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I don't have much experience working with NIS at all, as I came from an LDAP environment. I have a project to move a bunch of clients within a NIS domain to point at a new NIS master server. There's no config management in place, and no real authoritative list of every machine in the domain.

How do I verify that no NIS clients are talking to the old master? I don't see any ypserv log files (the old master is a RedHat AS 3 box...), and AFAIK there's no reliable way to tcpdump for NIS traffic since it uses RPC.

Any ideas?

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Jason, forgive me if this seems rude, but you've been a member for over two years, asked fourteen questions, and accepted the answer to only three. We see that as a big "30% accept rate" warning next to your name. You might want to go back and review some of your earlier questions; "ACCEPT" isn't just for perfect answers, but also for "the best of the bunch" - remember, if someone comes along later and posts some unexpected perfection, you can always change which one is ACCEPTed. – MadHatter Dec 1 '11 at 8:27
up vote 2 down vote accepted

Funnily enough, I was doing that just this morning, to verify that people were talking to my new NIS server.

Firstly, find the port that ypserv is on with

oldserver> rpcinfo -p|grep ypserv
    100004    2   udp    844  ypserv
    100004    1   udp    844  ypserv
    100004    2   tcp    847  ypserv
    100004    1   tcp    847  ypserv

Then, you can use tcpdump to look for traffic:

oldserver> sudo tcpdump -n -n port 847 or port 844
15:09:18.714526 IP > UDP, length 56
15:09:18.714679 IP > UDP, length 28
15:09:20.717203 IP > UDP, length 56
15:09:20.717296 IP > UDP, length 28
15:09:21.326160 IP > UDP, length 56
15:09:21.326225 IP > UDP, length 28

As you can see, my server ( is definitely getting traffic. If you don't see anything after a half-hour or so, you're not getting anything.

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Don't know why I didn't think of that. Thanks! – Jason Antman Dec 2 '11 at 15:15

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