buildx/docs/reference/buildx_bake.md

buildx bake [OPTIONS] [TARGET...]

Bake is a high-level build command.

Each specified target will run in parallel as part of the build.

Options:

Flag	Description
-f, --file stringArray	Build definition file
--load	Shorthand for --set=*.output=type=docker
--no-cache	Do not use cache when building the image
--print	Print the options without building
--progress string	Set type of progress output (auto, plain, tty). Use plain to show container output (default "auto")
--pull	Always attempt to pull a newer version of the image
--push	Shorthand for --set=*.output=type=registry
--set stringArray	Override target value (eg: targetpattern.key=value)

Description

Bake is a high-level build command. Each specified target will run in parallel as part of the build.

-f, --file FILE

Specifies the bake definition file. The file can be a Docker Compose, JSON or HCL file. If multiple files are specified they are all read and configurations are combined. By default, if no files are specified, the following are parsed:

• docker-compose.yml
• docker-compose.yaml
• docker-bake.json
• docker-bake.override.json
• docker-bake.hcl
• docker-bake.override.hcl

--no-cache

Same as build --no-cache. Do not use cache when building the image.

--print

Prints the resulting options of the targets desired to be built, in a JSON format, without starting a build.

$ docker buildx bake -f docker-bake.hcl --print db
{
   "target": {
      "db": {
         "context": "./",
         "dockerfile": "Dockerfile",
         "tags": [
            "docker.io/tiborvass/db"
         ]
      }
   }
}

--progress

Same as build --progress. Set type of progress output (auto, plain, tty). Use plain to show container output (default "auto").

--pull

Same as build --pull.

--set targetpattern.key[.subkey]=value

Override target configurations from command line. The pattern matching syntax is defined in https://golang.org/pkg/path/#Match.

Example:

docker buildx bake --set target.args.mybuildarg=value
docker buildx bake --set target.platform=linux/arm64
docker buildx bake --set foo*.args.mybuildarg=value # overrides build arg for all targets starting with 'foo'
docker buildx bake --set *.platform=linux/arm64     # overrides platform for all targets
docker buildx bake --set foo*.no-cache              # bypass caching only for targets starting with 'foo'

Complete list of overridable fields: args, cache-from, cache-to, context, dockerfile, labels, no-cache, output, platform, pull, secrets, ssh, tags, target

File definition

In addition to compose files, bake supports a JSON and an equivalent HCL file format for defining build groups and targets.

A target reflects a single docker build invocation with the same options that you would specify for docker build. A group is a grouping of targets.

Multiple files can include the same target and final build options will be determined by merging them together.

In the case of compose files, each service corresponds to a target.

A group can specify its list of targets with the targets option. A target can inherit build options by setting the inherits option to the list of targets or groups to inherit from.

Note: Design of bake command is work in progress, the user experience may change based on feedback.

Example HCL definition:

group "default" {
    targets = ["db", "webapp-dev"]
}

target "webapp-dev" {
    dockerfile = "Dockerfile.webapp"
    tags = ["docker.io/username/webapp"]
}

target "webapp-release" {
    inherits = ["webapp-dev"]
    platforms = ["linux/amd64", "linux/arm64"]
}

target "db" {
    dockerfile = "Dockerfile.db"
    tags = ["docker.io/username/db"]
}

Complete list of valid target fields: args, cache-from, cache-to, context, dockerfile, inherits, labels, no-cache, output, platform, pull, secrets, ssh, tags, target

HCL variables and functions

Similar to how Terraform provides a way to define variables, the HCL file format also supports variable block definitions. These can be used to define variables with values provided by the current environment, or a default value when unset.

Example of using interpolation to tag an image with the git sha:

$ cat <<'EOF' > docker-bake.hcl
variable "TAG" {
    default = "latest"
}

group "default" {
    targets = ["webapp"]
}

target "webapp" {
    tags = ["docker.io/username/webapp:${TAG}"]
}
EOF

$ docker buildx bake --print webapp
{
   "target": {
      "webapp": {
         "context": ".",
         "dockerfile": "Dockerfile",
         "tags": [
            "docker.io/username/webapp:latest"
         ]
      }
   }
}

$ TAG=$(git rev-parse --short HEAD) docker buildx bake --print webapp
{
   "target": {
      "webapp": {
         "context": ".",
         "dockerfile": "Dockerfile",
         "tags": [
            "docker.io/username/webapp:985e9e9"
         ]
      }
   }
}

A set of generally useful functions provided by go-cty are available for use in HCL files. In addition, user defined functions are also supported.

Example of using the add function:

$ cat <<'EOF' > docker-bake.hcl
variable "TAG" {
    default = "latest"
}

group "default" {
    targets = ["webapp"]
}

target "webapp" {
    args = {
        buildno = "${add(123, 1)}"
    }
}
EOF

$ docker buildx bake --print webapp
{
   "target": {
      "webapp": {
         "context": ".",
         "dockerfile": "Dockerfile",
         "args": {
            "buildno": "124"
         }
      }
   }
}

Example of defining an increment function:

$ cat <<'EOF' > docker-bake.hcl
function "increment" {
    params = [number]
    result = number + 1
}

group "default" {
    targets = ["webapp"]
}

target "webapp" {
    args = {
        buildno = "${increment(123)}"
    }
}
EOF

$ docker buildx bake --print webapp
{
   "target": {
      "webapp": {
         "context": ".",
         "dockerfile": "Dockerfile",
         "args": {
            "buildno": "124"
         }
      }
   }
}

Example of only adding tags if a variable is not empty using an notequal function:

$ cat <<'EOF' > docker-bake.hcl
variable "TAG" {default="" }

group "default" {
    targets = [
        "webapp",
    ]
}

target "webapp" {
    context="."
    dockerfile="Dockerfile"
    tags = [
        "my-image:latest",
        notequal("",TAG) ? "my-image:${TAG}": "",
    ]
}
EOF

$ docker buildx bake --print webapp
{
   "target": {
      "webapp": {
         "context": ".",
         "dockerfile": "Dockerfile",
         "tags": [
            "my-image:latest"
         ]
      }
   }
}