Add some environment variables

doc/docker.markdown

@@ -69,6 +69,18 @@ You can attach 2 volumes to your container:
 
 Use the flag `-v` to mount a volume on the host machine like described in [official Docker documentation](https://docs.docker.com/engine/userguide/containers/dockervolumes/).
 
+Upgrade your container
+----------------------
+
+- Pull the new image
+- Remove the old container
+- Restart a new container with the same volumes
+
+Environment variables
+---------------------
+
+The list of environment variables is available on [this page](env.markdown).
+
 Config files
 ------------
 

doc/env.markdown

@@ -0,0 +1,11 @@
+Environment Variables
+=====================
+
+Environment variables maybe useful when Kanboard is deployed as container (Docker).
+
+| Variable      | Description                                                                                                                     |
+|---------------|---------------------------------------------------------------------------------------------------------------------------------|
+| DATABASE_URL  | `[database type]://[username]:[password]@[host]:[port]/[database name]`, example: `postgres://foo:foo@myserver:5432/kanboard`   |
+| DEBUG         | Enable/Disable debug mode                                                                                                       |
+| DEBUG_FILE    | Debug file location, `DEBUG_FILE=php://stderr`                                                                                  |
+| ENABLE_SYSLOG | Enable/Disable logging to Syslog: `ENABLE_SYSLOG=1`                                                                             |

doc/index.markdown

@@ -105,6 +105,7 @@ Technical details
 
 - [Daily background job](cronjob.markdown)
 - [Config file](config.markdown)
+- [Environment variables](env.markdown)
 - [Email configuration](email-configuration.markdown)
 - [URL rewriting](nice-urls.markdown)