linuxboot

The LinuxBoot project allows you to replace your server's firmware with Linux.

Supported server mainboards

• qemu emulated Q35 systems
• Intel S2600WF
• Dell R630
• Winterfell Open Compute node (works well)
• Monolake Open Compute node (not tested)

Build instructions

You need to provide:

• The vendor UEFI firmware for the mainboard
• A Linux kernel built with the CONFIG_EFI_BDS option enabled
• An initrd.cpio file with enough tools to kexec the rest of the system.

For the initrd, the Heads firmware or u-root systems work well. Both will build minimal runtimes that can fit into the few megabytes of space available.

For everything except qemu, you'll need to copy the vendor ROM dump to boards/$(BOARD)/$(BOARD).rom. Due to copyright restrictions, we can't bundle the ROM images in this tree and you must supply your own ROM from your own machine. qemu can built its own ROM from the edk2 tree, so this is not necessary.

Configure the build system:

cp path/to/s2600wf.rom boards/s2600wf/
make \
	BOARD=s2600wf \
	KERNEL=../path/to/bzImage \
	INITRD=../path/to/initrd.cpio.xz \
	config
make

This will write the values into the .config file so that you don't need to specify them each time. If all goes well you will end up with a file in build/$(BOARD)/linuxboot.rom that can be flashed to your machine. It will take a while since it also clones the LinuxBoot patched version of tianocore/edk2 UDK2018 branch and build it.

Emulating with qemu

If you want to experiment with LinuxBoot you can run it under qemu. No ROM file is necessary, although you still need a Heads or NERF runtime kernel/initrd pair. You can launch the emulator by running:

make run

This will use your current terminal as the serial console, which will likely mess with the settings. After killing qemu by closing the window you will need to run stty sane to restore the terminal settings (echo is likely turned off, so you'll have to type this in the blind).

Adding a new mainboard

Copy Makefile.board from one of the other mainboards and edit it to match your new board's ROM layout. The qemu one is not the best example since it has to match the complex layout of OVMF; most real mainboards are not this messy.

You'll need to figure out which FVs have to be preserved, how much space can be recovered from the ME region, etc. The per-board makefile needs to set the following variables:

• FVS: an ordered list of IFD, firmware volumes and padding
• linuxboot-size: the final size of the ROM image in bytes (we should verify this against the real ROM instead)

More info

• https://www.linuxboot.org/
• https://trmm.net/LinuxBoot_34c3