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dns change

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Donald Thaler
Super Advisor

dns change

if the dns server was changed what files other than resolv.conf would have to be changed ?
12 REPLIES
Michal Kapalka (mikap)
Honored Contributor
Solution

Re: dns change

hi,

if its on the client site only the

/etc/resolv.conf should be change.


mikap
Bill Hassell
Honored Contributor

Re: dns change

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.


Bill Hassell, sysadmin
Donald Thaler
Super Advisor

Re: dns change

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.
Bill Hassell
Honored Contributor

Re: dns change

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.


Bill Hassell, sysadmin
Donald Thaler
Super Advisor

Re: dns change

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

Re: dns change

rick jones
Honored Contributor

Re: dns change

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.
there is no rest for the wicked yet the virtuous have no pillows
Bill Hassell
Honored Contributor

Re: dns change

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.


Bill Hassell, sysadmin
Donald Thaler
Super Advisor

Re: dns change

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

Re: dns change

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
MK
bullz
Super Advisor

Re: dns change

Some times, u may need to restart inetd process.

ps -ef | grep inetd
kill -HUP
Donald Thaler
Super Advisor

Re: dns change

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