Add steps to migrate from docker-compose.yml to Toolkit (#226)

* Add steps to migrate from docker-compose.yml to Toolkit

doc/README.md

@@ -11,6 +11,7 @@ documentation on the [Overleaf Wiki](https://github.com/overleaf/overleaf/wiki)
 - [Overview](./overview.md)
 - [Quick Start Guide](./quick-start-guide.md)
 - [Dependencies](./dependencies.md)
+- [docker-compose.yml to Toolkit migration](./docker-compose-to-toolkit-migration.md)
 
 
 ## Using the Toolkit

doc/docker-compose-to-toolkit-migration.md

@@ -0,0 +1,86 @@
+# docker-compose.yml to Toolkit migration #
+
+If you're currently using Docker Compose via a `docker-compose.yml` file, migrating to the Toolkit can make running an on-premises version of Overleaf easier to deploy, upgrade and maintain.
+
+To migrate, you'll need to convert your existing Docker Compose setup into the format used by the Toolkit. This process involves copying existing configuration into the Toolkit.
+
+This guide will walk you through each step of this process, ensuring a smooth migration from Docker Compose to the Toolkit.
+
+**Note:** These instructions are for v4.x and earlier. Therefore all variables use the `SHARELATEX_` prefix instead of `OVERLEAF_`
+
+## Clone the Toolkit repository ##
+
+First, let's clone this Toolkit repository to the host machine:
+```
+$ git clone https://github.com/overleaf/toolkit.git ./overleaf-toolkit
+```
+Next run the `bin/init` command to initialise the Toolkit with its default configuration.
+
+## Setting the image and version ##
+
+In the `docker-compose.yml` file the image and version are defined in the component description:
+
+```
+version: '2.2'
+services:
+    sharelatex:
+        restart: always
+        # Server Pro users:
+        # image: quay.io/sharelatex/sharelatex-pro
+        image: sharelatex/sharelatex:3.5.13
+```
+
+When using the Toolkit, the image name is automatically resolved; the only requirement is to set `SERVER_PRO=true` in **config/overleaf.rc** to pick the Server Pro image or `SERVER_PRO=false` to use Community Edition.
+
+The desired Server Pro/Community Edition version number is set in the **config/version** file. The Toolkit requires a specific version number like "**4.2.3**". In case you are using `latest`, you can use `bin/images` to find the image id of your local `latest` version, then use the release notes for [2.x](https://github.com/overleaf/overleaf/wiki/Release-Notes-2.0), [3.x](https://github.com/overleaf/overleaf/wiki/Release-Notes-3.x.x), [4.x](https://github.com/overleaf/overleaf/wiki/Release-Notes--4.x.x) or [5.x](https://github.com/overleaf/overleaf/wiki/Release-Notes-5.x.x) to map the image id to the version.
+
+If you are sourcing the image from your own internal registry you can override the image the Toolkit uses by setting `SHARELATEX_IMAGE_NAME`. You do not need to specify the tag as the Toolkit will automatically add it based on your **config/version** file.
+
+## Configuring external access ##
+
+By default, Overleaf will listen on **127.0.0.1:80**, only allowing traffic from the Docker host machine.
+
+To allow external access, you’ll need to set the `SHARELATEX_LISTEN_IP` and `SHARELATEX_PORT` in the **config/overleaf.rc** file.
+
+## Environment variable migration ##
+
+You’ll likely have a set of environment variables defined in the **sharelatex** service:
+
+```
+environment:
+    SHARELATEX_APP_NAME: Overleaf Community Edition
+    SHARELATEX_PROXY_LEARN: 'true'
+    …
+```
+
+Each of these variables should be copied, with several exceptions we’ll list later, into the Toolkit’s **config/variables.env** file, ensuring the following form (note the use of `=` instead of `:`):
+
+```
+SHARELATEX_APP_NAME=Overleaf Community Edition
+SHARELATEX_PROXY_LEARN=true
+```
+
+As mentioned above, there are several exceptions, as certain features are configured differently when using the Toolkit:
+
+- Variables starting with `SANDBOXED_COMPILES_` and `DOCKER_RUNNER` are no longer needed. To enable [Sandboxed Compiles](./sandboxed-compiles.md), set `SIBLING_CONTAINERS_ENABLED=true` in your **config/overleaf.rc** file.
+- Variables starting with `SHARELATEX_MONGO_`, `SHARELATEX_REDIS_` and the `REDIS_HOST` variable are no longer needed. MongoDB and Redis are now configured in the **config/overleaf.rc** file using  `MONGO_URL`, `REDIS_HOST` and `REDIS_PORT`.
+
+For advanced configuration options, refer to the [overleaf.rc](./overleaf-rc.md) documentation.
+
+## NGINX Proxy ##
+
+For instructions on how to migrate `nginx`, please see [TLS Proxy for Overleaf Toolkit environment](tls-proxy.md)
+
+## Volumes ##
+
+### ShareLaTeX ###
+
+The location of the data volume for the `sharelatex` container will need to be set using `OVERLEAF_DATA_PATH` in the **config/overleaf.rc** file.
+
+### MongoDB ###
+
+The location of the data volume for the `mongo` container will need to be set using `MONGO_DATA_PATH` in the **config/overleaf.rc** file.
+
+### Redis ###
+
+The location of the data volume for the `redis` container will need to be set using `REDIS_DATA_PATH` in the **config/overleaf.rc** file.