Lojic Technologies Blog » sysadmin

Ubuntu Linux 8.04 – Wake on LAN

Brian Adkins — Wed, 03 Sep 2008 05:23:57 +0000

Now that I’ve switched to a Macbook Pro with OSX Leopard as my primary desktop, I’ve located my Ubuntu machine in another part of the house to be accessible to my children. Not wanting to walk to the room where it’s located just to flip the power switch, I researched how to get “wake on LAN” working, so I could power it up remotely.

1. Enable the appropriate setting in your BIOS. Mine had something to do with wake on PCI device.

2. Install ethtool if you don’t already have it.

sudo apt-get install ethtool
cd /etc/init.d
sudo vim wakeonlanconfig

Add the following lines to that file:

#!/bin/bash
ethtool -s eth0 wol g

Install the script:

sudo update-rc.d -f wakeonlanconfig defaults

Run the script:

sudo /etc/init.d/wakeonlanconfig

3. Keep the network interface alive after shut down.

sudo vim /etc/init.d/halt

Change the following line:

halt -d -f -i $poweroff $hddown

to the following line (i.e. remove the -i)

halt -d -f $poweroff $hddown

4. Get the MAC address

ifconfig | grep HW

5. Send the magic packet via the following Ruby program:

require 'socket'
mac_addr = "x21x53x39xB3x90x42"
s = UDPSocket.new
s.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, 1)
s.send("xff"*6 + mac_addr*16, Socket::SO_BROADCAST, '10.0.0.255', 7)

Use vimdiff to display subversion diffs

Brian Adkins — Tue, 27 Nov 2007 15:14:38 +0000

I prefer using vimdiff or gvimdiff to view differences between files. When researching ways to allow using vimdiff to view subversion differences, I came across this article.

The bottom line is that subversion passes the two relevant arguments as the 6th and 7th arguments, so the following shell script wrapper does the trick:
#!/bin/sh /usr/bin/gvimdiff ${6} ${7}

Save the script as gvimdiff_wrapper.sh, make it executable and accessible on your path. Then modify $HOME/.subversion/config to have the following line:
diff-cmd = gvimdiff_wrapper.sh

That will allow you to use gvimdiff to display the diff generated by svn diff my_file.txt

Web Hosting Bandwidth Constant

Brian Adkins — Mon, 03 Sep 2007 06:42:12 +0000

365.25 days per year
12 months per year
24 hours per day
60 minutes per hour
60 seconds per minute
1,024 MB per GB
1,024 KB per MB
8 kilobits (kb) per kilobyte (KB)

Put that all together and you get the following:

3.19 (month kb) / (sec GB)

So when you see a web hosting company stating a bandwidth per month (in GB), you can multiply that by 3.19 to get a kilobits per second figure. In other words, 18 GB/month of bandwidth is the amount of bandwidth that a 56Kb modem would consume at full capacity, and 480 GB/month is roughly the same as a 1.5Mb T1 line.

Etch is here

Brian Adkins — Mon, 09 Apr 2007 04:36:21 +0000

Wow, debian.org has finally released version 4.0 (”etch”). debian is an awesome linux distribution for servers, but 3.1 has some rather old packages. In particular, I need Apache 2.2 for mod_proxy_balancer, so I installed Ubuntu 6.10 server on my last server to get more recent packages. I expect to use debian 4.0 for future server installs.

I found out about this from distrowatch.com and there’s a blurb on slashdot.org about it.