Linux – ny way to force the Linux box to always boot up with a self-assigned IP address

dhcpinterfacelinux

This is perhaps an unusual request: I'm trying to get a Debian Linux box to always give itself a self-assigned IP address (i.e. 169.254.x.y) on boot. In particular, I want it to do that even when there is a DHCP server present on the LAN. That is, it should not request an IP address from the DHCP server.

From what I can see in the "man interfaces" text, there is an option for "manual", and an option for "dhcp". Manual assignment won't do, since I need multiple boxes to work on the same LAN without requiring any manual configuration… and "dhcp" does what I want, but only if there is no DHCP server on the LAN. (A requirement is that the functionality of these boxes should not be affected by the presence or absence of a DHCP server).

Is there a trick that I can use to get this behavior?

EDIT: By "no manual configuration", I mean that I should be able to take this box (headless) to any LAN anywhere, plug in the Ethernet cable, and have it do its thing. I shouldn't have to ssh to the box and edit files to get it working each time it is moved to a different LAN.

Best Answer

If you install the avahi-autoipd package, and run it with the --force-bind option in a custom init or if-up.d script, you will always get a link-local address.

You can then use iface eth0 inet manual in your interfaces(5) file, although you will need to edit /etc/network/if-up.d/avahi-autoipd to add manual to the method lines.

There is more information about avahi-autoipd on the Avahi wiki.

Personally, I would edit /etc/network/if-up.d/avahi-autoipd to with something like:

--- avahi-autoipd       2010-08-04 04:26:49.000000000 +0800
+++ avahi-autoipd.1     2010-11-11 09:57:54.000000000 +0800
@@ -13,10 +13,13 @@
 esac

 case "$METHOD" in
-       static|dhcp|NetworkManager) ;;
+       static|dhcp|NetworkManager|linklocal) ;;
        *) exit 0
 esac

+if [ "$METHOD" == "linklocal" ]; then
+       /usr/sbin/avahi-autoipd --force-bind --daemonize --wait $IFACE 2> /dev/null
+fi

 if [ -x /bin/ip ]; then
        # route already present?

You can then list interfaces as iface eth0 inet linklocal. The edits to be made to the if-down.d script are left as an exercise to the reader.

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