World D2: Recipes

Your first recipe: FROM, COPY, CMD

You will learn: to write a three-line Dockerfile and bake it into an image.

Checked with Docker Engine 29 on 31 Oct 2026

The problem

Your hello app works on your laptop. On Aina’s laptop it crashes. She has an older Node. What fixes this for good?

Watch

~/hello $ cat DockerfileFROM node:24-alpineCOPY hello.js /hello.jsCMD ["node", "/hello.js"]

Your laptop`~/hello`

No open hatches

Lunchboxes (containers)

No containers yet

Frozen packs (images)

node:24-alpine4 layers · 244MB

A is a recipe for an image. FROM picks a frozen base pack. COPY adds your food. CMD says what to do when the box opens.

Try it

Put the recipe in order. The top line runs first.

First line at the top. Put these in order. Use the arrows, or drag.

COPY hello.js /hello.js
FROM node:24-alpine
CMD ["node", "/hello.js"]

Watch

~/hello $ docker build -t hello:1.0 .[+] Building 0.1s (7/7) FINISHED                                  docker:default => [internal] load build definition from Dockerfile                        0.0s => => transferring dockerfile: 107B                                        0.0s => [internal] load metadata for docker.io/library/node:24-alpine           0.0s => [internal] load .dockerignore                                           0.0s => => transferring context: 2B                                             0.0s => [1/2] FROM docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => => resolve docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => [internal] load build context                                           0.0s => => transferring context: 141B                                           0.0s => [2/2] COPY hello.js /hello.js                                           0.0s => exporting to image                                                      0.1s => => exporting layers                                                     0.0s => => exporting manifest sha256:44e03045f4c8b90ad6efee4446fa5b308798c4009  0.0s => => exporting config sha256:9c60021cdc96a7a0c482f11cac463756a3dab506a44  0.0s => => exporting attestation manifest sha256:069105ba22e077bc68b712e352a68  0.0s => => exporting manifest list sha256:7063ee281c8ba71514cc623bfa4a8d36ca2d  0.0s => => naming to docker.io/library/hello:1.0                                0.0s => => unpacking to docker.io/library/hello:1.0                             0.0s~/hello $ docker images hello                                        i Info →   U  In UseIMAGE       ID             DISK USAGE   CONTENT SIZE   EXTRAhello:1.0   7063ee281c8b        244MB         62.5MB

Your laptop`~/hello`

No open hatches

Lunchboxes (containers)

No containers yet

Frozen packs (images)

node:24-alpine4 layers · 244MB

docker build -t hello:1.0 . bakes the recipe into an image. -t gives it a name and a tag. The dot means “use this folder”.

Try it

Your turn. Build the image, then run it once.

Your laptop`~/hello`

No open hatches

Lunchboxes (containers)

No containers yet

Frozen packs (images)

node:24-alpine4 layers · 244MB

Hint

Type docker build -t hello:1.0 . first. Then docker run --rm hello:1.0.

Predict

You change the message in hello.js. Then you run hello:1.0 again. What prints?

Check

~/hello $ docker build -t hello:1.0 .[+] Building 0.1s (7/7) FINISHED                                  docker:default => [internal] load build definition from Dockerfile                        0.0s => => transferring dockerfile: 107B                                        0.0s => [internal] load metadata for docker.io/library/node:24-alpine           0.0s => [internal] load .dockerignore                                           0.0s => => transferring context: 2B                                             0.0s => [1/2] FROM docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => => resolve docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => [internal] load build context                                           0.0s => => transferring context: 141B                                           0.0s => [2/2] COPY hello.js /hello.js                                           0.0s => exporting to image                                                      0.1s => => exporting layers                                                     0.0s => => exporting manifest sha256:44e03045f4c8b90ad6efee4446fa5b308798c4009  0.0s => => exporting config sha256:9c60021cdc96a7a0c482f11cac463756a3dab506a44  0.0s => => exporting attestation manifest sha256:069105ba22e077bc68b712e352a68  0.0s => => exporting manifest list sha256:7063ee281c8ba71514cc623bfa4a8d36ca2d  0.0s => => naming to docker.io/library/hello:1.0                                0.0s => => unpacking to docker.io/library/hello:1.0                             0.0s~/hello $ echo "console.log('Hai lagi!');" > hello.js~/hello $ docker run --rm hello:1.0Hello from Kedai Kancil!~/hello $ docker build -t hello:1.1 .[+] Building 0.1s (7/7) FINISHED                                  docker:default => [internal] load build definition from Dockerfile                        0.0s => => transferring dockerfile: 107B                                        0.0s => [internal] load metadata for docker.io/library/node:24-alpine           0.0s => [internal] load .dockerignore                                           0.0s => => transferring context: 2B                                             0.0s => [1/2] FROM docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => => resolve docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6  0.0s => [internal] load build context                                           0.0s => => transferring context: 126B                                           0.0s => [2/2] COPY hello.js /hello.js                                           0.0s => exporting to image                                                      0.1s => => exporting layers                                                     0.0s => => exporting manifest sha256:c6ef1a96f61d1ec6804b4ba4bfeb1e1ed2accc40f  0.0s => => exporting config sha256:d242cdff7c93b75afc3520cbd6f47f57a0df440c8d9  0.0s => => exporting attestation manifest sha256:b6268118f4da4929ec6a35bb5cf10  0.0s => => exporting manifest list sha256:b602534f7b4cc1dc5d80849b1a58d9348608  0.0s => => naming to docker.io/library/hello:1.1                                0.0s => => unpacking to docker.io/library/hello:1.1                             0.0s~/hello $ docker run --rm hello:1.1Hai lagi!

