[ale] Copying config files to DHCP peer

[Todor Fassl]

I have been running peered ISC dhcp servers for years. The problem is 
that you need copies of the config files on both machines. Say you want 
to assign an IP address to a new machine. You add a stanza to a config 
file but then you then have to get a copy of the modified config file to 
the peer. If you forget to do that, you are going to screw things up 
pretty badly.

Other people in my department occasionally need to make these config 
changes. So I need a way to guarantee that the config files get copied 
over. Googling showed me lots of articles on configuring a peer in 
isc-dhcp but only one on syncing the config files. That person was doing 
it via rsync and a script in cron.hourly.

What I have done, at least for now, is to replace the init script with 
my own script. This script uses an ssh key to copy the files to the peer 
and then restarts dhcp on the peer. If somebody types "service dhcp 
restart", it runs my script. But now with systemd, it is going to be harder.

Fortunately, for now, my co-workers are still typing "service bind9 
restart" and the like. So "service dhcp restart" is not a problem -- 
yet. But if somebody types "systemctl restart isc-dhcp-server", it is 
not going to work.


Its interesting that bind9 and slapd handle this under the covers.


-- 
Todd