Bind, force zone update on slave

Late reply to your unanswered question:

Is it possible to force zone update from/on slave?

I just wanted to speed up/force a transfer and used this on my slave for each outdated domain:

rndc retransfer domain.com

Your setup is doing what it's supposed to do:

1. You modify a zone file, including updating the SOA serial.
2. You run rndc reload on master.
3. Master sends notify/notifies on zone change.
4. Slave(s) requests zone transfers.

BIND is not monitoring file changes i.e. it's normal that it doesn't do this automatically. You must run rndc reload on the master after every modification. A slave cannot force the master to reload configuration / zones.