After hello.js changes, hello:1.0 still prints Hello from Kedai Kancil. A new build, hello:1.1, prints Hai lagi. Docker transcript: $ docker build -t hello:1.0 . [+] Building 0.1s (7/7) FINISHED docker:default => [internal] load build definition from Dockerfile 0.0s => => transferring dockerfile: 107B 0.0s => [internal] load metadata for docker.io/library/node:24-alpine 0.0s => [internal] load .dockerignore 0.0s => => transferring context: 2B 0.0s => [1/2] FROM docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6 0.0s => => resolve docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6 0.0s => [internal] load build context 0.0s => => transferring context: 141B 0.0s => [2/2] COPY hello.js /hello.js 0.0s => exporting to image 0.1s => => exporting layers 0.0s => => exporting manifest sha256:44e03045f4c8b90ad6efee4446fa5b308798c4009 0.0s => => exporting config sha256:9c60021cdc96a7a0c482f11cac463756a3dab506a44 0.0s => => exporting attestation manifest sha256:069105ba22e077bc68b712e352a68 0.0s => => exporting manifest list sha256:7063ee281c8ba71514cc623bfa4a8d36ca2d 0.0s => => naming to docker.io/library/hello:1.0 0.0s => => unpacking to docker.io/library/hello:1.0 0.0s $ echo "console.log('Hai lagi!');" > hello.js $ docker run --rm hello:1.0 Hello from Kedai Kancil! $ docker build -t hello:1.1 . [+] Building 0.1s (7/7) FINISHED docker:default => [internal] load build definition from Dockerfile 0.0s => => transferring dockerfile: 107B 0.0s => [internal] load metadata for docker.io/library/node:24-alpine 0.0s => [internal] load .dockerignore 0.0s => => transferring context: 2B 0.0s => [1/2] FROM docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6 0.0s => => resolve docker.io/library/node:24-alpine@sha256:8a32c8cf649a49915a6 0.0s => [internal] load build context 0.0s => => transferring context: 126B 0.0s => [2/2] COPY hello.js /hello.js 0.0s => exporting to image 0.1s => => exporting layers 0.0s => => exporting manifest sha256:c6ef1a96f61d1ec6804b4ba4bfeb1e1ed2accc40f 0.0s => => exporting config sha256:d242cdff7c93b75afc3520cbd6f47f57a0df440c8d9 0.0s => => exporting attestation manifest sha256:b6268118f4da4929ec6a35bb5cf10 0.0s => => exporting manifest list sha256:b602534f7b4cc1dc5d80849b1a58d9348608 0.0s => => naming to docker.io/library/hello:1.1 0.0s => => unpacking to docker.io/library/hello:1.1 0.0s $ docker run --rm hello:1.1 Hai lagi!

Your laptop`~/hello`

No open hatches

Lunchboxes (containers)

No containers yet

Frozen packs (images)

node:24-alpine4 layers · 244MB

The old pack still says hello. A new build packs the new file. Change the recipe or the food? Build again.

You did it!

You can now write a recipe and bake it into an image.

Go deeper (optional)

A website on the nginx base needs no CMD. The base pack already has one. docker build reads the file called Dockerfile in the folder you name.

Real rep (optional), on your own computer:

Real mission

Make a folder with a hello.js that prints one line.
mkdir hello && cd hello
Add a Dockerfile with the three lines from this lesson.
Build it.
docker build -t hello:1.0 .
Run it once and clean up.
docker run --rm hello:1.0

0 of 4 steps done · Your ticks are saved.

Your first recipe: FROM, COPY, CMD

Your laptop~/hello

Lunchboxes (containers)

Frozen packs (images)

Your laptop~/hello

Lunchboxes (containers)

Frozen packs (images)

Your laptop~/hello

Lunchboxes (containers)

Frozen packs (images)

Your laptop~/hello

Lunchboxes (containers)

Frozen packs (images)

Your laptop`~/hello`

Your laptop`~/hello`

Your laptop`~/hello`

Your laptop`~/hello`