If you’ve never heard of iPXE, it is the official fork of gPXE, which was the ultimate result of the Etherboot Project of old.  Apparently there was a power struggle that caused the primary contributors to leave Etherboot/gPXE and they renamed gPXE to iPXE to distinguish.  Technically gPXE still exists, but for all intents and purposes its a dead project.

If you are completely unfamiliar with both iPXE and gPXE let me summarize.  The industry standard way to network boot is via PXE.  A PXE client is burned into the ROM of your NIC, but because it has to fit in a tight space it is very dumb.  iPXE is an open source PXE client that is modern and very intelligent.  It can execute scripts, it can inspect the system interfaces and SMBIOS, it can download images and scripts via HTTP, FTP, NFS, and more, it has SAN support for booting off of AoE, FCoE, and iSCSI, etc.  It can be used in several ways, including burned into your NIC’s ROM as a replacement (uncommon), booted from USB/ISO/etc media, or most typically it is itself PXE booted such that your dumb PXE client in your NIC boots to iPXE and it then does all the heavy lifting.  If you are doing any type of network booting you should know what iPXE is and if you ever want to do anything fancy, iPXE is the way to do it.  One example many of us like to use is creating an iPXE script which calls out to a web app (PHP commonly) which looks up information from SMBIOS (such as serial number, service tag, MAC address, etc.) and interfaces with a database to make decisions on which image to boot.  You can do lots of fun things.  Most of your next-gen bare metal provisioning tools, such as Razor, rely on iPXE.

There are two really exciting things for me, just added in the last couple months.  The first and most basic is that SmartOS boots natively from iPXE.  In the past, primarily with OpenSolaris, you had to chainload PXEGRUB to boot Solaris, but it looks like some patches were accepted and now you can dump GRUB completely.

The other existing development is the addition of native menus in iPXE.  Historically, if you wanted to create a versatile netboot server you would use iPXE/gPXE to  chainload SYSLINUX’s menu.c32 program which would render your boot selection menu and boot your selected OS.  But no more!  iPXE can do it all on its own now thanks to the addition of 3 commands to iPXE: menu, item, and choose.  With these new commands and liberal use of “goto” labels you can create some extremely complex and powerful setups with no other helper programs in the way.

Lets take a look at a simple menu:

#!gpxe

######## MAIN MENU ###################
:start
menu Welcome to iPXE's Boot Menu
item
item smartos    Boot SmartOS
item 
item shell      Enter iPXE shell
item reboot     Reboot
item
item exit       Exit (boot local disk)
choose --default smartos --timeout 60000 target && goto ${target}

## Utility menu items:
:shell
echo Type exit to get the back to the menu
shell
set menu-timeout 0
goto start

:failed
echo Booting failed, dropping to shell
goto shell

:reboot
reboot

:exit
exit

########## MENU ITEMS #######################
:sdc
kernel /sdc/20121001T165806Z/platform/i86pc/kernel/amd64/unix -B hostname=r720test,standalone=true
initrd /sdc/20121001T165806Z/platform/i86pc/amd64/boot_archive
boot

:smartos
kernel /smartos/20121004T212912Z/platform/i86pc/kernel/amd64/unix
initrd /smartos/20121004T212912Z/platform/i86pc/amd64/boot_archive
boot

You can see here that the “menu” command declares a menu with a title. The elements are items with a label and description (you can assign hot keys as well) and an item with no value is an empty line, and you can use the “–gap –” argument to create section headers, in the form “item –gap — —–SmartOS——-“. Finally, the choose command puts your selection into a named variable and also allows you to specify a default selection and timeout specified in milliseconds. Just about everything else is handled by the “goto” command and labels sprinkled throughout the script. Most importantly, we use the value obtained by the choose command to “goto” the label with the commands to boot the given OS. You can also have multiple menus, one which goes to the other and back, by being creative.

When you couple all this together, you get an iPXE that is more powerful than ever before and extremely exciting.

I’ve taken this opportunity to update the SmartOS Documentation for PXE booting,  using iPXE directly as above is now the officially recommended way to netboot.