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Multiple Kerberos realms on single host

We are using Kerberos for central authentication at our university department; recently, we have set up a second realm for authentication to other services than UNIX logins (e.g. webmail) – we did not like the idea of reusing the same passwords.

Setting up a second realm has been pretty straightforward, just add the other realm to /etc/krb5.conf, write explicit port number to admin_server and kadmin_port options, add another init script for secondary admin server and… it almost works.

But suddenly, users find themselves unable to change their password within the original realm using passwd or kpasswd, with less than helpful Authentication error: Failed reading application request. And that’s the reason I’m writing up this, since you explicitly need to set the totally undocumented option kpasswd_port to a different value than 464! This is because kadmind provides the kadmin service on TCP port (749 by default), but also chpw service on UDP port (464 by default).

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