Rolling out new Linux installations over the network and reimaging old ones is easy, once you have the necessary servers in place and have your clients set up to network-boot. It's a bit complicated on x86 hardware because the x86 platform was not originally designed for network booting, so even now, network booting x86 clients is rather hit-or-miss. Of course, Linux gives you a number of boot options, so you can make it work one way or another:
Debian and Fedora Linux provide network-booting images for CD-ROM and USB devices. They also support Preboot Execution Environment (PXE) booting, which means you don't need a CD-ROM or USB drive—all you need is a network interface and a PC BIOS that support PXE booting, and a PXE boot server.
If your BIOS or NIC do not support PXE booting, then go to the Etherboot project site (http://www.etherboot.org). Download a boot image, copy it to a floppy disk, configure the system to boot from the diskette, and you're good to go.
If you're putting together a network with older gear, it might not support PXE boot; however, you might be able to to upgrade it without too much hassle. The first thing to check is the BIOS. Anything older than 2000 or so probably won't support PXE booting, but you might be able to flash-upgrade the BIOS and get support for PXE booting and other modern features.
Once the BIOS is squared away, check your network interface. Some network cards support PXE boot out of the box; this is the best and easiest way. Some have an empty socket designed to hold an add-on boot ROM chip.
Some just plain won't support PXE booting at all. You can purchase programmed ROM chips for around $18. You can also buy blank ROMs to put your own boot code on, which seems like a lot of work, but if that's what you want to do, then the Etherboot project (http://www.etherboot.org) will help you.
Or, again, avoid all this, and use an Etherboot diskette.
Booting from a USB drive, whether it's a large hard drive or a little USB pen drive, is also hit-or-miss. Newer machines should support it, though there are a few gotchas to look out for. Your USB drive must be plugged in before you power up the machine. Then, check your BIOS settings to make sure that all possible USB support options are enabled.
Next, check to see if it has a "boot to an alternate device" option; for example, on a newer Phoenix BIOS, you press F11 to get an alternate boot device menu. This saves the hassle of setting the boot order in the BIOS settings.
If there is not a specific "boot to USB flash drive" setting, try all available USB devices, such as USB-Zip or USB-HDD.
Once a client system is booted and on the network, the rest of the installation proceeds just as if you were using ordinary installation CDs or DVDs. Even better, you can set up customized automated installations so that once the installer is booted, and the client is connected to the installation server, you don't have to lift a finger.