name resolution puzzle

[Derek Ragona]

On 8/3/2018 4:41 PM, Valeri Galtsev wrote:
> Dear Experts,
>
> I just noticed some behavior of commands "host" and "nslookup" that 
> puzzles me. Namely, they do not query /etc/hosts file first, but query 
> nameserver instead, even though nsswitch.conf order is "files dns":
>
> $cat /etc/nsswitch.conf | grep hosts
>
> hosts: files dns
>
> $ cat /etc/hosts | grep holometer.uchicago.edu
>
> 128.135.20.84    holometer holometer.uchicago.edu
>
> $ host holometer.uchicago.edu
>
> holometer.uchicago.edu has address 128.135.52.70
>
> $ nslookup holometer.uchicago.edu
>
> Server:        128.135.249.50
> Address:    128.135.249.50#53
>
> Name:    holometer.uchicago.edu
> Address: 128.135.52.70
>
>
> So, it appears, that the commands "host" and "nslookup" go directly to 
> DNS server, and do not look into /etc/hosts first which I have expected.
>
> I should mention that other compiled programs do obey the 
> nsswitch.conf query order.
>
>
> Can someone enlighten me on this?
>
>
> The reason I have different IP in /etc/hosts is: I'm building the box 
> to migrate some host to, and I'd like to test some stuff that should 
> work from other machines before I switch DNS records to new IP. So, on 
> these external machines I am trying to have hostname resolve into 
> future IP just by adding it to /etc/hosts.
>
> Thanks.
> Valeri
>
Do a:

man 5 hosts

You have the wrong order in your /etc/hosts file

you have:
128.135.20.84    holometer holometer.uchicago.edu

Should be:
128.135.20.84    holometer.uchicago.edu holometer

Also try dig which is more current that nslookup.

-Derek

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