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,
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
named configuration file where the
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
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