topic Re: dns change in Operating System - HP-UX

dns change

Donald Thaler — Mon, 29 Mar 2010 09:38:54 GMT

if the dns server was changed what files other than resolv.conf would have to be changed ?

Re: dns change

Michal Kapalka (mikap) — Mon, 29 Mar 2010 09:42:21 GMT

hi,

if its on the client site only the

/etc/resolv.conf should be change.

mikap

Re: dns change

Bill Hassell — Mon, 29 Mar 2010 12:23:44 GMT

Use nslookup to verify the new server works OK:

nslookup somehost

This can (should) be done before you change resolv.conf so you can troubleshoot any problems without affecting the current settings.

Re: dns change

Donald Thaler — Mon, 29 Mar 2010 15:08:36 GMT

nslookup works.... are there any processes that might have to be stopped and started as a result of the dns change...we use opentext's(hummingbird) exceed xdmcp and we've noticed that of the six servers that normally show up int the xdmcp data manager chooser, only 1 was showing this morning. I rebooted another server and after a few minutes it also shows up in the xdmcp data manager window. i was hoping not to have to reboot my production server, but if there are no processes that need to be restarted i may have to reboot the other servers tonight.

Re: dns change

Bill Hassell — Mon, 29 Mar 2010 17:14:29 GMT

Changing DNS servers can be just as traumatic as changing IP addresses. There will be unexplained delays and failed connections until all the ARP tables expire in each system (server and client). And that assumes that the new servers have identical records to the old servers.

Re: dns change

Donald Thaler — Mon, 29 Mar 2010 17:23:34 GMT

so rebooting may be my only option if things haven't changed by 23:00pm ?

Re: dns change

Tingli — Mon, 29 Mar 2010 17:24:31 GMT

You need to flush the arp cache. You can look at:
http://forums13.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1269886992841+28353475&threadId=1127368

Re: dns change

rick jones — Mon, 29 Mar 2010 23:37:55 GMT

Bill - why do you say that changing /etc/resolv.conf to point at different DNS servers requires ARP cache changes?

I can certainly see where moving an IP address from one interface (MAC address) to another MAC address won't "take" for the other systems until their (or the router's) ARP cache is updated, but that is not the same thing as editing /etc/resolv.conf to point at different IP addresses serving-up DNS entries.

Re: dns change

Bill Hassell — Tue, 30 Mar 2010 01:12:19 GMT

Rick: why do you say that changing /etc/resolv.conf to point at different DNS servers requires ARP cache changes?

You're right of course. I have seen too many DNS server changes where the new servers were not in sync and some were given the same IP as the old servers creating an interesting combination of errors, some of which disappeared after ARP cache flushes.

Re: dns change

Donald Thaler — Tue, 30 Mar 2010 01:38:34 GMT

i flushed the arp cache, i can now see the new dns server in the cache, but it still hasn't solved my problem

Re: dns change

Matti_Kurkela — Tue, 30 Mar 2010 06:59:02 GMT

In HP-UX, each process will read /etc/resolv.conf once when starting up, and won't read it again later. This is probably done by the common startup code in libc, so just about all programs will have the same behaviour.

While a reboot might not be absolutely necessary when changing DNS servers, a restart of all long-running application processes would certainly be required.

MK

Re: dns change

bullz — Tue, 30 Mar 2010 07:29:10 GMT

Some times, u may need to restart inetd process.

ps -ef | grep inetd
kill -HUP

Re: dns change

Donald Thaler — Tue, 30 Mar 2010 10:31:19 GMT

Matti might have just 'hit the nail on the head', my exceed display manager selector was not displaying the unix servers, and by killing the dtlogin process and then restarting it my problem went away. I tried stopping it and restarting the dtlogin process but nothing worked until i actually killed the process