[RFC] Automated generation of /etc/resolv.conf from the rc.d script

[John Baldwin]

On Thursday 24 April 2008 02:51:29 pm Ulrich Spoerlein wrote:
> On Thu, 24.04.2008 at 08:21:40 -0400, John Baldwin wrote:
> > On Monday 14 April 2008 11:44:13 am Eygene Ryabinkin wrote:
> > > At last, I did the needed modifications: patches against 7.0 from
> > > yesterday, April 13th, are attached.  The first one enables the
> > > creation of /etc/resolv.conf from rc.conf variables and the second
> > > brings the named forwarders rewriting using values obtained via
> > > DHCP.  I had touched dhclient-script, but it was really needed,
> > > because it is not good to have simular functionality in /etc/rc.d/resolv
> > > and in the dhclient-script.
> > >
> > > I decided not to cope with modifications of /etc/namedb/named.conf,
> > > but rather to create other file, /etc/namedb/named.forwarders.conf,
> > > that should be included from the main configuration.
> > >
> > > I am living for two days with this configuration (DHCP + local named
> > > instance) and no problems were spotted yet.
> > >
> > > Testing and feedback are more than welcome.
> > 
> > You can already override the domain name and DNS servers (including either 
> > overriding, providing a default, or prepending or appending to the list) 
via 
> > setings in /etc/dhclient.conf, so I don't think new rc.conf variables for 
> > that would be warranted.  Updating named.conf to forward is a neat idea.  
> > Howver, on my laptop on HEAD I've ended up just running nscd instead of a 
> > local DNS server and doing a 'nscd -I hosts' when I get a new lease to 
flush 
> > the host cache.  When I get to my laptop I'll post my bits of 
> > dhclient-exit-hooks and dhclient.conf to make this work.
> 
> People always forget, that a computer can get an IP address via ppp(8),
> too. That's why I'm (still) running a local bind and have hooks to
> update the forwarders + reload in dhclient-enter-hooks *AND* ppp.linkup.

nscd will work fine with ppp as well. :)  You would just need to invoke 
nscd -I hosts when you get a new lease there as well.  A lot easier than 
rewriting named.conf and reloading named.

> I'd say that nscd(8) is the way to go for 7.0 and up (though I still
> haven't set it up for myself ....)

Yes, and new patches would likely be going into 8.0 where nscd is already 
present. :)  Setting up nscd for caching DNS is literally the 2 lines I 
mentioned in my previous e-mail:

- nscd_enable="YES" (rc.conf) (plus manual start via /etc/rc.d/nscd if you
  don't want to reboot)
- add "cache" for the "hosts" line in /etc/nsswitch.conf

Having dhclient auto-invalidate the cache on a new DHCP lease is an optional 
feature. :)

-- 
John Baldwin