Use the local user's user id in the container when building and running, otherwise bind mounts don't have the correct ownership.

Correct output from steamcmd to avoid red herrings by creating a directory it expects as well as providing a shared object it also expects.
Update docs.

README.md

@@ -31,6 +31,12 @@ git clone https://ceregatti.org/git/daniel/dayzdockerserver.git
 cd dayzdockerserver
 ```
 
+Create a `.env` file that contains your user id. Usually the `${UID}` shell variable has this:
+
+```shell
+echo "export USER_ID=${UID}" | tee .env
+```
+
 Build the Docker images:
 
 ```shell

docker-compose.yml

@@ -19,7 +19,11 @@ volumes:
 services:
 
   web:
-    build: web
+    build:
+      context: web
+      args:
+        - USER_ID
+    user: ${USER_ID}
     volumes:
       - homedir_main:/home/user
       - serverfiles:/serverfiles
@@ -37,7 +41,11 @@ services:
       - .env
 
   server:
-    build: server
+    build:
+      context: server
+      args:
+        - USER_ID
+    user: ${USER_ID}
     volumes:
       - homedir_server:/home/user
       - serverfiles:/serverfiles

server/Dockerfile

@@ -37,8 +37,10 @@ ENV PATH /files/bin:/server:${PATH}
 RUN cd /usr/local && git clone https://github.com/indepth666/py3rcon.git
 
 # Setup a non-privileged user
-RUN groupadd user && \
+ARG USER_ID
-    useradd -l -g user user && \
+
+RUN groupadd -g ${USER_ID} user && \
+    useradd -l -u ${USER_ID} -m -g user user && \
     mkdir -p /home/user /serverfiles/mpmissions /mods /mpmissions /profiles && \
     chown -R user:user /home/user /serverfiles /mods /mpmissions /profiles
 

web/Dockerfile

@@ -61,11 +61,16 @@ ENV PATH      $NVM_DIR/versions/node/v$NODE_VERSION/bin:$PATH
 RUN cd /usr/local && git clone https://github.com/indepth666/py3rcon.git
 
 # Setup a non-privileged user
-RUN groupadd user && \
+ARG USER_ID
-    useradd -l -g user user && \
+
+RUN groupadd -g ${USER_ID} user && \
+    useradd -l -u ${USER_ID} -m -g user user && \
     mkdir -p /home/user /serverfiles/mpmissions /serverfiles/steamapps/workshop/content /web && \
     chown -R user:user /home/user /serverfiles /web
 
+# Shut steamcmd up
+RUN cd /usr/lib/i386-linux-gnu && ln -s /web/bin/steamservice.so
+
 # Add our startup script, as this rarely changes.
 COPY --chown=user:user start.sh /usr/local/bin/start.sh