OpenBMC is an open software framework to build a complete Linux image for a Board Management Controller (BMC).
Clone or download
mikechoifb and facebook-github-bot YAMP REST API handler for sensors will return 0 when device is not ac…
…cessible (instead of N/A)

[YAMP] YAMP's sensor REST API handler will return 0 upon PSU or FAN error (only), instead of "N/A"
Reason: if sensor REST API handler returns "N/A", This will trigger bmc_proxy to use the last known good value (this is a mechanismto deal with intermittent read failure on some platform) Unfortunately, this prevents detector from firing alarm when PSU or FAN is removed. Therefore we need this change.

Test Plan: P60355124

Reviewed By: benwei13

fbshipit-source-id: 04f251ddd
Latest commit e258d56 Nov 9, 2018


OpenBMC is an open software framework to build a complete Linux image for a Board Management Controller (BMC).

OpenBMC uses the Yocto Project as the underlying building and distro generation framework.

Board Status Description
Wedge Build Status A 40G OS-agnostic TOR switch
Yosemite Build Status An open source modular chassis for high-powered microservers
Lightning Build Status A flexible NVMe JBOF
Wedge100 Build Status A 32x100G TOR switch
Backpack LC/FC Build Status Linecard and fabric card in a 128x100G modular open switch
Backpack CMM Build Status Chassis management module in a 128x100G modular open switch
Tioga Pass Build Status A dual-socket compute platform
YosemiteV2 Build Status A refresh of Yosemite
Bryce Canyon Build Status Disk Storage platform


This repository includes 3 set of layers:

  • OpenBMC Common Layer - Common packages and recipes can be used in different types of BMC.
  • BMC System-on-Chip (SoC) Layer - SoC specific drivers and tools. This layer includes the bootloader (u-boot) and the Linux kernel. Both the bootloader and Linux kernel shall include the hardware drivers specific for the SoC.
  • Board Specific Layer - Board specific drivers, configurations, and tools. This layer defines how to configure the image. It also defines what packages to be installed for an OpenBMC image for this board. Any board specific initialization and tools are also included in this layer.

File structure

The Yocto naming pattern is used in this repository. A "meta-layer" is used to name a layer or a category of layers. And recipe-abc is used to name a recipe. The project will exist as a meta layer itself! Within the Yocto Project's distribution call this project meta-openbmc.

The recipes for OpenBMC common layer are found in common.

The BMC SoC layer and board specific layer are grouped together based on the vendor/manufacturer name. For example, all Facebook boards specific code should be in meta-facebook. Likewise, meta-aspeed includes source code for Aspeed SoCs.

How to build

Note: In the instruction set below, references to for some of the steps is an example only and need to be replaced with the respective platform when setting up for a different platform.

  1. Set up the build environment based on the Yocto Project's Quick Start Guide.

  2. Clone the OpenBMC repository and other open source repositories:

$ git clone -b helium
$ cd openbmc
$ ./
  1. Initialize a build directory for the platform to build. In the openbmc directory:
$ source openbmc-init-build-env meta-facebook/meta-wedge

Choose between meta-wedge, meta-wedge100, meta-yosemite, or any of the other platforms listed in the meta-facebook directory. After this step, you will be dropped into a build directory, openbmc/build.

  1. Start the build within the build directory: In general to build for the platform:
$ bitbake <platform>-image

The build process automatically fetches all necessary packages and builds the complete image. The final build results are in openbmc/build/tmp/deploy/images/<platform>. The root password will be 0penBmc, you may change this in the local configuration.

Build Artifacts

  • u-boot.bin - This is the u-boot image for the board.
  • uImage - This the Linux kernel for the board.
  • -image-.cpio.lzma.u-boot - This is the rootfs for the board
  • flash- - This is the complete flash image including u-boot, kernel, and the rootfs.

Kernel & U-Boot Development

By default, OpenBMC build process fetches and build Linux kernel and U-boot directly from GitHub repository.

  • To make local kernel changes and build with the modified kernel:

In the build directory, run

$ devtool modify linux-aspeed


$ devtool modify u-boot

This will create local Linux package under /workspace/sources/linux-aspeed for development

  • To go back to default recipes, run
$ devtool reset linux-aspeed

How can I contribute

If you have an application that can be used by different BMCs, you can contribute your application to the OpenBMC common layer.

If you are a BMC SoC vendor, you can contribute your SoC specific drivers to the BMC SoC layer.

If you are a board vendor, you can contribute your board specific configurations and tools to the Board specific layer. If the board uses a new BMC SoC that is not part of the BMC SoC layer, the SoC specific driver contribution to the BMC SoC layer is also required.