update base java version to 25, make dependencies explicit, and document container upgrade process

Dockerfile

@@ -8,13 +8,19 @@ RUN unzip -j /usr/bin/mcrcon.zip -d /usr/bin/mc-rcon && chmod a+x /usr/bin/mc-rc
 
 
 # actual image
-FROM eclipse-temurin:21
+FROM eclipse-temurin:25
+
+# included in case the base image doesn't include wget (known bug 08/2026)
+RUN apt-get update && apt-get install -y wget ca-certificates
 
 COPY --from=builder /usr/bin/mc-rcon /usr/bin/mc-rcon
+
 COPY scripts/start-server.sh /usr/bin/start-server.sh
 RUN chmod a+x /usr/bin/start-server.sh
+
 COPY scripts/mcrcon /usr/bin/mcrcon
 RUN chmod a+x /usr/bin/mcrcon
+
 COPY template/ /defaults/
 
 WORKDIR /minecraft_data

README.md

@@ -16,7 +16,7 @@ git clone https://gitea.jovan04.com/evan/minecraft-docker && cd minecraft-docker
 
 ### Build the Image
 ```sh
-docker build -t minecraft_server .
+docker build --pull -t minecraft_server .
 ```
 
 ### Run with Docker Compose
@@ -36,7 +36,29 @@ On first startup (when the data volume is empty):
 * A default RCON configuration is written
 * `server.jar` is downloaded from a provided link
 
-On subsequent startups, existing files are reused unchanged and environment variables are unused.
+On subsequent startups, existing files are reused unchanged and environment variables are unused. To reset the server or create a new one, change the name in `volumes:  data:  name:  new_volume_name` in the `docker-compose.yml` file. 
+
+### Upgrading Java Version
+Occasionally, Minecraft will update the Java version they compile their class files with. Because the Java runtime is pre-bundled with the Docker container, an update from Minecraft requires an update and rebuild of the Docker container. 
+
+You can tell this is required if there are errors like the following when trying to start the server:
+```
+minecraft_server  | Error: LinkageError occurred while loading main class net.minecraft.bundler.Main
+minecraft_server  | 	java.lang.UnsupportedClassVersionError: net/minecraft/bundler/Main has been compiled by a more recent version of the Java Runtime (class file version 69.0), this version of the Java Runtime only recognizes class file versions up to 65.0
+minecraft_server exited with code 1 (restarting)
+```
+
+To upgrade, change the base eclipse-temurin image's version to one supported by the latest Minecraft version. In `./Dockerfile`:
+```
+# previously, eclipse-temurin:21
+FROM eclipse-temurin:25
+```
+
+Then, rebuild the container and start as normal:
+```sh
+docker build --pull -t minecraft_server .
+docker compose up -d
+```
 
 ### RCON Access
 Minecraft implements the Remote Console (RCON) protocol, which allows server administrators to remotely execute commands. See more info [here](https://minecraft.wiki/w/RCON) and [here](https://developer.valvesoftware.com/wiki/Source_RCON_Protocol). RCON access is enabled automatically from inside the container only. **Do not expose the RCON service to the internet directly!!!** RCON is not encrypted, so exposing this service can give hackers direct access to your server's administrator console.

scripts/start-server.sh

@@ -7,7 +7,7 @@ if ! test -f /minecraft_data/server.jar; then
         echo "ERROR: SERVER_JAR_DOWNLOAD_URL not set for initial volume creation"
         exit 1
     fi
-    wget -O /minecraft_data/server.jar "${SERVER_JAR_DOWNLOAD_URL}"
+    wget --no-verbose -O /minecraft_data/server.jar "${SERVER_JAR_DOWNLOAD_URL}"
 fi
 
 # server.properties