docker build · Knowledge & Memory Center

Command

Build and tag

SHELL

1docker build -t <image>:<tag> .

2

3# build a specific stage of a multi-stage Dockerfile

4docker build --target <stage-name> -t <image>:<tag> .

5

6# rebuild ignoring the layer cache

7docker build --no-cache -t <image>:<tag> .

Tip

Order Dockerfile instructions from least- to most-often-changing (dependencies before source code) so a source change doesn't invalidate the dependency-install layer's cache.

Flags explained

Flag reference

SHELL

1-t name:tag # name the image (repeatable)

2-f path/Dockerfile # use a Dockerfile elsewhere

3--build-arg KEY=value # value for an ARG in the Dockerfile

4--target <stage> # stop at a multi-stage stage

5--no-cache # ignore all cached layers

6--pull # always fetch a newer base image

7--platform linux/amd64 # build for another CPU architecture

8--progress=plain # full, non-collapsed build output

9. # the build context (files sent to the builder)

Everyday examples

Examples

SHELL

1# Build with a version arg and two tags

2docker build --build-arg APP_VERSION=1.4.2 -t myapp:1.4.2 -t myapp:latest .

3

4# Dockerfile in a subfolder, context at the repo root

5docker build -f docker/api.Dockerfile -t api .

6

7# Multi-arch build and push (buildx)

8docker buildx build --platform linux/amd64,linux/arm64 \

9 -t <user>/myapp:1.4.2 --push .

10

11# Debug a failing step with full output

12docker build --progress=plain --no-cache .

Build context & .dockerignore

Everything in the context folder is sent to the builder before the first step runs. A missing .dockerignore makes builds slow and can leak secrets into the image.

.dockerignore

TEXT

1.git

2node_modules

3dist

4*.log

5.env

6.env.*

7Dockerfile

8docker-compose*.yml

!

Never COPY .env files or keys into an image: anyone who can pull the image can read every layer. Pass secrets at runtime or use --secret.