Examples using the Docker Engine SDKs and Docker API

Estimated reading time: 22 minutes

After you install Docker, you can install the Go and Python SDKs and also try out the Docker Engine API.

Each of these examples show how to perform a given Docker operation using the Go and Python SDKs and the HTTP API using curl.

Run a container

This first example shows how to run a container using the Docker API. On the command line, you would use the docker run command, but this is just as easy to do from your own apps too.

This is the equivalent of typing docker run alpine echo hello world at the command prompt:

package main

import (
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/api/types/container"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	reader, err := cli.ImagePull(ctx, "docker.io/library/alpine", types.ImagePullOptions{})
	if err != nil {
		panic(err)
	}
	io.Copy(os.Stdout, reader)

	resp, err := cli.ContainerCreate(ctx, &container.Config{
		Image: "alpine",
		Cmd:   []string{"echo", "hello world"},
		Tty:   true,
	}, nil, nil, "")
	if err != nil {
		panic(err)
	}

	if err := cli.ContainerStart(ctx, resp.ID, types.ContainerStartOptions{}); err != nil {
		panic(err)
	}

	statusCh, errCh := cli.ContainerWait(ctx, resp.ID, container.WaitConditionNotRunning)
	select {
	case err := <-errCh:
		if err != nil {
			panic(err)
		}
	case <-statusCh:
	}

	out, err := cli.ContainerLogs(ctx, resp.ID, types.ContainerLogsOptions{ShowStdout: true})
	if err != nil {
		panic(err)
	}

	io.Copy(os.Stdout, out)
}

import docker
client = docker.from_env()
print client.containers.run("alpine", ["echo", "hello", "world"])

$ curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
  -d '{"Image": "alpine", "Cmd": ["echo", "hello world"]}' \
  -X POST http:/v1.24/containers/create
{"Id":"1c6594faf5","Warnings":null}

$ curl --unix-socket /var/run/docker.sock -X POST http:/v1.24/containers/1c6594faf5/start

$ curl --unix-socket /var/run/docker.sock -X POST http:/v1.24/containers/1c6594faf5/wait
{"StatusCode":0}

$ curl --unix-socket /var/run/docker.sock "http:/v1.24/containers/1c6594faf5/logs?stdout=1"
hello world

Run a container in the background

You can also run containers in the background, the equivalent of typing docker run -d bfirsh/reticulate-splines:

package main

import (
	"fmt"
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/api/types/container"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	imageName := "bfirsh/reticulate-splines"

	out, err := cli.ImagePull(ctx, imageName, types.ImagePullOptions{})
	if err != nil {
		panic(err)
	}
	io.Copy(os.Stdout, out)

	resp, err := cli.ContainerCreate(ctx, &container.Config{
		Image: imageName,
	}, nil, nil, "")
	if err != nil {
		panic(err)
	}

	if err := cli.ContainerStart(ctx, resp.ID, types.ContainerStartOptions{}); err != nil {
		panic(err)
	}

	fmt.Println(resp.ID)
}

import docker
client = docker.from_env()
container = client.containers.run("bfirsh/reticulate-splines", detach=True)
print container.id

$ curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
  -d '{"Image": "bfirsh/reticulate-splines"}' \
  -X POST http:/v1.24/containers/create
{"Id":"1c6594faf5","Warnings":null}

$ curl --unix-socket /var/run/docker.sock -X POST http:/v1.24/containers/1c6594faf5/start

List and manage containers

You can use the API to list containers that are running, just like using docker ps:

package main

import (
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	containers, err := cli.ContainerList(context.Background(), types.ContainerListOptions{})
	if err != nil {
		panic(err)
	}

	for _, container := range containers {
		fmt.Println(container.ID)
	}
}

import docker
client = docker.from_env()
for container in client.containers.list():
  print container.id

$ curl --unix-socket /var/run/docker.sock http:/v1.24/containers/json
[{
  "Id":"ae63e8b89a26f01f6b4b2c9a7817c31a1b6196acf560f66586fbc8809ffcd772",
  "Names":["/tender_wing"],
  "Image":"bfirsh/reticulate-splines",
  ...
}]

Stop all running containers

Now that you know what containers exist, you can perform operations on them. This example stops all running containers.

Note: Don’t run this on a production server. Also, if you are using swarm services, the containers stop, but Docker creates new ones to keep the service running in its configured state.

package main

import (
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	containers, err := cli.ContainerList(ctx, types.ContainerListOptions{})
	if err != nil {
		panic(err)
	}

	for _, container := range containers {
		fmt.Print("Stopping container ", container.ID[:10], "... ")
		if err := cli.ContainerStop(ctx, container.ID, nil); err != nil {
			panic(err)
		}
		fmt.Println("Success")
	}
}

import docker
client = docker.from_env()
for container in client.containers.list():
  container.stop()

$ curl --unix-socket /var/run/docker.sock http:/v1.24/containers/json
[{
  "Id":"ae63e8b89a26f01f6b4b2c9a7817c31a1b6196acf560f66586fbc8809ffcd772",
  "Names":["/tender_wing"],
  "Image":"bfirsh/reticulate-splines",
  ...
}]

$ curl --unix-socket /var/run/docker.sock \
  -X POST http:/v1.24/containers/ae63e8b89a26/stop

You can also perform actions on individual containers. This example prints the logs of a container given its ID. You need to modify the code before running it to change the hard-coded ID of the container to print the logs for.

package main

import (
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	options := types.ContainerLogsOptions{ShowStdout: true}
	// Replace this ID with a container that really exists
	out, err := cli.ContainerLogs(ctx, "f1064a8a4c82", options)
	if err != nil {
		panic(err)
	}

	io.Copy(os.Stdout, out)
}

import docker
client = docker.from_env()
container = client.containers.get('f1064a8a4c82')
print container.logs()

$ curl --unix-socket /var/run/docker.sock "http:/v1.24/containers/ca5f55cdb/logs?stdout=1"
Reticulating spline 1...
Reticulating spline 2...
Reticulating spline 3...
Reticulating spline 4...
Reticulating spline 5...

