DNS client - what exactly it is

UNIX Solaris
1

Hi all,

I always thought DNS server = provide DNS response (host to ip / ip to host) to DNS client (which send DNS resolve request).

So in my solaris 10 box, i setup /etc/resolv/conf, /etc/nsswitch.conf (added in dns) etc.

Yes, i am able to dig and nslookup. But.. am i a DNS client ?

svcs -a | grep dns
disabled svc:/network/dns/client:default
disabled svc:/network/dns/server:default

================================

DNS client service is disabled and yet i am sending DNS request to be resolved successfully.

Am i a DNS client ? what does the DNS client service actually does ?

Confused Noob.

2

nslookup is indeed a DNS client but your Solaris box might not be configured as a DNS client, i.e. doesn't resolve names through the DNS service.

For example if this command doesn't work, you would enable the dns client service:

ping www.unix.com

Are you sure you are running Solaris 10 and not Solaris 11 ?

1 Like
3

I have never bothered about the svc:/network/dns/client:default
In fact it is disabled on most Solaris 10 boxes; not needed.
It is not a service, just a status that can be used as a requirement for other services.

# svcs -l svc:/network/dns/client:default
fmri         svc:/network/dns/client:default
name         DNS resolver
enabled      false
state        disabled
next_state   none
state_time   Sat Sep 26 19:26:57 2015
restarter    svc:/system/svc/restarter:default
dependency   require_all/none svc:/system/filesystem/minimal (online)
dependency   require_all/none svc:/network/service (online)
dependency   require_all/none file://localhost/etc/resolv.conf (online)
dependency   require_any/error svc:/network/loopback (online)
dependency   optional_all/error svc:/milestone/network (online)

The following does the libc host resolving (just like ping, but without doing a ping)

getent hosts www.unix.com
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4

Yes, you are right. I just checked on Solaris 10 machine configured with DHCP and being a DNS client and the dns/client client is nevertheless reported as disabled.

# cat /etc/resolv.conf
nameserver 212.27.40.240
nameserver 212.27.40.241
# grep "^hosts"  /etc/nsswitch.conf
hosts: files dns # Added by DHCP
# getent hosts www.unix.com
4.59.125.171    www.unix.com
# svcs dns/client
STATE          STIME    FMRI
disabled       23:18:38 svc:/network/dns/client:default
# cat /etc/release
                    Oracle Solaris 10 1/13 s10x_u11wos_24a X86
  Copyright (c) 1983, 2013, Oracle and/or its affiliates. All rights reserved.
                            Assembled 17 January 2013
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5

Hi jlliagre, MadeInGermany,

Yea.. thanks for your advices.

That's precisely where I am confused. The use of this DNS client service. Seems pretty redundant ?

I am thinking if this is turn on, maybe DNS caching will take place ?

Hmm.

Regards,
Noob

6

No it won't have a practical effect.
The nscd service does host caching:

svcs svc:/system/name-service-cache:default
nscd -g | awk '$1=="CACHE:" {if ($2=="hosts") p=1; else p=0} p>0'
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