Add Docker to rails-app

Author: lcreid

Linux/compose.override.yml

@@ -2,6 +2,8 @@
 
 services:
   web:
+    group_add:
+      - "140"
     volumes:
       - ~/.gitconfig:/home/dev/.gitconfig
       # - /etc/passwd:/etc/passwd:ro

rails-app/Dockerfile

@@ -21,6 +21,24 @@ RUN curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | gpg -
 
 RUN apt-get update && apt-get install libvips-dev -y -q --no-install-recommends && apt-get clean && rm -rf /var/lib/apt/lists/*
 
+# The following is so part of what we need to run `kamal deploy` inside the container. Rafael says running
+# Kamal inside the container is the intended use.
+# You need to have the Docker executables in the container, plus the right volume mounts and permissions
+# in `compose.yml` or `compose.override.yml` so the executables can use the Docker engine running on the host.
+# All this sounds like it's very *nix-specific.
+RUN apt-get update && \
+    curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc && \
+    chmod a+r /etc/apt/keyrings/docker.asc && \
+    echo \
+        "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian \
+        $(. /etc/os-release && echo "$VERSION_CODENAME") stable" > /etc/apt/sources.list.d/docker.list && \
+    apt-get update && \
+    apt-get install docker-buildx-plugin -y -q --no-install-recommends && \
+    apt-get update && \
+    apt-get install docker-ce-cli -y -q --no-install-recommends && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
 # `rails-app` is useful for other things, like Jekyll, so let's install foreman as well.
 # Rails needs it anyway, at least in some configurations, so this saves an install on-the-fly.
 USER dev