[bdcravens]

Kind of odd to see the homepage show Vagrant as the install mechanism, even though it supports Docker as well. In 2017, I'd think more developers are likely to run Docker than Vagrant workloads on their machine.

[fenollp]

Probably easier to run Docker inside Vagrant than Docker inside Docker.

[EngineerBetter]

Concourse doesn't run Docker, it uses something called Garden to run OCI containers from Docker images.

Those containers can run the Docker daemon though, if you like.

[krakensden]

The version of Garden it uses basically just shells out to Docker. Run 'top' on a busy Concourse worker, it's fun.

[wlamartin]

Garden makes use of runc (an Open Container Initiative project with a lot of contributions from Docker), in the same way containerd (component included in Docker) makes use of runc to run images. You won't find the docker engine being used by Garden.

Edit: I _think_ what you're likely seeing (if you are seeing docker in the top output) is Concourse using the docker-image-resource to pull images for your tasks to a local docker registry.

[scaryclam]

I still see the majority of developers that I've met using Vagrant. I gave my own team the option of both and as yet, I'm the only one using docker, so I think you'd be surprised. Docker seems to have gone out of favour in a lot of places.

[arwineap]

Concourse makes use of a feature of the kernel that is not compiled in on all distros.

Archlinux for example does not compile in user namespaces. Vagrant is the most cross-platform option for quick local concourse testing.