docker

docs/10-prerequisities/30-docker/20-crossplatform-build.md

@@ -5,3 +5,46 @@ description: How to build crossplatform Docker images
 ---
 
 # Crossplatform docker build
+
+A docker image can be build for a desired platform by adding the `--platform` parameter:
+
+```bash
+docker build . --file Dockerfile --tag <my_tag> --platform=arm64
+```
+
+The crossplatform build is facilitated by QEMU.
+Expect a run-time approx. 10x slower than for the native platform.
+
+## Multi-platform docker build
+
+Multi-platform images can be built using the `dockerx` multiplatform builder.
+First, instantiate a multiplatform builder and set it to be the default:
+
+```bash
+docker buildx create --name container-builder --driver docker-container --bootstrap --use
+```
+
+Then, build an image using the `buildx` command (which uses the selected builder) and supply the `--platform` parameter with the list of the desired platforms:
+
+```bash
+docker buildx build . --file Dockerfile --tag $REGISTRY/$LOCAL_TAG --platform=linux/arm64,linux/amd64 --push
+```
+
+### Listing the available docker builders
+
+```bash
+docker buildx list
+```
+
+```
+NAME/NODE                DRIVER/ENDPOINT                   STATUS    BUILDKIT   PLATFORMS
+container-builder        docker-container
+ \_ container-builder0    \_ unix:///var/run/docker.sock   running   v0.16.0    linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/amd64/v4, linux/arm64, linux/riscv64, linux/ppc64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6
+ default*                 docker
+  \_ default               \_ default                       running   v0.16.0    linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/amd64/v4, linux/arm64, linux/riscv64, linux/ppc64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6
+````
+
+If you want to switch back to the default docker builder, select it then by issuing
+```bash
+docker buildx use default
+```