#
# 2024-01-20
#
# Nice to find 'nsupdate' ... something I'd have liked to know of earlier, given the typical inability 
# of ISPs to lend an internet address for a nice, healthy, long time.
#
# This is an example (for running in a shell) of using 'nsupdate' (from bind-utils) to tell a running 
# named (bind, nameserver) to make a dynamic update to a zone. 
#
# It assumes that the /etc/named.conf (or equivalent file) defines a key for permitting 
# dynamic updates, such as 
#key keyname {
#        algorithm hmac-md5;
#    secret "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
#};
#
# The below will feed a list of commands into stdin for 'nsupdate', to remove an existing A-record for 
# a specified host (without failure if not pre-existing), and add a new one (with a 600 s TTL).

nsupdate  <<EOT 
server localhost 53
key keyname XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
zone example.org
update delete host.example.org. A 
update add host.example.org. 600 A 130.240.60.40
send
EOT

# If another zone is to be updated, this must be done in a separate invocation on nsupdate.
# For example, to update the corresponding reverse record:
nsupdate  <<EOT
server localhost 53
key keyname XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
zone 
zone 60.240.130.in-addr.arpa.
update add 40.60.240.130.in-addr.arpa. 600 PTR host.example.org.  
send