docs: add riklet documentation

Signed-off-by: Malo Polese <malo.polese@gmail.com>

docs/src/reference/riklet.md

@@ -0,0 +1,41 @@
+# Riklet
+
+[Rust in Kube (RIK)](https://github.com/dev-sys-do/rik) node agent
+
+## Faas Configuration
+
+**Prerequisite**: You need firecracker in yout PATH.
+
+Here is a list of **required** environment variables to run riklet:
+
+| Environment Variable   | Description                                                                                                             | Default |
+| ---------------------- | ----------------------------------------------------------------------------------------------------------------------- | ------- |
+| `IFACE`                | Network interface connected to the internet                                                                             | ""      |
+| `IFACE_IP`             | IP of the Network interface connected to the internet                                                                   | ""      |
+| `FIRECRACKER_LOCATION` | Path to the firecracker binary                                                                                          | ""      |
+| `KERNEL_LOCATION`      | Path to the kernel location                                                                                             | ""      |
+| `SCRIPT_LOCATION`      | Path to the [script](https://github.com/polyxia-org/rik/blob/main/scripts/setup-host-tap.sh) that create tap interface. | ""      |
+
+To run riklet with FAAS configuration.
+
+```bash
+sudo riklet --kernel-path ${KERNEL_LOCATION} \
+            --ifnet ${IFACE} \
+            --ifnet-ip ${IFACE_IP} \
+            --script-path ${SCRIPT_LOCATION}
+```
+
+> The firecracker binary location is determined by the following order:
+>
+> - **$FIRECRACKER_LOCATION** environment variable: direct path to the binary
+> - **$PATH** environment variable: search for the binary in the directories
+> - firecracker binary in the current working directory
+
+Exemple:
+
+```bash
+sudo riklet --kernel-path ./vmlinux.bin  \
+            --ifnet wlp2s0  \
+            --ifnet-ip 192.168.1.84  \
+            --script-path ./scripts/setup-host-tap.sh
+```