[lug] Debian App DNS Issues

[Nate Duehr]

John Starkey wrote:
> In both Etch and Lenny I've had issues with only a few apps not being 
> able to perform DNS lookups. To date I think it's only been Eclipse 
> based apps, Firefox and Thunderbird. If I add an entry to my hosts file 
> they work fine. Iceweasel and Icedove and any other app out of the 
> repositories work fine.
> 
> A few months ago I ran across a post that mentioned a package that fixed 
> the problem.  I swore I bookmarked the post but I can't find it 
> anywhere. Does anyone happen to know what that package is? Google has 
> nothing in any of the terms I can think of to search with.

Is this a mobile machine, or does it stay on the same network?  DHCP or 
static?

Ultimately, whatever is in /etc/resolv.conf and /etc/nsswitch.conf are 
controlling what the DNS resolver on the system is going to give to 
applications running on it.

DHCP can be problematic on Linux because many of the DHCP clients mess 
with /etc/resolv.conf

The Debian "resolvconf" package *tries* to make some sanity out of all 
of this, but as Sean mentioned, it often just gets in the way of an 
admin/system owner who knows what they're doing.

I'm curious what IP address your system is trying to resolve from... 
I've seen some DHCP servers in cheap SoHo routers hand out their own 
internal address and then try to proxy DNS requests for all the 
"internal" machines that REALLY suck, performance-wise, and sometimes 
they're just flat-out broken.

Neat *idea* by the router folks, but ultimately putting the ISP's DNS 
server IP's into /etc/resolv.conf directly and just letting the router 
do it's normal job of just doing NAT, works just fine, and has for two 
decades now.

Boil it down to basics.  When it breaks, see if /etc/resolv.conf is 
correct.  If it's not... that's the troubleshooting target to hunt down.

Nate