Build In Docker

Some parts of RIOT's build process can be performed inside a Docker container, which comes with the necessary compilers and toolchains and is fully managed by the build system. It can be enabled by passing BUILD_IN_DOCKER=1 to make.

$ BUILD_IN_DOCKER=1 make

If your user does not have permissions to access the Docker daemon:

$ BUILD_IN_DOCKER=1 DOCKER="sudo docker" make

to always use Docker for building, set BUILD_IN_DOCKER=1 (and if necessary DOCKER="sudo docker") in the environment:

$ export BUILD_IN_DOCKER=1

Targets ran in Docker: DOCKER_MAKECMDGOALS_POSSIBLE

Currently only build related targets are ran in the docker container, the exact list is under DOCKER_MAKECMDGOALS_POSSIBLE variable.

Environment Variables: DOCKER_ENV_VARS

When building in docker one might want for the command ran in docker to inherit variables that might have been set in the command line. e.g.:

BOARD=samr21-xpro USEMODULE=xtimer make -C examples/hello-world

In docker.ink.mk the origin of a variable listed in DOCKER_ENV_VARS is checked and if the origin is environment or command (for make command-line argument) then those variables will be passed to the docker container.

You can also set in DOCKER_ENV_VARS in the environment to add variables to the list, e.g.:

DOCKER_ENV_VARS=BEER_TYPE BEER_TYPE="imperial stout" BUILD_IN_DOCKER=1 make -C examples/hello-world/
docker run --rm -t -u "$(id -u)" \
    ...
    -e 'BEER_TYPE=imperial stout' \
    -w '/data/riotbuild/riotbase/examples/hello-world/' \
    'riot/riotbuild:latest' make

Your application Makefile can also extend DOCKER_ENV_VARS.

Directly Define Environment Variables: DOCKER_ENVIRONMENT_CMDLINE

DOCKER_ENVIRONMENT_CMDLINE can be used to add variables directly to the environment but will need to be prefixed with -e (see option-summary).

e.g.:

DOCKER_ENVIRONMENT_CMDLINE='-e BEER_TYPE="imperial stout"' BUILD_IN_DOCKER=1 make -C examples/hello-world/
docker run --rm -t -u "$(id -u)" \
    ...
    -e 'BEER_TYPE=imperial stout' \
    -w '/data/riotbuild/riotbase/examples/hello-world/' \
    'riot/riotbuild:latest' make

Command Line Variables: DOCKER_OVERRIDE_CMDLINE

Command line arguments are variables that are passed after make e.g. make target FOO=bar, but different to environment variables a variable defined through the command line will take precedence over all assignments of FOO within the makefile (same effect as adding -e for environment variables, see option-summary for more details.

To pass variables overriding the command-line to docker DOCKER_OVERRIDE_CMDLINE may be used:

DOCKER_OVERRIDE_CMDLINE="BEER_TYPE='imperial stout'" BUILD_IN_DOCKER=1 make -C examples/hello-world/ RIOT_CI_BUILD=1
Launching build container using image "riot/riotbuild:latest".
sudo docker run --rm -t -u "$(id -u)" \
    ...
    -w '/data/riotbuild/riotbase/examples/hello-world/' \
    'riot/riotbuild:latest' make  BEER_TYPE='imperial stout' 'RIOT_CI_BUILD=1'

Redefined or Overridden Variables: DOCKER_ENV_VARS_ALWAYS

There is a corner case for the handling of DOCKER_ENV_VARS. If a variable is redefined (+=, =, :=) or overridden then the origin of the variable will be changed to file and there is no way of detecting in Make how it was set.

If this happens after docker.ink.mk this is not an issue, but for all variables susceptible to be defined in the application Makefile this is indeed the case.

A subset of these variables, namely variables relating to dependency resolution are therefore unconditionally passed to docker. The complete list can be found under DOCKER_ENV_VARS_ALWAYS.

CFLAGS

CFLAGS are not automatically passed to docker because they might contain spaces, '"' or other characters that will require escaping. The solution is to pass it with DOCKER_ENVIRONMENT_CMDLINE and escape every character as required.

e.g: if wanting to override STRING_WITH_SPACES

# normal build
CFLAGS=-DSTRING_WITH_SPACES='\"with space\" make
# in docker
DOCKER_ENVIRONMENT_CMDLINE='-e CFLAGS=-DSTRING_WITH_SPACES=\'\\\"with\ space\\\"\'' \
  BUILD_IN_DOCKER=1 make

Alternatively, it is often easier to define the CFLAGS in the Makefile which gets evaluated inside the Docker image again), conditional on a less complex environment variable that gets added to DOCKER_ENV_VARS in the Makefile.