Not using systemd
Is there a way to automatically rebuild the postfix .db files
when the corresponding configuration file changes?
Yes, you can use a "make" to do this.
Its explained in great detail here:
If you create a Makefile (which I have done) then can just do:
in /etc/postfix when you have changed a configuration file. Very handy.
I have also modified the script which starts Postfix to do a make
just in case. In file /etc/rc.d/init.d/postfix I added:
echo -n $"Starting postfix: "
make | grep -v 'Nothing to be done for'
### Commented out since done by the make above
### make_aliasesdb >/dev/null 2>&1
Perhaps surprisingly, you do always not have restart Postfix to make
the change come into effect. As explained here:
".db files are not read into memory [by the Postfix daemons] and
don't require reloading."