root changing NIS passwords

[Mark Carroll <mark@chaos.x-philes.com>]

I've installed the Debian NIS stuff and it all works wonderfully for
regular users. However, /usr/share/doc/nis/nis.debian.howto.gz says that,

        "Root" can - using the root password - change other people's
        passwords, finger info and shell.

However, as root on my NIS master, I can't change my (markc's) password:

        # yppasswd markc
        Unknown error
        yppasswd: unknown user (uid=0).
        #

My /var/yp/Makefile has MINUID=1000 and MINGID=1000, which seem nice, and
/etc/nsswitch.conf has passwd: group: and shadow: as compat (although I
can't find documentation that tells me what compat means).

Am I just doing something dumb?

-- Mark