Handle SIGTERM to stop Minecraft gracefully

- Set up SIGTERM signal trap to invoke stop_server
- Ensure proper process exit and cleanup after the server stops
- Create makefile to build, clean, and install builds

.gitignore

@@ -1,2 +1,3 @@
 data
 .env
+screenlog.0

Dockerfile

@@ -10,7 +10,7 @@ RUN groupadd -g 1000 minecraft && \
 
 # Install scripting dependencies
 RUN apt-get update && \
-    apt-get install -y curl gpg jq screen && \
+    apt-get install -y curl gpg jq procps screen strace && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 

Makefile

@@ -0,0 +1,17 @@
+CONTAINER = minecraft-minecraft-1
+
+.PHONY: default build clean install
+default: build
+
+build:
+	docker compose build
+
+clean:
+	rm -f screenlog.0
+	docker compose down --rmi all
+	docker builder prune -f
+
+install: build
+	touch screenlog.0
+	docker compose up -d && \
+	docker logs -f $(CONTAINER)

README.md

@@ -1,13 +1,24 @@
 # Minecraft Docker Image
 This Dockerfile sets up a Minecraft server based on the `debian-slim` image.
 
+## Quick Start
 By running the following and building this image, you are agreeing to
 [Minecraft's EULA](https://www.minecraft.net/en-us/eula):
 ```
 echo "EULA=true" > .env
 ```
 
-To build and test the image:
+Build the image using the Makefile:
+```
+make build
+```
+
+Optionally, build _and_ run to test it:
+```
+make install
+```
+
+Feel free to use `docker compose` directly to build and test:
 ```
 docker compose build
 docker compose up -d

docker-compose.yml

@@ -1,6 +1,3 @@
-volumes:
-  minecraft:
-
 services:
   minecraft:
     build:
@@ -12,12 +9,10 @@ services:
     image: ${IMAGE:-minecraft}:${TAG:-latest}
     ports:
       - "0.0.0.0:25565:25565"
-    #volumes:
-    #  - minecraft:/app/world
     environment:
       EULA: "${EULA:-false}"
       DEBUG: "${DEBUG:-false}"
-      JVM_OPTS: "-Xms1G -Xmx2G"
+      JVM_OPTS: "${JAVA_OPTS:--Xms1G -Xmx2G}"
       SETTINGS_gamemode: "${GAMEMODE:-survival}"
       SETTINGS_hardcore: "${HARDCORE:-false}"
       SETTINGS_motd: "${MOTD:-A Minecraft Server}"

entrypoint.sh

@@ -1,5 +1,44 @@
 #!/bin/bash
 
+# Check if the minecraft screen is still running
+check_screen() {
+  if [ "$(screen -ls | grep -cE '[0-9]+\.minecraft')" -eq 1 ]; then
+    return 0
+  else
+    return 1
+  fi
+}
+
+# Function to stop the server gracefully
+stop_server() {
+  if check_screen; then
+    # Run 'stop' inside screen and wait for the screen to exit
+    /usr/bin/screen -p 0 -S minecraft -X eval 'stuff "stop"\015'
+    wait "$STRACE_PID"
+
+    # Stop tail -f to stdout
+    if kill -0 "$TAIL_PID" 2>/dev/null; then
+      kill "$TAIL_PID"
+    fi
+
+    # Check only this script is running (PID 1) and pgrep (2 PIDs total)
+    PGREP_OUTPUT="$(pgrep .)"
+    if ! [ "$(echo "$PGREP_OUTPUT" | wc -l)" -eq 2 ]; then
+      echo "[WARN] Some processes might not have exited:"
+      echo "$PGREP_OUTPUT"
+      exit 1
+    fi
+
+    # Exit cleanly
+    echo "[INFO] Server stopped gracefully"
+    exit 0
+  else
+    echo "[ERROR]: Can't find which screen to use"
+    screen -ls
+    exit 1
+  fi
+}
+
 # Enable debug mode
 DEBUG="${DEBUG:-false}"
 if [ "$DEBUG" = "true" ]; then
@@ -32,8 +71,9 @@ while IFS='=' read -r ENVVAR VALUE ; do
       rm "${FILE}.bak"
     fi
   else
-    [ "$DEBUG" = "true" ] && \
+    if [ "$DEBUG" = "true" ]; then
       echo "[DEBUG] \"$ENVVAR\" doesn't have the prefix \"$PREFIX\""
+    fi
   fi
 done < <(env)
 
@@ -43,17 +83,33 @@ if [ "$DEBUG" = "true" ]; then
   cat "$FILE"
 fi
 
-# Pre-create the screen log
-touch screenlog.0
+# Set up a SIGTERM signal trap to stop the server
+trap 'stop_server' SIGTERM
 
 # Run server in screen (without attaching)
+echo "[INFO] Starting Minecraft server"
 /usr/bin/screen -dmS minecraft -L \
-  bash -c "
-    sleep 0.5
-    [ $DEBUG = true ] && echo '[DEBUG] Starting server'
-    /usr/bin/java $JVM_OPTS -jar server.jar --nogui
-  "
+  bash -c "/usr/bin/java $JVM_OPTS -jar server.jar --nogui"
 
-# Tail screen log to container stdout
-[ "$DEBUG" = "true" ] && echo "[DEBUG] Tailing screenlog.0"
-tail -f screenlog.0
+# Get screen PID
+[ "$DEBUG" = "true" ] && screen -ls
+SCREEN_PID="$(
+  screen -ls | grep -oE '[0-9]+\.minecraft' | cut -d. -f1
+)"
+
+# Check screen PID
+if ! kill -0 "$SCREEN_PID" 2>/dev/null; then
+  echo "[ERROR] Cannot find Minecraft screen (PID: \"$SCREEN_PID\")"
+  exit 1
+fi
+
+# Output logs to stdout (touch in case slow to create)
+touch screenlog.0
+tail -f screenlog.0 &
+TAIL_PID="$!"
+
+# Wait for screen to exit
+strace -e exit -e signal=none -p "$SCREEN_PID" 2>/dev/null &
+STRACE_PID="$!"
+[ "$DEBUG" = "true" ] && ps aux
+wait "$STRACE_PID"