doc: document initramfs builder tool

Signed-off-by: Nils Ponsard <[email protected]>

initramfs/src/httpclient.rs

@@ -1,6 +1,7 @@
 use anyhow::{anyhow, Result};
 use reqwest::{Client, Response};
 
+/// Wrapper around reqwest to run a GET request with bearer auth
 pub async fn run_get_request(url: &str, token: Option<&str>) -> Result<Response> {
     let res = match token {
         Some(token) => Client::new().get(url).bearer_auth(token),

initramfs/src/image.rs

@@ -40,6 +40,7 @@ pub struct Layer {
     pub content: Cursor<Bytes>,
 }
 
+/// Represents a container image
 pub struct Image {
     name: String,
     tag: String,

initramfs/src/main.rs

@@ -1,3 +1,14 @@
+//! This is a tool to transform a container image into an initramfs image.
+//! It will download the image from a container registry, extract it and
+//! write it to disk.
+//! The initramfs image will contain the init binary/script and the agent 
+//! binary as well as the agent configuration file.
+//! The init binary will be the entrypoint of the initramfs image and will
+//! start the agent binary.
+//!
+//! This image can then be used as an initramfs image for a linux kernel
+//! in the lambdo runtime.
+
 use std::fs::File;
 
 use anyhow::anyhow;

initramfs/src/registry.rs

@@ -20,6 +20,7 @@ struct ManifestResponse {
     fsLayers: Vec<LayerMetadata>,
 }
 
+/// A container registry (e.g. docker hub)
 pub struct Registry {
     url: String,
     auth_url: String,