List all images

List the images on your Engine, similar to docker image ls:

package main

import (
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	images, err := cli.ImageList(context.Background(), types.ImageListOptions{})
	if err != nil {
		panic(err)
	}

	for _, image := range images {
		fmt.Println(image.ID)
	}
}

import docker
client = docker.from_env()
for image in client.images.list():
  print image.id

$ curl --unix-socket /var/run/docker.sock http:/v1.24/images/json
[{
  "Id":"sha256:31d9a31e1dd803470c5a151b8919ef1988ac3efd44281ac59d43ad623f275dcd",
  "ParentId":"sha256:ee4603260daafe1a8c2f3b78fd760922918ab2441cbb2853ed5c439e59c52f96",
  ...
}]

Pull an image

Pull an image, like docker pull:

package main

import (
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	out, err := cli.ImagePull(ctx, "alpine", types.ImagePullOptions{})
	if err != nil {
		panic(err)
	}

	defer out.Close()

	io.Copy(os.Stdout, out)
}

import docker
client = docker.from_env()
image = client.images.pull("alpine")
print image.id

$ curl --unix-socket /var/run/docker.sock \
  -X POST "http:/v1.24/images/create?fromImage=alpine"
{"status":"Pulling from library/alpine","id":"3.1"}
{"status":"Pulling fs layer","progressDetail":{},"id":"8f13703509f7"}
{"status":"Downloading","progressDetail":{"current":32768,"total":2244027},"progress":"[\u003e                                                  ] 32.77 kB/2.244 MB","id":"8f13703509f7"}
...

Pull an image with authentication

Pull an image, like docker pull, with authentication:

Note: Credentials are sent in the clear. Docker’s official registries use HTTPS. Private registries should also be configured to use HTTPS.

package main

import (
	"encoding/base64"
	"encoding/json"
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	authConfig := types.AuthConfig{
		Username: "username",
		Password: "password",
	}
	encodedJSON, err := json.Marshal(authConfig)
	if err != nil {
		panic(err)
	}
	authStr := base64.URLEncoding.EncodeToString(encodedJSON)

	out, err := cli.ImagePull(ctx, "alpine", types.ImagePullOptions{RegistryAuth: authStr})
	if err != nil {
		panic(err)
	}

	defer out.Close()
	io.Copy(os.Stdout, out)
}

The Python SDK retrieves authentication information from the credentials store file and integrates with credential helpers. It is possible to override these credentials, but that is out of scope for this Getting Started guide. After using docker login, the Python SDK uses these credentials automatically.

import docker
client = docker.from_env()
image = client.images.pull("alpine")
print image.id

This example leaves the credentials in your shell’s history, so consider this a naive implementation. The credentials are passed as a Base-64-encoded JSON structure.

$ JSON=$(echo '{"username": "string", "password": "string", "serveraddress": "string"}' | base64)

$ curl --unix-socket /var/run/docker.sock \
  -H "Content-Type: application/tar"
  -X POST "http:/v1.24/images/create?fromImage=alpine"
  -H "X-Registry-Auth"
  -d "$JSON"
{"status":"Pulling from library/alpine","id":"3.1"}
{"status":"Pulling fs layer","progressDetail":{},"id":"8f13703509f7"}
{"status":"Downloading","progressDetail":{"current":32768,"total":2244027},"progress":"[\u003e                                                  ] 32.77 kB/2.244 MB","id":"8f13703509f7"}
...

Commit a container

Commit a container to create an image from its contents:

package main

import (
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/api/types/container"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	cli, err := client.NewEnvClient()
	if err != nil {
		panic(err)
	}

	createResp, err := cli.ContainerCreate(ctx, &container.Config{
		Image: "alpine",
		Cmd:   []string{"touch", "/helloworld"},
	}, nil, nil, "")
	if err != nil {
		panic(err)
	}

	if err := cli.ContainerStart(ctx, createResp.ID, types.ContainerStartOptions{}); err != nil {
		panic(err)
	}

	statusCh, errCh := cli.ContainerWait(ctx, createResp.ID, container.WaitConditionNotRunning)
	select {
	case err := <-errCh:
		if err != nil {
			panic(err)
		}
	case <-statusCh:
	}

	commitResp, err := cli.ContainerCommit(ctx, createResp.ID, types.ContainerCommitOptions{Reference: "helloworld"})
	if err != nil {
		panic(err)
	}

	fmt.Println(commitResp.ID)
}

import docker
client = docker.from_env()
container = client.containers.run("alpine", ["touch", "/helloworld"], detach=True)
container.wait()
image = container.commit("helloworld")
print image.id

$ docker run -d alpine touch /helloworld
0888269a9d584f0fa8fc96b3c0d8d57969ceea3a64acf47cd34eebb4744dbc52
$ curl --unix-socket /var/run/docker.sock\
  -X POST "http:/v1.24/commit?container=0888269a9d&repo=helloworld"
{"Id":"sha256:6c86a5cd4b87f2771648ce619e319f3e508394b5bfc2cdbd2d60f59d52acda6c"}
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