Slashdot Mirror
Standby TVs Waste Electricity, How About ACPI?
twitter asks: "There's power management and there's standby, do you know the difference? The BBC is running story on how much electricity is wasted by TV standby mode. Thanks to the very useful EnergyStar program, I'd be the one in seven who thought they were saving electricity, with the standby button. I've been very happy with APM and hibernation on laptops, and want to do something similar with the desktops I use. What's the state of APM / ACPI Wake-on-LAN for Linux these days?" Slashdot touched on this issue, earlier in the week, but that article was more on TVs, not on computer power saving technologies.
Sending the 'magic packet' is not difficult, and there is a variety of tools that can do this, including a ready made perl script, on a gentoo system, type 'emerge wakeonlan'.
The packet in question requires access to Layer 2 of the OSDI model, i.e. the ability to send raw ethernet packets. By way of an example, the Java security model traditionally forbade this sort of thing [Java doesn't even let you send ICMP packets at Layer 3, so there's no such thing as "PING" or "TRACERT" in Java].
If there is a vanilla plain-jane non-souped-up installation of a Perl interpreter that allows you access to Layer 2, then it's going against the Java security model.
Of course, obviously Perl != Java, but it's something to think about.
Along those lines, you might consider this recent discussion at /.:
Just like keyboard sniffing, if a Perl app has the ability to send a packet at Layer 2, then it's easy to surmise that it might be able to receive a packet at Layer 2, and from that it's easy to fear that it might be able to receive all packets at Layer 2, i.e. it's not so difficult to imagine that a Perl app could function as an ethernet sniffer.Anyway, just something to think about.