axfr does zone transfer from a remote dns server
zonefresh.rc is a script that tries to format axfr's
output nicely as a plan9 NDB file to sttandard output.

zonefresh has one option, -s which causes it to write its output
to /lib/ndb/sec.domain.dom, taking care not to truncate the file if
the zone transfer fails.

This is typically used to keep a local ndb file for a remote
dns server up to date so we can provide a seccondary dns service

run from cron as:

15 5 * * *	cpu		zonefresh  -s ns.domain.dom domain.dom