how do we update dns zone file entries without restarting named demon
probably send it SIGHUP to reload conf. kill -HUP <pid>
There's a utility to do that. It's called rndc.
rndc reload zone_name
This will load the updated zone.
Correct me if I'm wrong, I've never had to do this. But I would imagine a "service named reload" would do what you're wanting.
Yes, service command would not only load the zone files, but also will reload config files like named.conf etc. rndc utility is not only for loading the zone it's very useful when it comes to administering DNS. You can do zone transfer with this and many more, check man rndc for more info. Suppose you have updated just a host record on the forward and reverse lookup zones, you do not need to restart the whole service for that.
By the way, if you do not want even a small interruption to the named service, you will do the rndc way rather than the service way. For production systems, it matters.
Thanks all for your help !
And the term "rndc" is new for me... Let me take a look on this ...