Mac OS X provides a one-stop command for viewing and setting several OS configuration items.  The systemsetup command is found at /usr/sbin/systemsetup.

Running the command:

man systemsetup

in the Terminal application will return a full listing of the options available in this command.  This script uses the systemsetup command to configure a target system to use a specified network time server.  The script, as written, is intended for use with The Casper Suite.  Replacing $4 with a static value or using another method of passing a value would be necessary if you are not using The Casper Suite.

#!/bin/bash
##### HEADER BEGINS #####
# scr_sys_setNTP.bash
#
# Created 20090627 by Miles A. Leacy IV
# miles.leacy@themacadmin.com
# Modified 20090627 by Miles A. Leacy IV
# Copyright 2009 Miles A. Leacy IV
#
# This script may be copied and distributed freely as long as this header
# remains intact.
#
# This script is provided “as is”.  The author offers no warranty or
# guarantee of any kind.
# Use of this script is at your own risk.  The author takes no responsibility
# for loss of use,
# loss of data, loss of job, loss of socks, the onset of armageddon, or any
# other negative effects.
#
# Test thoroughly in a lab environment before use on production systems.
# When you think it’s ok, test again.  When you’re certain it’s ok, test
# twice more.
#
# This script sets a Mac OS X system to use a network time server specified
# by the value passed in the $4 parameter by the Casper Suite.
# Run as an “at reboot” script when imaging with Casper, making sure to type
# double-check the serial in the script parameters before imaging.
#
##### HEADER ENDS #####
systemsetup -setusingnetworktime on -setnetworktimeserver $4
#!/bin/bash

##### HEADER BEGINS #####
# scr_sys_setNTP.bash
#
# Created 20090627 by Miles A. Leacy IV
# miles.leacy@themacadmin.com
# Modified 20090627 by Miles A. Leacy IV
# Copyright 2009 Miles A. Leacy IV
#
# This script may be copied and distributed freely as long as this header
# remains intact.
#
# This script is provided "as is".  The author offers no warranty or
# guarantee of any kind.
# Use of this script is at your own risk.  The author takes no responsibility
# for loss of use,
# loss of data, loss of job, loss of socks, the onset of armageddon, or any
# other negative effects.
#
# Test thoroughly in a lab environment before use on production systems.
# When you think it's ok, test again.  When you're certain it's ok, test
# twice more.
#
# This script sets a Mac OS X system to use a network time server specified
# by the value passed in the $4 parameter by the Casper Suite.
# Run as an "at reboot" script when imaging with Casper, making sure to type
# double-check the serial in the script parameters before imaging.
#
##### HEADER ENDS #####

systemsetup -setusingnetworktime on -setnetworktimeserver $4