Created Debugging (markdown)

Debugging.md

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+Even when running your Invoice Ninja setup with Docker - errors can occur. Depending on where the error happens - the webserver, Invoice Ninja or the database - different log files can be responsible. 
+
+## Show logs without `docker-compose`
+
+If you are not running `docker-compose` you first need to find the container id for your php container with `docker ps`. Then you can run
+
+```shell
+docker logs -f <CONTAINER NAME>
+```
+
+This gives you a constant output of the log files for the php container.
+
+## Show logs with `docker-compose`
+
+If you are running the `docker-compose` setup you can output all logs, from all containers, with the following command
+
+```shell
+docker-compose logs -f
+```
+
+If you better want a physical log file in in your `storage/logs` folder, just add `-e LOG=single` to the [usage](#usage) command. 
+Or add an environment variable 
+
+```yml
+...
+environment:
+  LOG: single
+...
+```
+
+to your `docker-compose.yml`.
+
+This generated log file will only hold Invoice Ninja information.