One of the best features of OS X is the built-in ability to clone a customized installation to other machines. By creating a .dmg image of an existing installation in Disk Utility, then using the “Restore” feature to copy it to another disk, you can install a pre-configured OS onto any number of Macintosh workstations.

As much time as this saves, however, you’re still cloning one machine at a time. What if you have tens or even hundreds of machines in your organization? Fortunately, there’s a built-in system to handle that as well. All you have to do is deploy NetInstall.

Creating NetInstall Images:

Ten years ago, when Apple’s administrative tools were aimed more squarely at academia, schools began using NetBoot to deploy their lab machines. By booting workstations off a central server-side system image, machines could run custom configurations that reset cleanly for each user. NetInstall was built on that same technology, allowing your servers to host similar custom images, but install them over the network onto each machine’s local disk.

Creating that image is now done with the System Image Utility, found on OS X Server in the /Applications/Server directory. While an image can be built directly from the OS X installation DVD, they’re hard to customize and seldom up-to-date. You’re better off creating a customized installation on an external drive (or saved as a disk image), then mounting it on your server. While Leopard theoretically allows network installation onto both Intel and PowerPC hardware from the same image, preparing separate images can save time and frustration in the long run.

When you’re ready, launch System Image Utility, and in the “Create an Image” window select “NetInstall Image”. Click “Continue”, then on the next screen enter a name and description of the image you’re preparing. For basic deployment just click “Create”, and save the image in the default location of /Library/NetBoot/NetBootSP0. For more complex configurations, click “Customize” to add post-install scripts, filtering by hardware type, or allow more client-side installation options.

You may want to go take lunch while your image builds, but when it’s done you can repeat the process for each image you’ll need to deploy over your network.

Configuring The NetBoot Service:

Once your images are prepared, the next step is to configure NetInstall on your network. Launch Server Admin and select the NetBoot service from the left column. Click the “Settings” icon in the toolbar, then choose the “General” pane. Here you’ll choose the network interface for NetInstall to run on (typically Ethernet 1), and the volume to store images and client data (the system array, in this example, though you may prefer another volume if you’re mixing NetBoot and NetInstall).

Now move to the “Images” pane. Check “default” if you’ve got a single image, or there’s an image you’d like to force if one isn’t specified. Next check “enable” for each of the images you’re planning to deploy, and choose the protocol over which you’ll offer them.

The NetBoot service can run over either HTTP or NFS. Given that most companies filter HTTP traffic, or engage some kind of web proxy for port 80, utilizing NFS is usually the better choice. In these circumstances, be sure to allow traffic over port 1049 on your internal network.

With these options set, click “Save”, then click “Start NetBoot” to take the service live.

Configuring Clients For NetInstall:

Once NetInstall is running happily on your network, all that’s left is to boot your client machines. If you’re only offering one image (and you’ve marked it as the “default” in the “Images” pane), you can simply restart your machines while holding down the “n” key. If you’re offering multiple NetInstall images, open System Preferences on your client machines, and choose the appropriate image to install from the “Startup Disk” pane. When you restart, the computer will boot into the installer automatically. You’ll need each computer connected to the network during this procedure, and you’ll save yourself a world of trouble if they’re using ethernet rather than wireless.

That’s all there is to it. Allowing you to save hours, if not days, of work on every rollout, NetInstall is one of the most powerful, and easiest, tricks up the Macintosh administrator’s sleeve.

Recommended Reading: There’s no better, or more extensive, explanation of BSDP (the protocol on which NetInstall is built) than the amazing How NetBoot Works by the even more amazing Mike Bombich.