adds Docker outside of Docker

Dockerfile

@@ -227,19 +227,16 @@ RUN curl https://packagecloud.io/install/repositories/cs50/repo/script.deb.sh |
 RUN apt update && \
     apt install --no-install-recommends --no-install-suggests --yes \
         ca-certificates \
-        curl && \
+        curl \
+        socat && \
     install -d /etc/apt/keyrings -m 0755 && \
     curl --fail --location --show-error --silent https://download.docker.com/linux/ubuntu/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/ubuntu $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null && \
     apt update && \
     sudo apt install --no-install-recommends --no-install-suggests --yes \
-        containerd.io \
-        docker-buildx-plugin \
-        docker-ce \
-        docker-ce-cli \
-        docker-compose-plugin && \
-    groupadd --force docker
+        docker-ce-cli && \
+    groupadd docker
 
 
 # Install Python packages
@@ -293,7 +290,6 @@ ONBUILD ARG VCS_REF
 ONBUILD RUN echo "$VCS_REF" >> /etc/issue
 ONBUILD USER ubuntu
 
-
 # Set user
 USER ubuntu
 WORKDIR /home/ubuntu

Makefile

@@ -3,19 +3,15 @@ default: run
 
 build:
 	docker build --build-arg VCS_REF="$(shell git rev-parse HEAD)" --tag cs50/cli .
-	$(MAKE) squash
 
 depends:
 	pip3 install docker-squash
 
 rebuild:
 	docker build --no-cache --tag cs50/cli .
-	$(MAKE) squash
 
 run:
-	docker run --env LANG="$(LANG)" --interactive --privileged --publish-all --rm --security-opt seccomp=unconfined --tty --volume "$(PWD)":/home/ubuntu cs50/cli bash --login || true
+	docker run --env LANG="$(LANG)" --interactive --publish-all --rm --security-opt seccomp=unconfined --tty --volume "$(PWD)":/home/ubuntu --volume /var/run/docker.sock:/var/run/docker-host.sock cs50/cli bash --login || true
 
 squash: depends
-	docker images cs50/cli
 	docker-squash --tag cs50/cli cs50/cli
-	docker images cs50/cli

etc/init.d/docker

@@ -0,0 +1,41 @@
+#!/bin/bash
+
+# Adapted from https://github.com/devcontainers/features/blob/main/src/docker-outside-of-docker/install.sh. 
+# If docker-ce is installed, shadows its own.
+
+set -e
+
+SOURCE_SOCKET=/var/run/docker-host.sock
+TARGET_SOCKET=/var/run/docker.sock
+SOCAT_PID=/tmp/docker.pid
+
+case "$1" in
+  start)
+    echo "Starting Docker"
+    socat UNIX-LISTEN:${TARGET_SOCKET},fork,mode=660,group=docker UNIX-CONNECT:${SOURCE_SOCKET} & echo "$!" > "$SOCAT_PID"
+    ;;
+  stop)
+    echo "Stopping Docker"
+    kill -9 $(cat "$SOCAT_PID") 2> /dev/null
+    rm --force "$SOCAT_PID" "$TARGET_SOCKET"
+    ;;
+  restart)
+    $0 stop
+    $0 start
+    ;;
+  status)
+    if [[ ! -f "${SOCAT_PID}" ]] || ! ps -p $(cat "$SOCAT_PID") > /dev/null; then
+      echo "Docker is not running"
+      exit 1
+    else
+      echo "Docker is running"
+      exit 0
+    fi
+    ;;
+  *)
+    echo "Usage: $0 {start|stop|restart|status}"
+    exit 1
+    ;;
+esac
+
+exit 0