pgsqldns is a DNS server based on the sqldns framework, reading from PostgreSQL tables.
Normally pgsqldns would be set up by the pgsqldns-conf program, but that program doesn't exist yet.
pgsqldns connects to a PostgreSQL server as specified by $PGHOST, $PGPORT, $PGUSERNAME, $PGPASSWORD, and $PGDATABASE. After connecting, it executes any commands found in $SQL_INITIALIZE.
See the sqldns documentation for full configuration details.