The template configurations in the new ntpd subdir also address the
recent NTP amplification attacks that have been going on recently.

NTP configuration is controlled by a few defs-* variables:

NTPSERVER: boss|ops|fs|<external-server-name-or-IP>
  Default: "ops"
  Normally, one of boss, ops, or fs is designated as a local NTP server
  but this can be set to a fully qualified name of some other machine.
  If NTPSERVER is set to an external server, then boss/ops/fs are made
  clients of that server just as any testbed node is.

EXTERNAL_NTPSERVER[1-4]: <external-server-name-or-IP>
  Default: "[0-3].pool.ntp.org"
  If NTPSERVER is one of boss/ops/fs, then these values are used as the
  upstream servers for the local server. These can be changed to four of
  your favorite NTP servers.

NTPDRIFTFILE: <path>
  Default: "/var/db/ntp.drift"
  If NTPSERVER is one of boss/ops/fs, then this is the name of the drift
  file for the local server.