Get useful system stats

The name of you Mac is displayed in the login window below the words "Mac OS X". Since Mac OS X 10.6.1, you can click on the name of your Mac to show different statistics about your machine. Each time you click, it will cycle through different bits of information that are particularly useful when troubleshooting problems.

The order of the statistics are as follows:

One click: Your OS X version number (e.g. Version 10.6.1)
Two clicks: Your OS X build number (e.g. Build 94KM1)
Three clicks: Your mac's serial number (e.g. 47HY74G9LNG)
Four clicks: Your mac's IP address (e.g. 196.254.0.1)
Five clicks: The status of any networked account
Six clicks: The date and time (e.g. Saturday, OCTOMBER 24 2009 4:02:31 AM GMT)
Seven clicks: Back to where you started, the name of your computer.

So you click a few times and set the information line to your favourite thing, but next time you log in, it has changed back to the name of your mac. To change the bit of information that appears first, you need to do a bit of tinkering in the Terminal (Applications/Utilities). Open Terminal and type the following command:

sudo defaults write /Library/Preferences/com.apple.loginwindow AdminHostInfo HostName

Depending on which piece of information you want displayed, replace HostName with one of the following:

SystemVersion
SystemBuild
SerialNumber
IPAddress
DSStatus
Time

After doing this, hit return, and the next time you view your login window the information you chose will be displayed. To change it back to normal, simply repeat the command with HostName at the end.

Change the background image of Login Window

There are ways to change the background image by replacing the Aqua Blue image, but that is slightly crude. A better way to do it is using the Terminal. Type the following command and press return:

sudo defaults write /Library/Preferences/com.apple.loginwindow DesktopPicture /Users/Shared/mynewbackground.jpg


The last part, /Users/Shared/mynewbackground.jpg is the location of the image you want to use. You don't have to type it out. Just paste the command as far as DesktopPicture and put a space after it. Then find your image in the Finder, and drag it onto the Terminal window. The address to your image should just appear. As far as I can tell, you have to place the image in a place that all users have access to (the shared folder is a good place).

To change back to the normal Aqua Blue image, type the following command and press return:

sudo defaults write /Library/Preferences/com.apple.loginwindow DesktopPicture /Library/Desktop\ Pictures/Aqua\ Blue.jpg