A.1.2.2 version

Version of the server software returned in a response for the query for TXT record version.server. or version.bind. in the CHAOS class (see RFC 4892).

Option allows a boolean value on|off, if on, automatic version string is set as a default. If not specified or empty, the server returns REFUSED status code.

system {
  version "Knot DNS 1.3.0";
  version on; # Reports current version
}