Cobalt Docker builds [ Experimental ]

Cobalt includes minimal [Docker image] definitions for simplifying managing build environments.

The instructions below assume Docker is installed and is able to run basic hello-world verification. docker-compose command is expected to be available as well.

Note: Docker build images are currently provided as experimental, and for reference only.


The simplest usage is:

docker-compose run <platform>

By default, a debug build will be built, with cobalt as a target. You can override this with an environment variable, e.g.

docker-compose run -e CONFIG=devel -e TARGET=nplb <platform>

where config is one of the four optimization levels, debug, devel, qa and gold, and target is the build target passed to ninja

See Cobalt README for full details.

Builds will be available in your ${COBALT_SRC}/out directory.

NB! Note that Docker runs processes as root user by default, hence output files in src/out/<platform> directory have root as file owner.


To parametrize base operating system images used for the build, pass BASE_OS as an argument to docker-compose as follows:

docker-compose build --build-arg BASE_OS="ubuntu:bionic" base

This parameter is defined in docker/linux/base/Dockerfile and is passed to Docker FROM ... statement.

Available parameters for customizing container execution are:

  • BASE_OS: passed to base image at build time to select a Debian-based base os image and version. Defaults to Debian 9. ubuntu:bionic and ubuntu:xenial are other tested examples.
  • PLATFORM: Cobalt build platform, passed to GYP
  • CONFIG: Cobalt build config, passed to GYP. Defaults to debug
  • TARGET: Build target, passed to ninja

The docker-compose.yml contains the currently defined experimental build configurations. Edit or add new service entries as needed, to build custom configurations.


To debug build issues, enter the shell of the corresponding build container by launching the bash shell, i.e.

docker-compose run linux-x64x11 /bin/bash

and try to build cobalt with the usual gyp / ninja flow.