Building multiple Docker images that share common dependencies? Need to build all your services at once? depot bake lets you build multiple images in parallel from a single file, dramatically speeding up your builds while taking advantage of shared work between images.
Traditional approaches to building multiple images often involve sequential builds using tools like make or shell scripts. This means waiting for each image to complete before starting the next one, and rebuilding shared dependencies multiple times.
With depot bake, you can:
By default, depot bake looks for these files in your project root:
compose.yaml, compose.yml, docker-compose.yml, docker-compose.yamldocker-bake.json, docker-bake.override.jsondocker-bake.hcl, docker-bake.override.hclRun bake with no arguments to build the default group or all services:
depot bakeUse the -f flag to specify a custom bake file:
depot bake -f my-bake-file.hclBuild only specific targets instead of all:
depot bake app dbHCL is the recommended format for bake files as it provides the most features and flexibility.
group "default" {
targets = ["app", "db", "cron"]
}
target "app" {
dockerfile = "Dockerfile.app"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/app:latest"]
}
target "db" {
dockerfile = "Dockerfile.db"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/db:latest"]
}
target "cron" {
dockerfile = "Dockerfile.cron"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/cron:latest"]
}You can think of each target as a Docker build command, where you specify the Dockerfile, platforms, and tags for the image. These targets can be grouped together in a group to build them all at once.
Our optimized instances of BuildKit will build these images in parallel, automatically deduplicating work across targets.
Make your bake files more flexible with variables:
variable "TAG" {
default = "latest"
}
variable "REGISTRY" {
default = "myrepo"
}
target "app" {
dockerfile = "Dockerfile.app"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["${REGISTRY}/app:${TAG}"]
}Override variables from the command line:
TAG=v1.0.0 REGISTRY=mycompany depot bakeUse contexts to specify dependencies between targets in a bake file. A common use of this is to highlight that targets share a base image, so you can deduplicate work by only building that base image once:
target "base" {
dockerfile = "Dockerfile.base"
platforms = ["linux/amd64", "linux/arm64"]
}
target "app" {
contexts = {
base = "target:base"
}
dockerfile = "Dockerfile.app"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/app:latest"]
}
target "worker" {
contexts = {
base = "target:base"
}
dockerfile = "Dockerfile.worker"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/worker:latest"]
}In your Dockerfiles, reference the base context:
# Dockerfile.app
FROM base
# ... rest of your app DockerfileYou can use the matrix key to parameterize a single target to build images for different inputs. This can be helpful if you have a lot of similarities between targets in your bake file.
target "service" {
name = "service-${item}"
matrix = {
item = ["frontend", "backend", "api"]
}
dockerfile = "Dockerfile.${item}"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/${item}:latest"]
}Note: The name property is required when using the matrix property to create the unique image build for each value in the matrix.
You can use your existing Docker Compose files as a bake file. There are limitations compared to HCL, like not supporting inherits or variable blocks. But it's a great way to build all of your services in parallel without needing to rewrite your existing Compose files.
services:
app:
build:
dockerfile: Dockerfile.app
platforms:
- linux/amd64
- linux/arm64
image: myrepo/app:latest
db:
build:
dockerfile: Dockerfile.db
platforms:
- linux/amd64
- linux/arm64
image: myrepo/db:latest
worker:
build:
dockerfile: Dockerfile.worker
platforms:
- linux/amd64
- linux/arm64
image: myrepo/worker:latestBuild all services defined in the Docker Compose file with:
depot bake -f docker-compose.ymlIn some cases you may want to shard your container builds out across different Depot projects so you can have the full BuildKit host dedicated to the build. For compose, you can specify different Depot projects per service.
services:
frontend:
build:
dockerfile: ./Dockerfile.frontend
x-depot:
project-id: project-id-1
backend:
build:
dockerfile: ./Dockerfile.backend
x-depot:
project-id: project-id-2You can also specify the project ID in HCL for each target:
target "app" {
dockerfile = "Dockerfile.app"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/app:latest"]
project_id = "project-id-1"
}
target "db" {
dockerfile = "Dockerfile.db"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/db:latest"]
project_id = "project-id-2"
}
target "worker" {
dockerfile = "Dockerfile.worker"
platforms = ["linux/amd64", "linux/arm64"]
tags = ["myrepo/worker:latest"]
project_id = "project-id-3"
}Load specific targets to your local Docker daemon by including the target name after the load flag:
depot bake --load appThis only loads the specified target, not all targets in the bake file.
You can save built images to the Depot Registry for later use:
depot bake --save --metadata-file=build.jsonIf you want to specify a specific tag for the images being stored in the registry, you can do so by using the --save-tag flag:
depot bake --save --save-tag myrepo/app:v1.0.0You can pull specific targets out of the Depot Registry later using the depot pull command:
depot pull --project <project-id> --target app,db <build-id>Or push to your registry after tests pass:
depot push --project <project-id> --target app \
--tag myregistry/app:v1.0.0 <build-id>--build-arg) to a targetYou can pass build arguments to your targets in the bake file using the args block. This is useful for passing environment variables or other configuration options to your Docker builds.
target "app" {
args = {
NODE_VERSION = "18"
ENV = "production"
}
}You can use the depot/bake-action in your GitHub Actions workflows to leverage depot bake for building your bake files with our Docker build service:
name: Build images
on: push
jobs:
bake:
runs-on: ubuntu-latest
permissions:
id-token: write
contents: read
steps:
- uses: actions/checkout@v4
- uses: depot/setup-action@v1
- uses: depot/bake-action@v1
with:
file: docker-bake.hcl
push: trueinherits to reduce duplicationdepot/bake-action