Merge pull request #2075 from gquintard/varnishreload_help

[varnish] varnishreload info

varnish/content.md

@@ -42,7 +42,24 @@ Place this file in the same directory as your `default.vcl`, run `docker build -
 $ docker --tmpfs /var/lib/varnish:exec my-varnish
 ```
 
-### Additional configuration
+## Reloading the configuration
+
+The images all ship with [varnishreload](https://github.com/varnishcache/pkg-varnish-cache/blob/master/systemd/varnishreload#L42) which allows you to easily update the running configuration without restarting the container (and therefore losing your cache). At its most basic, you just need this:
+
+```console
+# update the default.vcl in your container
+docker cp new_default.vcl running_container:/etc/varnish/default.vcl
+# run varnishreload
+docker exec running_container varnishreload
+```
+
+Note that `varnishreload` also supports reloading other files (it doesn't have to be `default.vcl`), labels (`l`), and garbage collection of old labeles (`-m`) among others. To know more, run
+
+```console
+docker run varnish varnishreload -h
+```
+
+## Additional configuration
 
 By default, the containers will use a cache size of 100MB, which is usually a bit too small, but you can quickly set it through the `VARNISH_SIZE` environment variable:
 
@@ -70,7 +87,7 @@ $ docker run %%IMAGE%% varnishd -x parameter
 $ docker run %%IMAGE%% varnishd -a :8080 -b 127.0.0.1:8181 -t 600 -p feature=+http2
 ```
 
-### Exposing the port
+## Exposing the port
 
 ```console
 +$ docker run --name my-running-varnish --tmpfs /var/lib/varnish:exec -d -p 8080:80 my-varnish