Skip to content
Go to file

Latest commit

* u-bmc.go: Fix Change in DefaultRamfs

Signed-off-by: Christian Walter <>

* Fix integration Test

Signed-off-by: Christian Walter <>

Git stats


Failed to load latest commit information.
Latest commit message
Commit time


Build Status Go Report Card License


u-bmc uses u-root to create a Linux OS distribution that is fully open-source.

u-bmc borrows and contributes to OpenBMC which has similar high-level goals. The main difference is that u-bmc chooses to challenge the industry status quo. E.g. where OpenBMC uses IPMI, u-bmc uses gRPC.




BMC software has historically been known to be insecure. There is no inherent reason for that. u-bmc sets out to improve this by offering an alternative built on modern technologies.


u-bmc is still in experimental stage and is currently only supporting BMCs based on ASPEED AST2400. Other BMC SOCs are planned, and if you want to contribute let us know.

Currently the supported boards are:

  • Open Compute Project: Quanta F06 Leopard DDR3
  • Aspeed AST2500 Evaluation Board

Planned boards are:

  • Nuvoton Poleg BMC NPCM7XX Evaluation Board
  • Open Compute Project: Quanta F20 Yosemite
  • Tyan Tempest CX S7106

Do you want to become a contributor of a board? Let us know!


To give you some sense of what we want to create:

  • All function exported over gRPC like:
    • Serial-over-LAN
    • Sensor data
    • iKVM
    • Updating BIOS
    • POST information
  • Implementation of OpenMetrics for Prometheus integration for sensors
  • Offer SSH server for on-platform debugging
    • Support SSH CA-signed certificates to avoid having to upload a bunch of certs
  • USB device emulation
    • Must have: USB storage from image
    • Cool to have: USB ethernet to host, replaces KCS IPMI interface.
    • Cool to have: USB graphics card + mouse + keyboard for KVM



sudo apt install gcc-arm-none-eabi mtd-utils golang-1.12 fakeroot flex bison device-tree-compiler bc libssl-dev libelf-dev qemu-kvm

Clone source code:

go get
cd ~/go/src/

Setup configuration:

# SSH ECDSA public keys does not work for now
cp ~/.ssh/
# Agree to the terms of the configured ACME server
# By default it's just a toy ACME server so this is fine, but if you're
# using another ACME server like Let's Encrypt (LE) ensure you agree to their terms.
# For LE, you can find them at
touch config/i_agree_to_the_acme_terms
go generate ./config/

Builld image:

make get

Since u-bmc uses signed binaries it is important that you back up the contents of boot/keys/ after building as u-bmc will only accept updates signed with these keys.


To run the simulator and the integration test you need a special Qemu from Using the upstream Qemu will not work predictably.


Trying out u-bmc is easiest using the simulator. To launch it, run:

# Launch a local ACME server
make pebble &
# Launch u-bmc simulator
make sim
# (Optional, run in another terminal) Launch a local emulated BIOS to produce some data on the UART
# Needs to have u-bmc simulator above running for it to attach correctly.
make run-ovmf

When simulating the following TCP/IP ports are set up:

  • 6053/udp: u-bmc DNS
  • 6443/tcp: u-bmc gRPC
  • 9370/tcp: u-bmc OpenMetrics

When the u-bmc guest tries to access a local service called ubmc-pebble is started which uses Let's Encrypt's pebble service to generate an HTTPS certificate. The CA used is located in config/sim-ca.crt.

You can interact with u-bmc running in the simulator by using ubmcctl:

go install
# The root CA is regenerated every time pebble is started to prevent
# testing to accidentally become production
curl https://localhost:14000/root --cacert config/sim-pebble.crt > root.crt
echo '' | sudo tee -a /etc/hosts
SSL_CERT_FILE=root.crt ubmcctl -host

If you restart pebble you need to update root.crt.


The easiest way to run all unit tests is to run make test.

To run the integration tests:

make integration/bzImage
export UBMC_QEMU=qemu-system-arm
cd integration
go test

If you're using a supported platform and want to try it on your hardware you can use socflash_x64 provided by ASPEED like this:

echo This is extremely likely to break things as u-bmc is still experimental
sudo ./socflash_x64 of=bmc-backup.img if=flash.img lpcport=0x2e option=glc

Uploading a new version

If you want to quickly upload a new build of u-bmc without updating the kernel, you can use SCP like this:

scp root/bbin/bb my-ubmc:/bb
scp root/bbin/bb.sig my-ubmc:/bb.sig
ssh my-ubmc
# Verify that bb is sane by executing /bb
# Should return:
# <timestmap> You need to specify which command to invoke.
# Exception: /bbin/bb exited with 1
# [tty], line 1: /bbin/bb
mv /bb /bbin/bb
mv /bb.sig /bbin/bb.sig
# Verify the signature before rebooting
gpgv /etc/ /bbin/bb.sig /bbin/bb
shutdown -r



Since this is an early experiment if this is at all interesting for you or your company, do reach out in our Slack channel:

You can’t perform that action at this time.