OpenBMC cheatsheet

This document is intended to provide a set of recipes for common OpenBMC customisation tasks, without having to know the full yocto build process.

Using a local kernel build

The kernel recipe is in:

 meta-phosphor/common/recipes-kernel/linux/linux-obmc_X.Y.bb

To use a local git tree, change the SRC_URI to a git:// URL without a hostname. For example:

SRC_URI = "git:///home/jk/devel/linux;protocol=git;branch=${KBRANCH}"

The SRCREV variable can be used to set an explicit git commit. The default (${AUTOREV}) will use the latest commit in KBRANCH.

Building for Palmetto

The Palmetto target is palmetto.

If you are starting from scratch without a build/conf directory you can just:

$ cd openbmc
$ TEMPLATECONF=meta-ibm/meta-palmetto/conf . openbmc-env
$ bitbake obmc-phosphor-image

Building for Zaius

The Zaius target is zaius.

If you are starting from scratch without a build/conf directory you can just:

$ cd openbmc
$ TEMPLATECONF=meta-ingrasys/meta-zaius/conf . openbmc-env
$ bitbake obmc-phosphor-image

Building the OpenBMC SDK

Looking for a way to compile your programs for 'ARM' but you happen to be running on a 'PPC' or 'x86' system? You can build the sdk receive a fakeroot environment.

$ bitbake -c populate_sdk obmc-phosphor-image
$ ./tmp/deploy/sdk/openbmc-phosphor-glibc-x86_64-obmc-phosphor-image-armv5e-toolchain-2.1.sh

Follow the prompts. After it has been installed the default to setup your env will be similar to this command

. /opt/openbmc-phosphor/2.1/environment-setup-armv5e-openbmc-linux-gnueabi

Rebuilds & Reconfiguration

You can reconfigure your build by removing the build/conf dir:

rm -rf build/conf

and running openbmc-env again (possibly with TEMPLATECONF set).

Useful D-Bus CLI tools

busctl

http://www.freedesktop.org/software/systemd/man/busctl.html

Great tool to issue D-Bus commands via cli. That way you don't have to wait for the code to hit the path on the system. Great for running commands with QEMU too!

Run as:

busctl call <path> <interface> <object> <method> <parameters>
  • <parameters> example : sssay "t1" "t2" "t3" 2 2 3

Using QEMU

QEMU has a palmetto-bmc machine (as of v2.6.0) which implements the core devices to boot a Linux kernel. OpenBMC also maintains a tree with patches on their way upstream or temporary work-arounds that add to QEMU's capabilities where appropriate.

qemu-system-arm -m 256 -M palmetto-bmc -nographic \
-drive file=<path>/flash-palmetto,format=raw,if=mtd \
-net nic \
-net user,hostfwd=:127.0.0.1:2222-:22,hostfwd=:127.0.0.1:2443-:443,hostname=qemu \

If you get an error you likely need to build QEMU (see the section in this document). If no error and QEMU starts up just change the port when interacting with the BMC...

curl -c cjar -b cjar -k -H "Content-Type: application/json" \
-X POST https://localhost:2443/login -d "{\"data\": [ \"root\", \"0penBmc\" ] }"

or

ssh -p 2222 root@localhost

To quit, type Ctrl-a c to switch to the QEMU monitor, and then quit to exit.

Building QEMU

git clone https://github.com/openbmc/qemu.git
cd qemu
git submodule update --init dtc
mkdir build
cd build
../configure --target-list=arm-softmmu
make

Built file will be located at: arm-softmmu/qemu-system-arm

Use a bridge device

Using a bridge device requires a bit of root access to set it up. The benefit is your qemu session runs in the bridges subnet so no port forwarding is needed. There are packages needed to yourself a virbr0 such as...

apt-get install libvirt libvirt-bin bridge-utils uml-utilities qemu-system-common

qemu-system-arm -m 256 -M palmetto-bmc -nographic \
-drive file=<path>/flash-palmetto,format=raw,if=mtd \
-net nic,macaddr=C0:FF:EE:00:00:02,model=ftgmac100  \
-net bridge,id=net0,helper=/usr/lib/qemu-bridge-helper,br=virbr0

There are some other useful parms like that can redirect the console to another window. This results in having an easily accessible qemu command session. -monitor stdio -serial pty -nodefaults

Booting the host

Login:

curl -c cjar -k -X POST -H "Content-Type: application/json" -d '{"data": [ "root", "0penBmc" ] }' https://${bmc}/login

Connect to host console:

ssh -p 2200 root@bmc

Power on:

curl -c cjar -b cjar -k -H "Content-Type: application/json" -X PUT \
  -d '{"data": "xyz.openbmc_project.State.Host.Transition.On"}' \
  https://${bmc}/xyz/openbmc_project/state/host0/attr/RequestedHostTransition

GDB

SDK build provides GDB and debug symbols:

  • $GDB is available to use once SDK environment is setup
  • Debug symbols are located in .debug/ directory of each executable

To use GDB:

  1. Setup SDK environment;
  2. Run below GDB commands:
    cd <sysroot_of_sdk_build>
$GDB <relative_path_to_exeutable> <path_to_core_file>

Coredump

By default coredump is disabled in OpenBMC. To enable coredump:

echo '/tmp/core_%e.%p' | tee /proc/sys/kernel/core_pattern
ulimit -c unlimited

Cleaning up read-write file system changes

You may want to investigate which file(s) are persisting through the overlay rwfs. To do this, you can list this path and then remove those files which you'd prefer the originals or remove the deletion overlay to restore files.

/run/initramfs/rw/cow/