I installed dhcpd-server-3.0.1 out of ports.

Here is the defaults in /etc/rc.conf:

            dhcpd_enable="YES"                          # dhcpd enabled?
            dhcpd_flags="-q"                            # command option(s)
            dhcpd_conf="/usr/local/etc/dhcpd.conf"      # configuration file
            dhcpd_ifaces="xl0"                             # ethernet interface(s)
            dhcpd_withumask="022"                       # file creation mask

            dhcpd_chuser_enable="YES"                   # runs w/o privileges?
            dhcpd_withuser="dhcpd"                      # user name to run as
            dhcpd_withgroup="dhcpd"                     # group name to run as
            dhcpd_chroot_enable="YES"                   # runs chrooted?
            dhcpd_devfs_enable="YES"                  # uses devfs if available?
            dhcpd_rootdir="/var/db/dhcpd"               # directory to run in
            dhcpd_flags="-early_chroot"                 # needs full root

            dhcpd_jail_enable="YES"                     # runs imprisoned?

            dhcpd_hostname="ana-dhcp.csail.mit.edu"                 # jail hostname
            dhcpd_ipaddress="128.30.80.12"              # jail ip address


Here is the error that I get when I try to start it up:

v# /usr/local/etc/rc.d/isc-dhcpd.sh start
mkdir: /var/db/dhcpd/dev/_: Operation not supported
/usr/local/etc/rc.d/isc-dhcpd.sh: ERROR: unable to create directory /var/db/dhcpd/dev/_
v# 


Of course you can't make a directory there; it's devfs!

v# df
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/ad0s1a    253678    75702   157682    32%    /
devfs               1        1        0   100%    /dev
/dev/ad0s1e    253678     2652   230732     1%    /tmp
/dev/ad0s1f 115569274 93990084 12333650    88%    /usr
/dev/ad0s1d    253678    65368   168016    28%    /var
devfs               1        1        0   100%    /var/db/dhcpd/dev
v# 

Suggestions? Right now I'm going to turn off the jail...

Fix: 

http://www.freebsd.org/cgi/sendpr-code.cgi?dummy=1
http://www.freebsd.org/cgi/sendpr-code.cgi?dummy=1