Added buildx to allow multi-arch builds

Squashed commit of the following:

commit f3d42ceebe3f209645dc44b9e1ea956339c32968
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:48:23 2021 +0100

    Only build master since rpi3 is no longer needed

commit 32e213d65955291fa38d20c77e74aa30cf25cd24
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:46:40 2021 +0100

    Added dockerhub login

commit 960c44c7148073cfbee617be3019fb399d1fc0b1
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:38:21 2021 +0100

    Added ARCH to Dockerfile

commit fad35cd700dcf7a4c4ee5ac7eeea89f33871eaab
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:30:30 2021 +0100

    don't push in buildx

commit 9cd85b6787ec552d5dee393a40137fa3ed9cb94e
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:28:09 2021 +0100

    added context

commit 07fb2b320463dc495c4e69f40bb524bcc0ebd15a
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:20:02 2021 +0100

    Added experimental

commit 99b352dad13aca54f49fb56f0fb19a921cd81c9d
Author: 1O <2408212-1O@users.noreply.gitlab.com>
Date:   Sun Jan 24 19:16:59 2021 +0100

    Added buildx

.gitlab-ci.yml

@@ -7,6 +7,9 @@ variables:
   # see https://gitlab.com/gitlab-org/gitlab-runner/issues/4501
   DOCKER_DRIVER: overlay2
   DOCKER_TLS_CERTDIR: "/certs"
+  # See https://github.com/docker/buildx/releases
+  BUILDX_VERSION: v0.5.1
+  BUILDX_ARCH: linux-amd64
 
 .docker_login: &docker_login
   docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
@@ -18,37 +21,29 @@ variables:
   stage: build:docker
   image: docker:latest
   services:
-    - docker:dind
+    - name: docker:dind
+      command: ["--experimental"]
   tags:
     - shared
+  before_script:
+    - apk add curl
+    - mkdir -p ~/.docker/cli-plugins
+    - curl -sSLo ~/.docker/cli-plugins/docker-buildx https://github.com/docker/buildx/releases/download/$BUILDX_VERSION/buildx-$BUILDX_VERSION.$BUILDX_ARCH 
+    - chmod +x ~/.docker/cli-plugins/docker-buildx
+    - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+    - docker context create my-context
+    - docker buildx create --use my-context
+    - docker info
 
 build_master:
   <<: *docker_build
   script:
     - *docker_login
-    - docker build --pull -t "$IMAGE_NAME" -t "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}" .
-    - docker push "$IMAGE_NAME"
     - *dockerhub_login
-    - docker push "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}"
-  only:
-    refs:
-      - master
-      - tags
-    changes:
-      - Dockerfile
-      - backup.sh
-      - entrypoint.sh
-
-build_master_rpi3:
-  <<: *docker_build
-  script:
-    - *docker_login
-    - docker build --pull -t "$IMAGE_NAME:rpi3" -t "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}-rpi3" .
-    - docker push "$IMAGE_NAME:rpi3"
-    - *dockerhub_login
-    - docker push "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}-rpi3"
-  tags:
-    - rpi3
+    #- docker build --pull -t "$IMAGE_NAME" -t "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}" .
+    - docker buildx build --push --platform linux/arm/v7,linux/arm64/v8,linux/amd64 -t "$IMAGE_NAME" -t "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}" .
+    #- docker push "$IMAGE_NAME"
+    #- docker push "$IMAGE_NAME_DOCKERHUB:${CI_COMMIT_TAG:-latest}"
   only:
     refs:
       - master
@@ -62,8 +57,9 @@ build:
   <<: *docker_build
   script:
     - *docker_login
-    - docker build --pull -t "$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG/bw_backup:${CI_COMMIT_TAG:-latest}" .
-    - docker push "$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG/bw_backup:${CI_COMMIT_TAG:-latest}"
+    #- docker build --pull -t "$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG/bw_backup:${CI_COMMIT_TAG:-latest}" .
+    - docker buildx build --push --platform linux/arm/v7,linux/arm64/v8,linux/amd64 --tag "$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG/bw_backup:${CI_COMMIT_TAG:-latest}" .
+    #- docker push "$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG/bw_backup:${CI_COMMIT_TAG:-latest}"
   except:
     - master
 

Dockerfile

@@ -1,4 +1,5 @@
-FROM alpine:latest
+ARG ARCH=
+FROM ${ARCH}alpine:latest
 
 RUN addgroup -S app && adduser -S -G app app