Comment 5 for bug 1633619

Steve,
Good sleuthing.

Bug 974284 has good info in it.

This is definitely tricky.
I think we have the following cases to consider and may be at odds.
a.) dhclient -1 should exit failure as documented.
b.) we need a reliable point in boot where all static networking is configured.
c.) Ill timed reboot (or recovery from lab power failure)
    a system is configured for dhcp is rebooted while the dhcp server is unavailable.
    It seems better for this system to keep trying to get an IP address as otherwise
    the system will be offline forever.
d.) Any dhcp server downtime and failed lease renewal.
    a system is configured for dhcp and initially succeeds, but while re-trying a lease
    the dhcp server is down for scheduled maintenance. A failure to release here
    results in system offline if dhclient takes down the interface.
    This is mentioned at https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/838968/comments/11