Bring back docker image (#1211)

* Revert "don't build docker images in CI (#1062)"

This reverts commit 1e742ff.

* update readme to mention CLI, not console

* the obvious thing would be to use install_prereqs.sh directly, but let's try this instead

* give up, attempt to run install_prerequisites.sh

* just for fun, remove sudo from install prereqs script

* also try copying the install step out of the script, but *before* cargo build

* Revert "just for fun, remove sudo from install prereqs script"

5a7503f

* use prereqs script again, this time with workarounds

* try and fix the branch name extractor

.github/workflows/docker-image.yml

@@ -0,0 +1,42 @@
+#
+# GitHub Actions configuration to automatically build and publish a Docker image
+# for Omicron.  See README for details.
+#
+name: docker-image
+on: push
+jobs:
+  docker-image:
+    runs-on: ubuntu-18.04
+    steps:
+      # actions/checkout@v2
+      - uses: actions/checkout@28c7f3d2b5162b5ddd3dfd9a45aa55eaf396478b
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+      - name: Login to GitHub Packages Docker Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Extract branch name
+        shell: bash
+        run: echo "##[set-output name=branch;]$(echo ${GITHUB_REF_NAME//\//-})"
+        id: extract_branch
+      - name: Build and push
+        # This pushes a docker image to github's container registry.
+        # It is not a public image by default.
+        # The docs are here: https://github.com/docker/build-push-action
+        uses: docker/build-push-action@9379083e426e2e84abb80c8c091f5cdeb7d3fd7a
+        with:
+          push: ${{ ! startsWith(github.ref, 'refs/heads/dependabot') }}
+          file: ./Dockerfile
+          tags: ghcr.io/${{ github.repository_owner }}/omicron:${{ steps.extract_branch.outputs.branch }},ghcr.io/${{ github.repository_owner }}/omicron:${{ github.sha }}
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache

Dockerfile

@@ -0,0 +1,47 @@
+# 
+# Dockerfile: build a Docker image for Omicron.  This is used by the console for
+# prototyping and development.  This will not be used for deployment to a real 
+# rack.
+# 
+# ------------------------------------------------------------------------------
+# Cargo Build Stage
+# ------------------------------------------------------------------------------
+
+FROM rust:latest as cargo-build
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+WORKDIR /usr/src/omicron
+
+COPY . .
+
+WORKDIR /usr/src/omicron
+
+# sudo and path thing are only needed to get prereqs script to run
+ENV PATH=/usr/src/omicron/out/cockroachdb/bin:/usr/src/omicron/out/clickhouse:${PATH} 
+RUN apt-get update && apt-get install -y sudo --no-install-recommends && rm -rf /var/lib/apt/lists/*
+RUN tools/install_prerequisites.sh -y
+
+RUN cargo build --release
+
+# ------------------------------------------------------------------------------
+# Final Stage
+# ------------------------------------------------------------------------------
+
+FROM debian:sid-slim
+
+RUN apt-get update && apt-get install -y \
+	ca-certificates \
+	libpq5 \
+	libssl1.1 \
+	libsqlite3-0 \
+	--no-install-recommends \
+	&& rm -rf /var/lib/apt/lists/*
+
+
+COPY --from=cargo-build /usr/src/omicron/target/release/nexus /usr/bin/nexus
+COPY --from=cargo-build /usr/src/omicron/target/release/omicron-dev /usr/bin/omicron-dev
+COPY --from=cargo-build /usr/src/omicron/target/release/omicron-package /usr/bin/omicron-package
+COPY --from=cargo-build /usr/src/omicron/target/release/sled-agent-sim /usr/bin/sled-agent-sim
+
+CMD ["sled-agent-sim"]

README.adoc

@@ -49,6 +49,10 @@ This mode of operation will be used in production.
 
 See: xref:docs/how-to-run.adoc[].
 
+== Docker image
+
+This repo includes a Dockerfile that builds an image containing the Nexus and sled agent.  There's a GitHub Actions workflow that builds and publishes the Docker image.  This is used by [cli](https://github.com/oxidecomputer/cli) for testing. This is **not** the way Omicron will be deployed on production systems, but it's a useful vehicle for working with it.
+
 == Configuration reference
 
 `nexus` requires a TOML configuration file.  There's an example in