Can DHCP deamon expire leases "lazily"?

[Tim]

On Tue, 2012-07-03 at 07:37 -0400, Tom Horsley wrote:
> I've got some virtual machines with old kernels that know nothing
> about virt clocks. They keep time so horribly when loaded up with
> testbed runs that they forget to renew their DHCP lease, which
> results in their name being removed from the DNS server, which
> results in testbed failure :-(.

If they keep time so badly, you might want to play around with NTP
servers forcing the clock back into sync, quite often.

> Does anyone know if it is possible to configure the DHCP daemon
> to just leave expired leases active until it actually needs
> to reuse the IP address for a new request?

Depends which daemon you're using, but that's sometimes the default
behaviour (completely new requests from strangers often get un-used IPs,
until it has no choice but to re-use previously leased ones, even if the
leases have expired).

One option is to extend the lease time to something much longer than the
expected up-time of those clients (a day, a few days, a couple of weeks,
et cetera).

Setting static addresses in the DHCP server configuration is probably
the simplest solution.  If you have less machines than available IPs,
I'd do that.  It also makes other configuration easier (firewalls, and
other networking), which machines always have the same IP.

-- 
[tim at localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

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