Passing "nowait" command line option to "dhclient"

[Steffen Dettmer <steffen.dettmer@gmail.com>]

Hi,

I configured several interfaces using ifupdown using DHCP by stanzas like:

auto eth2
  iface eth2 inet dhcp

When booting and one of the DHCP interfaces has no cable attached,
booting is delayed about around 60 seconds (seems to be value of
dhclient.conf:timeout). I think I have to pass the option "-nw" to
dhclient, but how do I do that correctly? Apparently the dhclient
invocation call is hardcoded in ifupdown, but surely I didn't
understand the C source code (which is generated by a generated source
code generator).

I noticed that DHCP leases are kept as long as the lease is valid when
moving from one LAN to another, not sure if this behavior is correct.
I considered ifplugd which solves both issues, but then all static
addresses of the interface are missing as long as no cable is plugged
(which might usually be expected on Desktops / Laptops, but might not
be desired on other devices, because it prevents from binding sockets
to specific IP addresses).

How to configure DHCP correctly without causing boot delays?

Regards,
Steffen