From 55806162353d27e371b85ef9155e2330598fdb87 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Thu, 7 Mar 2019 07:35:14 +0000
Subject: [PATCH] Document the `generate` option for the docker image.

---
 changelog.d/4824.misc |  1 +
 docker/README.md      | 41 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 38 insertions(+), 4 deletions(-)
 create mode 100644 changelog.d/4824.misc

diff --git a/changelog.d/4824.misc b/changelog.d/4824.misc
new file mode 100644
index 000000000..a4c5a1df3
--- /dev/null
+++ b/changelog.d/4824.misc
@@ -0,0 +1 @@
+Document the `generate` option for the docker image.
diff --git a/docker/README.md b/docker/README.md
index 3faedf629..4b98b7fd7 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -28,7 +28,7 @@ with your postgres database.
 docker run \
     -d \
     --name synapse \
-    -v ${DATA_PATH}:/data \
+    --mount type=volume,src=synapse-data,dst=/data \
     -e SYNAPSE_SERVER_NAME=my.matrix.host \
     -e SYNAPSE_REPORT_STATS=yes \
     matrixdotorg/synapse:latest
@@ -87,10 +87,15 @@ Global settings:
 * ``SYNAPSE_CONFIG_PATH``, path to a custom config file
 
 If ``SYNAPSE_CONFIG_PATH`` is set, you should generate a configuration file
-then customize it manually. No other environment variable is required.
+then customize it manually: see [Generating a config
+file](#generating-a-config-file).
 
-Otherwise, a dynamic configuration file will be used. The following environment
-variables are available for configuration:
+Otherwise, a dynamic configuration file will be used.
+
+### Environment variables used to build a dynamic configuration file
+
+The following environment variables are used to build the configuration file
+when ``SYNAPSE_CONFIG_PATH`` is not set.
 
 * ``SYNAPSE_SERVER_NAME`` (mandatory), the server public hostname.
 * ``SYNAPSE_REPORT_STATS``, (mandatory, ``yes`` or ``no``), enable anonymous
@@ -143,3 +148,31 @@ Mail server specific values (will not send emails if not set):
   any.
 * ``SYNAPSE_SMTP_PASSWORD``, password for authenticating against the mail
   server if any.
+
+### Generating a config file
+
+It is possible to generate a basic configuration file for use with
+`SYNAPSE_CONFIG_PATH` using the `generate` commandline option. You will need to
+specify values for `SYNAPSE_CONFIG_PATH`, `SYNAPSE_SERVER_NAME` and
+`SYNAPSE_REPORT_STATS`, and mount a docker volume to store the data on. For
+example:
+
+```
+docker run -it --rm
+    --mount type=volume,src=synapse-data,dst=/data \
+    -e SYNAPSE_CONFIG_PATH=/data/homeserver.yaml \
+    -e SYNAPSE_SERVER_NAME=my.matrix.host \
+    -e SYNAPSE_REPORT_STATS=yes \
+    matrixdotorg/synapse:latest generate
+```
+
+This will generate a `homeserver.yaml` in (typically)
+`/var/lib/docker/volumes/synapse-data/_data`, which you can then customise and
+use with:
+
+```
+docker run -d --name synapse \
+    --mount type=volume,src=synapse-data,dst=/data \
+    -e SYNAPSE_CONFIG_PATH=/data/homeserver.yaml \
+    matrixdotorg/synapse:latest
+```