Wake on LAN: No safe way to keep interface up

[Heike C. Zimmerer]

Binary package hint: ifupdown

There should be a safe way to prvent an interface from being shut down when the system goes down, as it is sometimes needed for it to stay up in order to accept Wake On LAN requests.

This can currently already be achieved by "pre-down false" in the interfaces file (since a false result aborts), but the man page says this behaviour is not guaranteed for future versions.

[Erwan Hamon (erwan-hamon)]

This is a duplicate of https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/44170

I suggest importance to be raised since at my work, not being able to turn on the PC remotely with wake on lan is a major problem.

[Erwan Hamon (erwan-hamon)]

After some tests, "pre-down false" is not a workaround for me. I still have the problem even though ifupdown is not bringing down the interface. The computer is deaf to wake on lan magic packet after ubuntu shutdown.

I therefore suspect thet ifupdown may not be the (only) package concerned.

FYI, everything was working properly under Edgy. Problem appeared for me after upgrading to Feisty.

[Erwan Hamon (erwan-hamon)]

Sorry, duplicate was https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.10/+bug/26266

[Alan Jenkins (aj504)]

Ooo, thanks for posting this hack ("pre-down false"); it's much smaller than mine (rewriting init scripts).

I'd add that ideally you should remove the -i option to halt in /etc/init.d/halt - at the moment there is apparently a bug that stops halt -i working on ubuntu, but it's supposed to shutdown all network interfaces (see #127010).

For sleep/hibernate, you also need to stop it unloading network modules in /etc/acpi/suspend.d/70-modules-unload.sh

hibernate + wake-on-lan + ssh + screen = teh win.

[Jean Christophe André (progfou)]

FYI, on my side I ensure the interface stays "awaken" (and not up, it can not stay "up", in the Unix meaning of this term, once the system has shut down) by putting these two lines in /etc/default/halt :

NETDOWN=no # to not shutdown the interfaces
ethtool -s eth0 wol g # to activate the wake-on-lan facility

Best regards, J.C.