diff --git a/.env.example b/.env.example
new file mode 100644
index 0000000..12fde7d
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,22 @@
+# Copy this file to .env before running Docker Compose:
+#   cp .env.example .env
+
+# Published image to run. Use a different repository or tag if you are testing
+# a fork or a specific release.
+PYMC_REPEATER_IMAGE=pymcdev/pymc-repeater:dev
+# PYMC_REPEATER_IMAGE=yellowcooln/pymc-repeater:dev
+
+# SPI/GPIO access uses the host's numeric group IDs. Check your host with:
+#   getent group gpio
+#   getent group spi
+# Example output:
+#   gpio:x:997:
+#   spi:x:999:
+# Put the third field from each output line below.
+GPIO_GID=986
+SPI_GID=989
+
+# Local build only. These are used by docker-compose.build.yml if you build the
+# image yourself instead of pulling PYMC_REPEATER_IMAGE.
+PUID=15888
+PGID=15888
diff --git a/.gitignore b/.gitignore
index 03a1ce0..3942f65 100644
--- a/.gitignore
+++ b/.gitignore
@@ -51,6 +51,7 @@ htmlcov/
 *~
 
 # Config
+.env
 config.yaml
 config.yaml.backup
 identity.json
diff --git a/README.md b/README.md
index 9c028b2..69e1669 100644
--- a/README.md
+++ b/README.md
@@ -349,7 +349,13 @@ You can now run pyMC Repeater from within a [Docker Container](https://www.docke
 
 Here is what you'll need to do in order to get the container running:
 
-1. Create the bind mount directories and copy the example config into the
+1. Copy the Docker environment example and adjust it for your host if needed.
+
+```bash
+cp .env.example .env
+```
+
+2. Create the bind mount directories and copy the example config into the
    Docker config directory.
 
 ```bash
@@ -357,26 +363,30 @@ mkdir -p ./config ./data
 cp ./config.yaml.example ./config/config.yaml
 ```
 
-2. Run the configuration script and follow the prompts.
+Do not bind mount `./config.yaml` directly. The supported Docker layout mounts
+the whole `./config` directory to `/etc/pymc_repeater`, with the config file at
+`./config/config.yaml`.
+
+3. Run the configuration script and follow the prompts.
 
 ```bash
 sudo bash ./setup-radio-config.sh ./config
 ```
 
-3. Review `./config/config.yaml` before first start. You can preconfigure the
+4. Review `./config/config.yaml` before first start. You can preconfigure the
    radio, location, and web UI password there, or leave first-run setup to the
    web interface.
 
-4. Configure the [docker compose](./docker-compose.yml) to your specific hardware and file paths. Be sure to comment-out or delete lines that aren't required for your hardware. Please note that your hardware devices might be at a different path than those listed in the docker compose file. By default, the compose file pulls the published `pymcdev/pymc-repeater:dev` image. If you need a different image tag or repository, set `PYMC_REPEATER_IMAGE` in a `.env` file.
+5. Configure the [docker compose](./docker-compose.yml) to your specific hardware and file paths. Be sure to comment-out or delete lines that aren't required for your hardware. Please note that your hardware devices might be at a different path than those listed in the docker compose file. By default, the compose file pulls the published `pymcdev/pymc-repeater:dev` image. If you need a different image tag or repository, set `PYMC_REPEATER_IMAGE` in `.env`.
 
-5. Make the bind mount directories writable by the container user. The image
+6. Make the bind mount directories writable by the container user. The image
    runs as UID/GID `15888` by default.
 
 ```bash
 sudo chown -R 15888:15888 ./config ./data
 ```
 
-6. If you are using SPI/GPIO hardware, make sure the `GPIO_GID` and `SPI_GID`
+7. If you are using SPI/GPIO hardware, make sure the `GPIO_GID` and `SPI_GID`
    values match the numeric group IDs on your host. These IDs can vary by OS
    image, so check the host before starting the container. If the values do
    not match your host, put the correct numeric IDs in `.env`.
@@ -393,14 +403,14 @@ gpio:x:997:
 spi:x:999:
 ```
 
-Example `.env`:
+Example `.env` values:
 
 ```bash
 GPIO_GID=997
 SPI_GID=999
 ```
 
-7. Pull and start the container.
+8. Pull and start the container.
 
