> To use the single user mode I press the space key
> and at the boot prompt I enter boot -s.
> This is no problem. But I canīt get any
> editor to change the setting in the dhcpd conf and rc.conf.
> vi or nano is not working.
>
> For example: When I type in vi /etc/dhcpd.conf
> The result is: vi: not found
>

After booting in single user mode, only the root partition is mounted, and
it is mounted read-only; unfortunately "vi" is under "/usr": so you must
mount it before use the editor.
After booting in single user do:

  # fsck -y /               (check F.S. before mounting "/" rw)
  # mount -u /              ( remount "/" rw )
  # fsck -y /usr            (check F.S. before mounting "/usr" rw)
  # mount /usr

  # TERM=vt100
  # export TERM                (set TERM var. needed by vi)

then you should be able to edit your config. file: disable the dhcpd.

The next test, please start dhcpd at shell prompt (with flag -f and -d )
and loook at the messages: mine (using your dhpcd config file) looks like
this:

root@netbsd:/etc# dhcpd -f -d
Internet Software Consortium DHCP Server V3.0.1rc11
Copyright 1995-2003 Internet Software Consortium.
All rights reserved.
For info, please visit http://www.isc.org/products/DHCP

** You must add a ddns-update-style statement to /etc/dhcpd.conf.
   To get the same behaviour as in 3.0b2pl11 and previous
   versions, add a line that says "ddns-update-style ad-hoc;"
   Please read the dhcpd.conf manual page for more information. **

If you did not get this software from ftp.isc.org, please
get the latest from ftp.isc.org and install that before
requesting help.

If you did get this software from ftp.isc.org and have not
yet read the README, please read it before requesting help.
If you intend to request help from the dhcp-server@isc.org
mailing list, please read the section on the README about
submitting bug reports and requests for help.

Please do not under any circumstances send requests for
help directly to the authors of this software - please
send them to the appropriate mailing list as described in
the README file.

exiting.
---------------------

As you can see, there is an error at the beginning of the messages.
Is it like yours ? In any case send me the complete output.

e-mail roberto.trovo [at] redix.it