Update README.md

BACK/README.md

@@ -1,4 +1,69 @@
 # Backend
-BACK contains two backend applications for deploying and managing tenants. The frontend APP uses these backends to enter "SuperAdmin" mode, it can communicate seamlessly with either of them. 
+BACK contains a backend application for deploying and managing tenants. The frontend APP uses this backend to enter "SuperAdmin" mode. The backend has two modes of operation: docker or kubernetes. 
 
-Docker Backend uses docker compose to launch a tenant while Kube Backend uses kubernetes, creating a new namespace for each tenant. 
+The docker mode that connects to a local instance of docker to create new tenants. A new tenant consists of a docker compose deployment of up to 4 containers: API, DB, WebApp and Swagger Doc. Once the frontend connects to this backend, it changes its interface to SuperAdmin mode.  
+
+The kubernetes mode works in a quite similar way, connecting to a kubernetes cluster and creating namespaces for each new tenant.
+
+## Building with Docker
+No Go installed? No problem, docker got you covered! Run the following command to build the backend binary, according to your OS:
+```console
+# Windows 
+docker run --rm -v ${PWD}:/workdir -w /workdir -e GOOS=windows golang go build -o ogree_app_backend.exe
+# Linux 
+docker run --rm -v $(pwd):/workdir -w /workdir -e GOOS=linux golang go build -o ogree_app_backend
+# MacOS 
+docker run --rm -v $(pwd):/workdir -w /workdir -e GOOS=darwin golang go build -o ogree_app_backend
+```
+
+## Building with Go
+To build it, you should have Go installed (version >= 1.20). To run it, first docker should be up and running.
+
+In the backend directory, run the following to install dependecies:
+```console
+go mod download
+```
+
+Then, to compile and run:
+```console
+go build -o ogree_app_backend
+./ogree_app_backend
+```
+
+## Configuring
+It is mandatory to have the `deploy` folder of OGrEE-Core to properly run the backend. A .env file should also be present under `ogree_app_backend/` with the following format:
+```
+TOKEN_SECRET=yoursecretstring
+TOKEN_HOUR_LIFESPAN=1
+ADM_PASSWORD=adminHashedPassword
+DEPLOY_DIR=../../deploy/
+```
+
+Only one user (admin) can login to the superadmin backend with the password that should be added *hashed* to the .env file. If DEPLOY_DIR is omitted, the default as given in the example will be set. Example of hashed password that translates to `Ogree@148`:
+```
+ADM_PASSWORD="\$2a\$10\$YlOHvFzIBKzfgSxLLQkT0.7PeMsMGv/LhlL0FzDS63XKIZCCDRvim"
+```
+
+A default .env is provided in the repo with the password above.
+
+## Running
+For docker mode, since the backend connects to docker to launch containers, it has to be run **locally**. To choose in what port the backend should run (default port is 8082):
+```
+./ogree_app_backend -port 8083
+```
+
+To use kubernetes mode instead, simply add the kube flag:
+```
+./ogree_app_backend -kube
+```
+
+## Cross compile
+To cross compile from Linux or Mac (that is, compile to a different OS than the one in use), use the commands bellow. For Windows, user `set` for GOOS and GOARCH before running the go build command.
+```console
+# Linux 64-bit
+GOOS=linux GOARCH=amd64 go build -o ogree_app_backend_linux
+# Windows 64-bit
+GOOS=windows GOARCH=amd64 go build -o ogree_app_backend_win
+# MacOS 64-bit
+GOOS=darwin GOARCH=amd64 go build -o ogree_app_backend_mac
+```