topic Re: Name resolution question in Operating System - HP-UX

Name resolution question

Santos Vega — Mon, 03 Oct 2011 06:35:31 GMT

Hi all,

I want a system only resolves by files, so I have left "/etc/nsswitch.conf" as below:

hosts:files

When I nslookup as root , the behaviour is the expected: "Using /etc/hosts on: ...". But, when I try with another user it reads "/etc/resolv.conf", because it resolves by DNS, not by files as stated in "/etc/nsswitch.conf" . What can be the reason for this?

Regards,

Re: Name resolution question

Matti_Kurkela — Mon, 03 Oct 2011 06:43:37 GMT

Perhaps your /etc/nsswitch.conf is not readable by that user?

Re: Name resolution question

Santos Vega — Mon, 03 Oct 2011 06:56:21 GMT

Hi,

Yes, it was not readable (600 permissions). What I did was rename "/etc/resolv.conf". Now "/etc/nsswitch.conf" is 444, but my question is: If user cannot read "/etc/nsswitch.conf" , why does it resolve by DNS and not by files?

Regards,

Re: Name resolution question

Matti_Kurkela — Mon, 03 Oct 2011 09:49:04 GMT

If the process cannot read /etc/nsswitch.conf when it starts up, it uses HP-UX built-in defaults, which for IPv4 hostname resolution are: first DNS, then NIS, then files = /etc/hosts. If DNS or NIS reports that a host does not exist, next sources are not tried (i.e. [NOTFOUND=return] is in effect). This is documented in the nsswitch.conf man page.

For IPv6-aware processes on 11.23 and newer, the "ipnodes" line in /etc/nsswitch.conf is typically used instead of "hosts" - even for looking up IPv4 hostnames. The defaults for "ipnodes" omit NIS, but are otherwise identical to the defaults of "hosts".

At least on 11.23, the man page says: "The library functions contain compiled-in default entries that are used if the appropriate entry in nsswitch.conf is absent or syntactically incorrect" but in fact the defaults will also be used if /etc/nsswitch.conf is not readable for any reason.

Re: Name resolution question

Santos Vega — Mon, 03 Oct 2011 12:11:05 GMT

Ok, thank you very much for your help !

Regards,