NO_PURGE indicates that records should not be deleted from a domain. Records will be added and updated, but not removed.
NO_PURGE is generally used in very specific situations:
  • A domain is managed by some other system and DNSControl is only used to insert a few specific records and/or keep them updated. For example a DNS Zone that is managed by Active Directory, but DNSControl is used to update a few, specific, DNS records. In this case we want to specify the DNS records we are concerned with but not delete all the other records. This is a risky use of NO_PURGE since, if NO_PURGE was removed (or buggy) there is a chance you could delete all the other records in the zone, which could be a disaster. That said, domains with some records updated using Dynamic DNS have no other choice.
  • To work-around a pseudo record type that is not supported by DNSControl. For example some providers have a fake DNS record type called "URL" which creates a redirect. DNSControl normally deletes these records because it doesn't understand them. NO_PURGE will leave those records alone.
In this example DNSControl will insert "" into the zone, but otherwise leave the zone alone. Changes to "foo"'s IP address will update the record. Removing the A("foo", ...) record from DNSControl will leave the record in place.
D("", .... , NO_PURGE,
The main caveat of NO_PURGE is that intentionally deleting records becomes more difficult. Suppose a NO_PURGE zone has an record such as A("ken", ""). Removing the record from dnsconfig.js will not delete "ken" from the domain. DNSControl has no way of knowing the record was deleted from the file The DNS record must be removed manually. Users of NO_PURGE are prone to finding themselves with an accumulation of orphaned DNS records. That's easy to fix for a small zone but can be a big mess for large zones.
Not all providers support NO_PURGE. For example the BIND provider rewrites zone files from scratch each time, which precludes supporting NO_PURGE. DNSControl will exit with an error if NO_PURGE is used on a driver that does not support it.
There is also PURGE command for completeness. PURGE is the default, thus this command is a no-op.
Last modified 17d ago