 ```bash
 docker compose pull
@@ -408,8 +418,11 @@ docker compose up -d
 ```
 
 If you are developing locally and want Docker Compose to build the image from
-this checkout instead, uncomment the `build:` block in `docker-compose.yml` and
-run `docker compose up -d --build`.
+this checkout instead, use the local build override:
+
+```bash
+docker compose -f docker-compose.yml -f docker-compose.build.yml up -d --build
+```
 
 ## Roadmap / Planned Features
 
diff --git a/docker-compose.build.yml b/docker-compose.build.yml
new file mode 100644
index 0000000..8933b8d
--- /dev/null
+++ b/docker-compose.build.yml
@@ -0,0 +1,10 @@
+services:
+  pymc-repeater:
+    build:
+      context: .
+      dockerfile: dockerfile
+      args:
+        PUID: ${PUID:-15888}
+        PGID: ${PGID:-15888}
+        GPIO_GID: ${GPIO_GID:-986}
+        SPI_GID: ${SPI_GID:-989}
diff --git a/docker-compose.yml b/docker-compose.yml
index 78633bd..eda6d96 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,16 +1,6 @@
 services:
   pymc-repeater:
     image: ${PYMC_REPEATER_IMAGE:-pymcdev/pymc-repeater:dev}
-    # Uncomment this block to build from a local checkout instead of pulling
-    # the published Docker image.
-    # build:
-    #   context: .
-    #   dockerfile: dockerfile
-    #   args:
-    #     PUID: ${PUID:-15888}
-    #     PGID: ${PGID:-15888}
-    #     GPIO_GID: ${GPIO_GID:-986}
-    #     SPI_GID: ${SPI_GID:-989}
     container_name: pymc-repeater
     restart: unless-stopped
     ports:
@@ -24,7 +14,7 @@ services:
     # SPI DEVICES PERMISSIONS
     cap_add:
       - SYS_RAWIO
-    # USB DEVICSE PERMISSIONS
+    # USB DEVICE PERMISSIONS
     group_add:
       - "${GPIO_GID:-986}"
       - "${SPI_GID:-989}"
diff --git a/docker-entrypoint.sh b/docker-entrypoint.sh
index 518b1da..eb17104 100644
--- a/docker-entrypoint.sh
+++ b/docker-entrypoint.sh
@@ -18,6 +18,16 @@ print_permission_help() {
     echo "For the default image user, run: sudo chown -R ${RUNTIME_UID}:${RUNTIME_GID} ./config ./data" >&2
 }
 
+fail_bad_config_mount() {
+    echo "Invalid Docker config mount: ${CONFIG_PATH} is a directory, but it must be the config file." >&2
+    echo "This usually happens when ./config.yaml is bind-mounted before that host file exists." >&2
+    echo "Use the supported folder mount instead:" >&2
+    echo "  - ./config:/etc/pymc_repeater" >&2
+    echo "Then place the config at ./config/config.yaml." >&2
+    print_permission_help
+    exit 1
+}
+
 copy_or_die() {
     src="$1"
     dest="$2"
@@ -94,6 +104,10 @@ merge_config_from_example() {
     trap - EXIT HUP INT TERM
 }
 
+if [ -d "${CONFIG_PATH}" ] && [ "$(basename "${CONFIG_PATH}")" = "config.yaml" ]; then
+    fail_bad_config_mount
+fi
+
 if [ ! -f "${EXAMPLE_PATH}" ] && [ -f "${BUNDLED_EXAMPLE_PATH}" ]; then
     if ! cp "${BUNDLED_EXAMPLE_PATH}" "${EXAMPLE_PATH}"; then
         echo "Could not copy bundled example config to ${EXAMPLE_PATH}; using bundled example for config merge only." >&2