Shell Scripting: Expert Recipes for Linux, Bash, and More

Recipe 19-2: PXE Booting

It used to be that a server would be installed by booting from a tape, floppy, CD, or DVD, and the operator would answer a set of questions in order to get the operating system installed as required. This still happens today, but large organizations do not have the time to do this low-level repetitive task for each of the thousands of servers they have installed. Small organizations also benefit from the fast, automated, and identical installs that this method provides. Automated, hands-off network installs are required for this, and DHCP and PXE are pretty much the only way to do this on x86 architecture. RedHat’s Kickstart system is the most widely used automated installation infrastructure for Linux, and this recipe provides the most basic bare-bones setup to perform network installations.

This is not a systems administration book, so setting up DHCP, TFTP, and NFS servers is not covered here. This should provide a reasonable starting point for those topics, but its real purpose is to show how numbers such as IP addresses can be manipulated in shell scripts, even without apparently doing any math. The printf command can do a lot of conversion on-the-fly.

Technologies Used

• PXE
• Kickstart
• printf

Concepts

When a machine uses the PXE (Pre-eXecution Environment) to boot directly off the network, it needs to get an IP address from a DHCP server. The DHCP server can also give it the details of a TFTP server from which to retrieve an executable file. Typically ...