Build rtorrent Docker image on Debian 12 slim

- Create multi-stage Dockerfile for libtorrent/rtorrent compilation
- Set up runtime image with binaries, config, and entrypoint script
- Implement Makefile and docker-compose for build/cleanup processes
- Entrypoint script for user creation and config setup

Dockerfile

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+FROM debian:12-slim AS build
+
+ARG LIBTORRENT_VERSION="0.13.8"
+ARG LIBTORRENT_HASH="ed115a28f4ae8cfcd33b94a597c076ca74fd549867a26e4fac9505c27288e983"
+ARG LIBTORRENT_URL="https://github.com/rakshasa/rtorrent-archive/raw/master/libtorrent-${LIBTORRENT_VERSION}.tar.gz"
+
+ARG RTORRENT_VERSION="0.9.8"
+ARG RTORRENT_HASH="9edf0304bf142215d3bc85a0771446b6a72d0ad8218efbe184b41e4c9c7542af"
+ARG RTORRENT_URL="https://github.com/rakshasa/rtorrent-archive/raw/master/rtorrent-${RTORRENT_VERSION}.tar.gz"
+
+RUN apt-get update && \
+    apt-get install -y \
+        build-essential \
+        curl \
+        libcurl4-openssl-dev \
+        libncursesw5-dev \
+        libssl-dev \
+        pkg-config \
+        zlib1g-dev && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN curl -s -o "/tmp/libtorrent-${LIBTORRENT_VERSION}.tar.gz" -L "$LIBTORRENT_URL" && \
+    FILE_HASH="$(sha256sum /tmp/libtorrent-${LIBTORRENT_VERSION}.tar.gz | cut -d' ' -f1)" && \
+    echo hey; \
+    du -sh "/tmp/libtorrent-${LIBTORRENT_VERSION}.tar.gz"; \
+    if [ ! "$LIBTORRENT_HASH" = "$FILE_HASH" ]; then \
+        echo "SHA256 verification failed!" && \
+        echo -e "EXPECTED:\t$LIBTORRENT_HASH" && \
+        echo -e "ACTUAL:\t$FILE_HASH" && \
+        exit 1; \
+    fi && \
+    tar -xzvf "/tmp/libtorrent-${LIBTORRENT_VERSION}.tar.gz" -C /tmp/ && \
+    rm -rf "/tmp/libtorrent-${LIBTORRENT_VERSION}.tar.gz"
+
+WORKDIR "/tmp/libtorrent-${LIBTORRENT_VERSION}"
+
+RUN ./configure && \
+    make && \
+    make install
+
+RUN curl -s -o "/tmp/rtorrent-${RTORRENT_VERSION}.tar.gz" -L "$RTORRENT_URL" && \
+    FILE_HASH="$(sha256sum /tmp/rtorrent-${RTORRENT_VERSION}.tar.gz | cut -d' ' -f1)" && \
+    if [ ! "$RTORRENT_HASH" = "$FILE_HASH" ]; then \
+        echo "SHA256 verification failed!" && \
+        echo -e "EXPECTED:\t$RTORRENT_HASH" && \
+        echo -e "ACTUAL:\t$FILE_HASH" && \
+        exit 1; \
+    fi && \
+    tar -xzvf "/tmp/rtorrent-${RTORRENT_VERSION}.tar.gz" -C /tmp/ && \
+    rm -rf "/tmp/rtorrent-${RTORRENT_VERSION}.tar.gz"
+
+WORKDIR "/tmp/rtorrent-${RTORRENT_VERSION}"
+
+RUN ./configure && \
+    make && \
+    make install
+
+RUN curl -s -L "https://raw.githubusercontent.com/wiki/rakshasa/rtorrent/CONFIG-Template.md" \
+        | sed -ne "/^######/,/^### END/p" \
+        | sed -re "s:/home/USERNAME:/home/rtorrent:" > /tmp/rtorrent.rc.template
+
+FROM debian:12-slim AS runtime
+
+COPY --from=build /usr/local/lib/libtorrent.so* /usr/local/lib/
+COPY --from=build /usr/local/bin/rtorrent /usr/local/bin/
+COPY --from=build /tmp/rtorrent.rc.template /tmp/rtorrent.rc.template
+
+RUN apt-get update && \
+    apt-get install -y \
+        libcurl4 \
+        libncursesw6 && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+COPY entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+ENTRYPOINT ["entrypoint.sh"]

Makefile

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+DOCKER_BUILDKIT ?= 1
+BUILDKIT_PROGRESS ?= auto
+
+DOCKER_COMPOSE_OPTS = BUILDX_GIT_LABELS=full \
+	DOCKER_BUILDKIT=$(DOCKER_BUILDKIT) \
+	BUILDKIT_PROGRESS=$(BUILDKIT_PROGRESS)
+
+DOCKER_COMPOSE_BUILD = $(DOCKER_COMPOSE_OPTS) docker compose -f docker-compose.build.yml build
+
+PRUNE_IMAGES = \
+	localhost/rtorrent:latest
+
+.PHONY: default
+
+default:
+	$(DOCKER_COMPOSE_BUILD) rtorrent
+
+clean:
+	docker image rm $(PRUNE_IMAGES) || true
+	docker builder prune -f

docker-compose.build.yml

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+services:
+  rtorrent:
+    build:
+      context: .
+    image: ${IMAGE:-localhost/rtorrent}:${TAG:-latest}

entrypoint.sh

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+#!/bin/bash
+set -eu
+
+# GID/UID
+USER_ID=${GUID:-1000}
+GROUP_ID=${PGID:-1000}
+
+# Create group/user
+getent group rtorrent >/dev/null || groupadd -g "$GROUP_ID" rtorrent
+id -u rtorrent &>/dev/null || \
+    useradd -m -u "$USER_ID" -g rtorrent -s /bin/bash rtorrent
+
+# Update group/user IDs
+groupmod -o -g "$GROUP_ID" rtorrent
+usermod -o -u "$USER_ID" rtorrent 2>/dev/null
+
+# Copy default config
+if [ ! -e /home/rtorrent/.rtorrent.rc ]; then
+    cp /tmp/rtorrent.rc.template /home/rtorrent/.rtorrent.rc
+    chown rtorrent:rtorrent /home/rtorrent/.rtorrent.rc
+fi
+
+# Execute as the rtorrent user
+su - rtorrent -c "rtorrent"