Restarting DHCP safely whilst avoiding partner-down state

[Marc Haber]

On Fri, May 13, 2016 at 02:00:03PM +0100, Terry Burton wrote:
> I'm attempting to write a systemd .service file for my own uses of ISC
> DHCP. However, if it can be made sufficiently generic then I would
> intend to push this upstream or at least into distributions.
> 
> It needs to be suitable for managing failover pairs and I'm struggling
> with the age-old problem of restarting a dhcpd instance. From reading
> around there does not currently appear to be a method for restarting
> dhcpd that is both *safe* and *useful* in such a setup.

Please also cover the IPv6 case. On my systemd systems, I do have an
isc-dhcp-server-v4 and an isc-dhcp-server-v6 service and an
isc-dhcp-server service that is WantedBy both -v4 and -v6, so that
both instances start up concurrently when one does systemctl start
isc-dhcp-server.

Greetings
Marc

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