Update mattermost

mattermost/README.md

@@ -130,6 +130,22 @@ docker-compose up -d
 
 Your Docker image should now be on the latest Mattermost version.
 
+
+## Upgrading Mattermost to 4.9+
+
+Docker images for `4.9.0` release introduce some important changes from [PR #241](https://github.com/mattermost/mattermost-docker/pull/241) to improve production use of Mattermost with Docker.
+**There are 2 important changes for existing installations**  
+
+One important change is that we don't use `root` user by default to run the Mattermost application. So, as explained on [the README](https://github.com/mattermost/mattermost-docker#start), if you use host mounted volume you have to be sure that files on your host server have the correct UID/GID (by default those values are `2000`). In practice, you should just run following commands :
+```
+mkdir -p ./volumes/app/mattermost/{data,logs,config}
+chown -R 2000:2000 ./volumes/app/mattermost/
+```
+
+The second important change is the port used by Mattermost application container. The default port is now `8000`, and existing installations that use port `80` will not work without a little configuration change. You have to open your Mattermost configuration file (`./volumes/app/mattermost/config/config.json` by default) and change the key `ServiceSettings.ListenAddress` to `:8000`.  
+Also if you use your own web-server/reverse-proxy you need to change its configuration to reach port `8000` of the Mattermost container.
+
+
 ## Upgrading to Team Edition 3.0.x from 2.x
 
 You need to migrate your database before upgrading Mattermost to `3.0.x` from

mattermost/app/Dockerfile

@@ -2,7 +2,7 @@ FROM alpine:3.6
 
 # Some ENV variables
 ENV PATH="/mattermost/bin:${PATH}"
-ENV MM_VERSION=4.9.0
+ENV MM_VERSION=4.9.1
 
 # Build argument to set Mattermost edition
 ARG edition=enterprise