Podman support

.dockerignore

@@ -13,3 +13,6 @@ CHRIS_REMOTE_FS
 swarm/prod/secrets
 kubernetes/prod/base/secrets
 dc.out
+
+# created by `just prefer`
+.preference

.github/workflows/ci.yml

@@ -11,9 +11,20 @@ on:
 jobs:
   test:
     runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        engine: [ 'docker', 'podman' ]
     steps:
       - uses: actions/checkout@v4
       - uses: taiki-e/install-action@just
+      - name: Start podman daemon
+        if: matrix.engine == 'podman'
+        run: |
+          set -ex
+          systemctl --user start podman.service
+          just get-socket
+      - name: Set preference to use ${{ matrix.engine }}
+        run: just prefer ${{ matrix.engine }}
       - name: Build development image
         run: just build
       - name: Pull other images

.gitignore

@@ -18,3 +18,6 @@ venv
 # created by dev container bc UBI sets HOME to the project src dir
 chris_backend/.config
 chris_backend/.bash_history
+
+# created by `just prefer`
+.preference

README.md

@@ -36,7 +36,7 @@ The HTTP API primarily supports the [collection+json](http://amundsen.com/media-
 
 Development is mainly supported on Linux. MacOS and WSL on Windows also work (because Docker Desktop is a Linux VM). You will need at least 8GM RAM, 20GB disk space, and a good internet connection.
 
-Install Docker (version 27 or above), Docker Compose, and [just](https://github.com/casey/just?tab=readme-ov-file#installation).
+Install Docker (version 27 or above) or Podman (version 5.2 or above), Docker Compose, and [just](https://github.com/casey/just?tab=readme-ov-file#installation).
 
 <details>
 <summary>
@@ -54,6 +54,28 @@ Docker Installation Instructions
 
 </details>
 
+<details>
+<summary>
+Podman Setup Instructions
+</summary>
+
+Rootless Podman is supported. You must install and configure Podman to use `docker-compose`, _not_ `podman-compose`. `podman-compose` is missing features, see issues [#575](https://github.com/containers/podman-compose/issues/575) and [#866](https://github.com/containers/podman-compose/issues/866).
+
+A Podman daemon must be running, because _ChRIS_ runs containers of its own. To start the Podman daemon on Linux, run
+
+```shell
+systemctl --user start podman.service
+```
+
+If both Podman and Docker are installed, Podman will be used by default. A preference to use either Podman or Docker can be set by running
+
+```shell
+just prefer podman  # or
+just prefer docker
+```
+
+</details>
+
 ### Just Commands
 
 Development is handled by [`just`](https://just.systems).

docker-compose_just.yml

@@ -8,7 +8,7 @@ services:
       - tools
     volumes:
       - "./chrisomatic:/etc/chrisomatic:ro"
-      - "/var/run/docker.sock:/var/run/docker.sock"
+      - "${DOCKER_SOCK:-/var/run/docker.sock}:/var/run/docker.sock"
     working_dir: /etc/chrisomatic
     userns_mode: host
     depends_on:
@@ -139,7 +139,7 @@ services:
       SECRET_KEY: secret
       REMOVE_JOBS: "yes"
     volumes:
-      - /var/run/docker.sock:/var/run/docker.sock
+      - "${DOCKER_SOCK:-/var/run/docker.sock}:/var/run/docker.sock"
     depends_on:
       - pfcon
     ports:

justfile

@@ -78,4 +78,45 @@ run +command:
 
 # docker-compose ... helper function.
 docker-compose +command:
-    env UID=$(id -u) GID=$(id -g) docker compose -f '{{ compose_file }}' {{command}}
+    env UID=$(id -u) GID=$(id -g) DOCKER_SOCK=$(just get-socket) $(just get-engine) compose -f '{{ compose_file }}' {{command}}
+
+# Get the container engine to use (docker or podman)
+get-engine:
+    @if [ -f '.preference' ]; then           \
+      cat .preference && exit 0;             \
+    elif type podman > /dev/null 2>&1; then  \
+      echo podman;                           \
+    else                                     \
+      echo docker;                           \
+    fi                                       \
+
+# Get the docker daemon socket
+get-socket:
+    @if [ "$(just get-engine)" = 'podman' ]; then     \
+      just get-podman-socket;                         \
+    else                                              \
+      echo '/var/lib/docker.sock';                    \
+    fi
+
+get-podman-socket: check-podman-socket
+    @podman info --format '{{{{ .Host.RemoteSocket.Path }}'
+
+# Ensure that the podman daemon is running.
+check-podman-socket:
+    @if [ "$(podman info --format '{{{{ .Host.RemoteSocket.Exists }}')" != 'true' ]; then       \
+      echo 'Podman daemon not running. Please run `systemctl --user start podman.service`';      \
+      exit 1;                                                                                    \
+    fi
+
+# Set a preference for using either Docker or Podman.
+prefer docker_or_podman:
+    @[ '{{docker_or_podman}}' = 'docker' ] || [ '{{docker_or_podman}}' = 'podman' ] \
+        || ( \
+            >&2 echo 'argument must be either "docker" or "podman"'; \
+            exit 1 \
+        )
+    echo '{{docker_or_podman}}' > .preference
+
+# Remove your preference for Docker or Podman.
+unset-preference:
+    rm -f .preference