NSSYNC
	DNS Zone Files Maintenance Utility	Sergey Poznyakoff

2 Overview

The nssync utility is normally started periodically from crontab. Upon startup it reads its configuration file, which supplies the necessary program settings. Then, if the settings require so, it verifies that no other copy of the nssync is already running. Further on, it parses the named configuration file named.conf to determine several settings needed for its further operation, in particular, the value of the ‘directory’ statement in the ‘options’ block.

Once these preliminary operations are over, nssync starts its main task. Its configuration file defines, among other data, one or more synchronization blocks. Each such block defines SQL statements which return information about DNS zones as well as the location of named configuration file where the zone statements for these zones are to be stored (it is supposed that this file is included somewhere in the main named.conf file). For each synchronization block, the utility retrieves the zone data from the database and formats them into separate zone files. Each of these files is then compared to an already existing one (locations of the zone files are defined in the synchronization block they pertain to). If the files differ, new zone file replaces the old one and a flag is set indicating that the named daemon needs to be restarted in order to read new configuration.

When this stage is finished, nssync reloads the name server (if required) and exits.

Several command line options can be supplied in order to modify the program’s behavior. In particular, it is possible to check the configuration file syntax or even instruct the utility to do everything, except modifying the zone files (a so-called dry-run mode). This allows you to debug your configuration before actually starting using nssync.