Comment 4 for bug 974284

16:58 < smoser> ie, to safeguard for the power failure case, where 5 minutes wasn't enough, but 5 minutes and 3 seconds would have been.
16:59 < stgraber> so we want dhclient to try for $TIMEOUT, if it gets a lease during that time, background itself and get into a renewal/retry loop, if it doesn't, then ???
16:59 < stgraber> for ??? I tend to prefer failing as I really don't want to run the ifupdown hooks unless we have a working connection
17:00 < stgraber> but you clearly prefer continuing regardless that'll make all the upstart jobs trigger as well as all upstart hooks (even though you don't have network access)

So to make this happen we'd need to patch isc-dhcp-client to add a new parameter (to avoid regressing -1 or the default mode) that essentially only triggers the initial wait for lease part of -1 but not the exit on failure to renew part.