Earthfiles are always named Earthfile, regardless of their location in the codebase.

FROM golang:1.15-alpine3.13
WORKDIR /go-example
​
build:
    COPY main.go .
    RUN go build -o build/go-example main.go
    SAVE ARTIFACT build/go-example /go-example AS LOCAL build/go-example
​
docker:
    COPY +build/go-example .
    ENTRYPOINT ["/go-example/go-example"]
    SAVE IMAGE go-example:latest

package main
​
import "fmt"
​
func main() {
    fmt.Println("hello world")
}

mkdir tutorial
cd tutorial
earthly --artifact github.com/earthly/earthly/examples/tutorial/go:main+part1/part1 ./part1

FROM node:13.10.1-alpine3.11
WORKDIR /js-example
​
build:
    # In JS, there's nothing to build in this simple form.
    # The source is also the artifact used in production.
    COPY src/index.js .
    SAVE ARTIFACT index.js /dist/index.js AS LOCAL ./dist/index.js
​
docker:
    COPY +build/dist dist
    ENTRYPOINT ["node", "./dist/index.js"]
    SAVE IMAGE js-example:latest

console.log("hello world");

mkdir tutorial
cd tutorial
earthly --artifact github.com/earthly/earthly/examples/tutorial/js:main+part1/part1 ./part1

FROM openjdk:8-jdk-alpine
RUN apk add --update --no-cache gradle
WORKDIR /java-example
​
build:
    COPY build.gradle ./
    COPY src src
    RUN gradle build
    RUN gradle install
    SAVE ARTIFACT build/install/java-example/bin /bin AS LOCAL build/bin
    SAVE ARTIFACT build/install/java-example/lib /lib AS LOCAL build/lib
​
docker:
    COPY +build/bin bin
    COPY +build/lib lib
    ENTRYPOINT ["/java-example/bin/java-example"]
    SAVE IMAGE java-example:latest

package hello;
​
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("hello world");
    }
}

apply plugin: 'java'
apply plugin: 'application'
​
mainClassName = 'hello.HelloWorld'
​
jar {
    baseName = 'hello-world'
    version = '0.0.1'
}
​
sourceCompatibility = 1.8
targetCompatibility = 1.8

mkdir tutorial
cd tutorial
earthly --artifact github.com/earthly/earthly/examples/tutorial/java:main+part1/part1 ./part1

FROM python:3
WORKDIR /code
​
build:
     # In Python, there's nothing to build.
    COPY src src
    SAVE ARTIFACT src /src
​
docker:
    COPY +build/src src
    ENTRYPOINT ["python3", "./src/hello.py"]
    SAVE IMAGE python-example:latest

print("hello world")

mkdir tutorial
cd tutorial
earthly --artifact github.com/earthly/earthly/examples/tutorial/python:main+part1/part1 ./part1

You will notice that the recipes look very much like Dockerfiles. This is an intentional design decision. Existing Dockerfiles can be ported to earthfiles by copy-pasting them over and then tweaking them slightly. Compared to Dockerfile syntax, some commands are new (like SAVE ARTIFACT), others have additional semantics (like COPY +target/some-artifact) and other semantics have been removed (like FROM ... AS ... and COPY --from).

You might notice the command COPY +build/... ..., which has an unfamiliar form. This is a special type of COPY, which can be used to pass artifacts from one target to another. In this case, the target build (referenced as +build) produces an artifact, which has been declared with SAVE ARTIFACT, and the target docker copies that artifact in its build environment.

With Earthly you have the ability to pass such artifacts or images between targets within the same Earthfile, but also across different Earthfiles across directories or even across repositories. To read more about this, see the target, artifact and image referencing guide.

Executing the build

In this example, we can see two explicit targets: build and docker. In order to execute the build, we can run, for example:

earthly +docker

The output might look like this:

Notice how to the left of |, within the output, we can see some targets like +base, +build and +docker . Notice how the output is interleaved between +docker and +build. This is because the system executes independent build steps in parallel. The reason this is possible effortlessly is because only very few things are shared between the builds of the recipes and those things are declared and obvious. The rest is completely isolated.

In addition, notice how even though the base is used as part of both build and docker, it is only executed once. This is because the system deduplicates execution, where possible.

Furthermore, the fact that the docker target depends on the build target is visible within the command COPY +build/.... Through this command, the system knows that it also needs to build the target +build, in order to satisfy the dependency on the artifact.

Finally, notice how the output of the build (the docker image and the files) are only written after the build is declared a success. This is due to another isolation principle of Earthly: a build either succeeds completely or it fails altogether.

Once the build has executed, we can run the resulting docker image to try it out:

docker run --rm go-example:latest

docker run --rm js-example:latest

docker run --rm java-example:latest

docker run --rm python-example:latest

Continue tutorial

👉 Part 2: Detailed explanation​