies behaviour of dhclient to learn about it.

I've been re-analising the problem.  Just installing resolvconf is NOT the
right way to fix this (sorry!).  It seems that due to circumstances I
haven't looked into, network-admin + resolvconf is able to override
dhclient's decisions where network-admin without resolvconf wasn't.  Don't
hold your breath though, just running "resolvconf -u" (which is something
that all resolvconf clients will be doing) will bring back dhclient's
unwanted DNS from /etc/resolvconf/.

To summarise, if we don't use resolvconf, network-admin modifies
/etc/resolv.conf and its changes are inmediately overriden by dhclient.  If
we use resolvconf, it *inmediately* works but it's just a matter of time
when it'll break again.

As to what network-admin can do, it could easily alter the order (run
dhclient first, then modify resolv.conf), but that would only archieve
temporary unfuckage (i.e., same situation as if resolvconf was installed).

Looking at dhclient-script, I've found there are enter and exit hooks

Perhaps network-admin could take advantage of those to prevent dhclient
from modifiing either resolv.conf or the corresponding file in resolvconf
database ?

Robert Millan

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