Replicate Travis CI builds on your local machine

When submitting a pull request (PR) to a Travis CI enabled project, an error can occur in the build whose cause is not obvious. While it is possible to debug such an error by committing and pushing to trigger a rebuild, this workflow does not fail-fast. A much better approach is to replicate the build environment Travis uses by obtaining the corresponding Docker image.

To do so, navigate to the Travis CI Job log. Under Worker information, locate the instance name:

Pull the corresponding Docker image:

$ INSTANCE=travisci/ci-sardonyx:packer-1663676759-f9bb8ff4
$ docker pull $INSTANCE

Create the container and attach to it:

$ NAME=travis_$(uuidgen)
$ docker run --name $NAME -dit $INSTANCE /sbin/init
$ docker exec -it $NAME bash -l

Inside the container, assume the role of the travis user:

$ su - travis

You can now execute the commands shown in the Job log (after Build system information) in an environment identical to the one used by Travis CI.