>> 	then, you at least need to check if the machine is running NIS or not,
>> 	and suppress getdomainname() case if NIS is running.  IMHO.
>
>No, not really.  Half the time the NIS domain is the same as the DNS
>domain, and the rest of the time you have to set $mydomain anyway so
>it's never a loss (the $mydomain setting overrides in all cases).

the nis domain name is stored, for nis purposes, by setdomainname().

a host's domain name, for dns purposes, is usually stored in
/etc/resolv.conf.

a host's domain for mail purposes is usually the dns domain name,
unless overriden in whatever configuration files your mua/mta reads.

a host's kerberos realm is stored in yet another file.

most things fall back to dns (for mx records, or srv records, etc)
unless told otherwise.  no one falls back on nis.

fwiw - i have no idea why nis gets kernel help for its dirty work.

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