Wake-on-LAN with BusyBox?

Question

Is it possible to implement the wake-on-lan magic packet in bash? I'm using a old, customized BusyBox and don't have ether-wake. Is it possible to replace it with some other shell command, like:

wakeonlan 11:22:33:44:55:66

[wakeonlan](http://gsd.di.uminho.pt/jpo/software/wakeonlan/), although it seems to require perl which probably isn't in your busybox. — jw013, Feb 10 '12 at 15:36
if you are able to use `python` see http://code.activestate.com/recipes/358449-wake-on-lan/ and put `alias` for this in your `.bashrc` — harish.venkat, Feb 10 '12 at 19:38
Since BusyBox has a lot of configuration options, you should tell us what you have. Also, are you sure that you have bash? Bash and BusyBox is an extremely unusual combination. — Gilles 'SO- stop being evil', Feb 11 '12 at 21:52
GNU bash, version 2.05a.0(1)-release (arm-unknown-linux-gnu) — michelemarcon, Feb 13 '12 at 10:43

score 7 · Accepted Answer · answered Feb 11 '12 at 21:50

You need something that's capable of sending an Ethernet packet that will be seen by the device you want to wake up.

The ether-wake command in BusyBox is exactly what you're after. If your BusyBox doesn't have it, consider recompiling BusyBox to include it.

If you have a sufficiently “bloaty” netcat (BusyBox can have one of two nc implementations, one of which handles TCP only), you can send a manually crafted UDP packet to the broadcast address of the network segment that the device is connected to.

mac=$(printf '\xed\xcb\xa9\x87\x65\x43') # MAC = ed:cb:a9:87:65:43
wol_packet=$(printf "\xff\xff\xff\xff\xff\xff$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac$mac")
echo "$wol_packet" | nc -u 7 192.0.2.255

Another BusyBox utility that you could abuse into sending that packet is syslogd.

syslogd -n -O /dev/null -l 0 -R 192.0.2.255/7 &
syslogd_pid=$!
logger "$wol_packet"
kill $!

If the MAC contains a null byte, you won't be able to craft the packet so easily. Pick a byte that's not \xff and that's not in the MAC, say \x42 (B), and pipe through tr.

echo "$wol_packet" | tr B '\000' | nc -u 7 192.0.2.255

If you really have bash (which is extremely unusual on devices with BusyBox — are you sure you really have bash, and not another shell provided by BusyBox?), it can send UDP packets by redirecting to /dev/udp/$hostname/$port.

echo "$wol_packet" >/dev/udp/192.0.2.255/7

My nc doesn't support -u; syslogd doesn't support -l; finally I don't have /dev/udp devices. :( — michelemarcon, Feb 13 '12 at 10:44
@michelemarcon Your strange device seems to lack the fundamental component of every method I can think of. I recommend compiling and uploading a binary (a more complete BusyBox, for example). — Gilles 'SO- stop being evil', Feb 14 '12 at 06:47

score 1 · Answer 2 · edited Jan 08 '13 at 11:59

1

/dev/udp is recognized by bash and doesn't really exist in the filesystem, so give it a try.

I think you can use syslogd without -l switch, as long as it supports -R.

I have busybox with syslogd withount -R, no nc nor bash and I'm still stuck.

edited Jan 08 '13 at 11:59

mtk

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answered Jan 08 '13 at 10:39

bergonz

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score 0 · Answer 3 · edited Sep 11 '13 at 12:06

0

I have an ssh server running on old HTC dream. My version of busybox also didn't include ether-wake and I'm not skilled enough to compile my own busybox. Fortunately I managed to wake up my PC using:

bash
cat mac2.txt | tr B '\000' >/dev/udp/192.0.1.255/7

Notice that the broadcast ip is different in my network.

I crafted the file (mac2.txt) containing the magic packet on my PC and pushed it to the server via SFTP. Because my mac has null byte I have to use tr to substitute all x42 bytes with 00. It worked like charm.

edited Sep 11 '13 at 12:06

rahmu

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answered Sep 11 '13 at 11:38

zibo

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Why the [Useless Use of Cat](http://partmaps.org/era/unix/award.html#cat)? – rahmu Sep 11 '13 at 12:06

Wake-on-LAN with BusyBox?

3 Answers3