Add README Descriptions

- Network Settings
- SSH Public Key
- Networing ports requried
- ssh is not required to access linien-server

README.md

@@ -1,4 +1,10 @@
 # Firmware for the Sinara 8462 Fast-Servo
+## Networking Ports
+| Usage         | Port Number |
+|---------------|-------------|
+| ssh           | 3030        |
+| linien-server | 18862       |
+
 ## Building
 ### Reproducible build with Nix
 1. Run `nix build .#packages.armv7l-linux.fast-servo-sd-image` to build the sd card image.
@@ -10,13 +16,36 @@
 3. Run `sudo dd if=<path to the SD Card Image> of=/dev/<SD Card Device Name in lsblk> bs=4M status=progress oflag=sync`
 4. Eject the SD Card before removal
 
-### Usage
+## Configuration
+You can modify the followings by altering the files directly on the SD card. You can do that by inserting the SD card to a computer in Linux Operating system.
+
+1. Network Settings
+- File Location: /etc/ip_setup
+- Description: It contains the network setup script that is run once during initialization. You can add any network related to scripts to this file.
+
+2. SSH Public Key
+- File Location: /etc/ssh/authorized_keys.d/root
+- Description: SSH Public key authentication file.
+
+You should append the ssh public key of your PC here with hostname removed.
+- Instructions:
+    1. Run `ssh-keygen`
+    2. Type a filename for key to be saved. Let's say `foo`.
+    3. Type `Return(Enter)` twice when it asks for your passphrase. Fast-servo's ssh authentication is passwordless.
+    4. Open the generated public key file `foo.pub`.
+    5. Append the public key to the file `/etc/ssh/authorized_keys.d/root` with `@hostname` removed. 
+        Sample ssh public key: `ssh-ed25519 xxx...xxx username@hostname`
+
+## Usage
 1. Make sure the onboard DIP Switch is in the following condition.
     - EN: OFF
     - MODE: ON
 2. Install the SD Card, power up the board via the power jack or PoE and plug in the RJ45 Ethernet cable.
 3. Wait for all the front panel LEDs except the termination status LEDs to turn off. It can take a minutes or two for first boot. If it does not boot up, try to flash the SD Card again.
-4. By default, linien-server starts up automatically. In case linien-server crashes, it will restart itself. Logs are stored in `/root/linien-server-log`. Here are some commands to interact with the linien-server service once you `ssh <fast servo ip address> -p 3030` into fast-servo.
+4. By default, linien-server starts up automatically. In case linien-server crashes, it will restart itself. Logs are stored in `/root/linien-server-log`. 
+ssh access is not required for linien client if linien-server is started. If not, then linien client will ssh into the fast-servo device to start the linien-server service.
+
+    Here are some commands to interact with the linien-server service once you `ssh <fast servo ip address> -p 3030` into fast-servo. 
 
 | Description                                          | Command                                 |
 |------------------------------------------------------|-----------------------------------------|