The wiki is being retired!
Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!
coreboot in itself is "only" minimal code for initializing a mainboard with peripherals. After the initialization, it jumps to a payload.
GRUB2 is the standard bootloader for Linux and other Unix-like operating systems.
You can use GRUB2 as a coreboot payload, too, in order to boot and operating system from a hard drive, for instance.
FILO is a simple bootloader with filesystem support.
It will be deprecated in favor of GRUB2 soon.
Etherboot is a network bootloader. It provides a direct replacement for proprietary PXE ROMs, with many extra features such as DNS, HTTP, iSCSI, etc.
Older versions of Etherboot included parts of FILO, and thus supported SATA and USB booting.
The new GPXE is not yet supported, various code changes are required before it can work with coreboot.
Mitch Bradley's Open Firmware, an IEEE1275-1994 Open Firmware implementation, can also be used as coreboot payload.
OpenBIOS — IEEE1275-1994 Open Firmware.
Coreboot can use a Linux kernel as payload directly. That is, the kernel is included in the ROM chip where coreboot resides.
Alternatively, you can also boot a Linux kernel from your hard drive using either the FILO or GRUB2 payloads, of course.
FreeBSD can be booted via coreboot with the help of ADLO.
OpenBSD can also be booted via coreboot with the help of ADLO.
This use-case is not well-tested yet, though.
NetBSD/x86 boot code is known to work with LegacyBIOS.
jakllsch has worked on a partially-complete port of the x86 boot code to the role of native payload. However, with the advent of LegacyBIOS, this is likely to become less of a priority. Consult Coreboot and NetBSD for further information.
Windows can be booted with the help of ADLO.
This use-case is not well-tested yet, though.
OpenSolaris has multiboot compliant kernels, and so it is possible to boot it with GRUB2 (pending some bug fixes). Some Sun engineers even worked on it, see http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6475349 for information.
Currently, GRUB2 refuses to load the kernel due to a small bug in the multiboot header of the kernel, but the kernel still refuses to work if that is worked around. Maybe they reintroduced some BIOS calls again?
See also this blog entry.
Memtest86 / Memtest86+
Memtest86 is a program which checks your RAM modules.
It can be run from within GRUB, but also as a coreboot payload (i.e. included in your ROM chip).
ADLO — Glue layer to 16-bit Bochs BIOS. Allows booting Windows and OpenBSD.
LegacyBIOS is an open-source implementation of a legacy BIOS which can also be used as coreboot payload.
Libpayload is a helper-library for payload-writers.
coreinfo is a coreboot payload which can display various system information.
Bayou is the working name for a coreboot payload that can choose, load and run other payloads from a LAR archive on the ROM.
GRUB invaders multi-boot compliant space invaders game.
It can either be started from within GRUB (as a "kernel"), or it can be used as a coreboot payload.
tint is a falling blocks game.
Possible future payloads
The following payloads might or might not work (with more or less changes required) with coreboot — their usage hasn't been tested or documented so far.
- CodeGen's SmartFirmware — IEEE1275-1994 Open Firmware
- GNUFI (UEFI)
- Plan 9 — A distributed operating system.
- RedBoot / eCos — Real-time OS for embedded systems; initial port to ELF completed but no longer available.
- GPXE — Needs some code changes
- OpenSolaris / BeleniX
- Windows CE
- NanoVM (small JVM)
- uip / lwip (small TCP/IP stacks)
The payload was originally intended to be a Linux kernel stored in flash. Flash ROM growth rate was anticipated optimistically however, today there are not many mainboards that actually have enough flash ROM room for a kernel. 512KB can be seen here-and-there and a few boards come with 1MB. Recent kernels really want that MB, and then you'll only have room for 300-400 KB of initial ramdisk, which could be too small too, depending on the application. During testing, a payload may also be downloaded via X-Modem from the serial debug console, saving flashing time.
So, other payloads are used; the two major ones are FILO (soon to be deprecated in favor of GRUB2) and Etherboot (soon to be deprecated in favor of GPXE). FILO loads a kernel from a filesystem on an IDE device and Etherboot loads a kernel from the network or from a filesystem on an IDE device.
If you're using FILO there is no Linux kernel until FILO loads it, and the kernel loaded by FILO (or Etherboot) can absolutely be the one you want to run in your system. Just set it up with the correct root and init commandline so that it can start init.