A builder is a BuildKit daemon that you can use to run your builds. BuildKit is the build engine that solves the build steps in a Dockerfile to produce a container image or other artifacts.
You can create and manage builders, inspect them, and even connect to builders running remotely. You interact with builders using the Docker CLI.
Docker Engine automatically creates a builder that becomes the default backend for your builds. This builder uses the BuildKit library bundled with the daemon. This builder requires no configuration.
The default builder is directly bound to the Docker daemon and its
context. If you change the
Docker context, your
default builder refers to the new Docker context.
Buildx supports the following build drivers:
docker: uses the BuildKit library bundled into the Docker daemon.
docker-container: creates a dedicated BuildKit container using Docker.
kubernetes: creates BuildKit pods in a Kubernetes cluster.
remote: connects directly to a manually managed BuildKit daemon.
Selected builder refers to the builder that's used by default when you run build commands.
When you run a build, or interact with builders in some way using the CLI,
you can use the optional
--builder flag, or the
to specify a builder by name. If you don't specify a builder,
the selected builder is used.
docker buildx ls command to see the available builder instances.
The asterisk (
*) next to a builder name indicates the selected builder.
$ docker buildx ls
NAME/NODE DRIVER/ENDPOINT STATUS BUILDKIT PLATFORMS
default * docker
default default running v0.11.6 linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/386
my_builder0 default running v0.11.6 linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/386
To switch between builders, use the
docker buildx use <name> command.
After running this command, the builder you specify is automatically selected when you invoke builds.