tutorials/test: add test container

Add test container to easily spot if users are struggling starting
privileged containers managing Linux network namespaces.

Hopefully this will never fail...

Author: msune

.github/workflows/publish_docker_images.yaml

@@ -11,6 +11,7 @@ permissions:
 env:
   PLATFORMS: linux/amd64,linux/arm64
   BUILD_DIRS: |
+    tutorials/test/
     tutorials/net/mtu/
 
 jobs:

tutorials/test/BANNER

@@ -0,0 +1,7 @@
+=================================================
+     🐧  bitpuff.io tutorial setup test  🐧
+=================================================
+This container tests that your docker setup is
+correct, and that privileged containers can
+create Linux network namespaces (NSs).
+-------------------------------------------------

tutorials/test/README.md

@@ -0,0 +1,10 @@
+## Test setup container
+
+This container image tests that your docker setup is correct, and that privileged
+containers can create [Linux Network namespaces](https://man7.org/linux/man-pages/man7/network_namespaces.7.html).
+
+## How to use it
+
+```
+docker run --privileged ghcr.io/bitpuff-io/tutorials.test
+```

tutorials/test/docker/Dockerfile

@@ -0,0 +1,19 @@
+FROM debian:latest
+
+LABEL maintainer="Marc Sune <[email protected]>"
+LABEL version="latest"
+LABEL description="bitpuff.io MTU setup test"
+LABEL org.opencontainers.image.authors="Marc Sune <[email protected]>"
+LABEL org.opencontainers.image.url="https://github.com/bitpuff-io/code/"
+LABEL org.opencontainers.image.documentation="https://bitpuff.io/tutorials/setup/"
+LABEL org.opencontainers.image.source="https://github.com/bitpuff-io/code/"
+LABEL org.opencontainers.image.licenses="BSD"
+
+RUN apt update && apt install -y --no-install-recommends \
+	iproute2       \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN mkdir /bp
+COPY . /bp
+WORKDIR /root
+CMD ["/bp/entrypoint.sh"]

tutorials/test/docker/tag

@@ -0,0 +1 @@
+tutorials.test

tutorials/test/entrypoint.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -euo pipefail
+
+cat /bp/BANNER
+
+echo "[INFO] Creating namespace 'bp_test_ns'..."
+ip netns add bp_test_ns
+
+echo "[INFO] Executing command inside the NS..."
+ip netns exec bp_test_ns echo "Hello world!"
+
+echo "[INFO] All is good!"