Building initramfs

Requirements:

• Rust toolchain (opens in a new tab)

Introduction

Lambdo uses custom initramfs built from Docker images. You can build it by yourself or use prebuilt one.

Lambdo initramfs structure

Lambdo initramfs contains at least 3 components:

• init - init process which starts all other processes.
• agent - agent process which is responsible for communication with Lambdo API.
• config.yaml - configuration file which contains all necessary configuration for Lambdo agent (see Configuration documentation).

Preparation

Create an empty directory for initramfs:

mkdir initramfs

Clone lambdo repository:

git clone https://github.com/faast-rt/lambdo.git

Build Lambdo agent

Build Lambdo agent and move it to initramfs directory:

cd lambdo/agent
cargo build --release
cd ../..
mv lambdo/target/release/agent initramfs

Write init script

You can write your own script or use example one (must be named init):

#! /bin/sh
mount -t devtmpfs dev /dev
mount -t proc proc /proc
mount -t sysfs sysfs /sys
ip link set up dev lo
 
exec /agent --config /config.yaml
 
exit
poweroff -f

Write configuration file

You can write your own configuration file or use example one (must be named config.yaml):

apiVersion: lambdo.io/v1alpha1
kind: AgentConfig
# Leave empty if you want to use default Lambdo API.
grpc:
  remote_port: 50051
  remote_host: 127.0.0.1
  local_port: 0
  local_host: 0.0.0.0

Build initramfs by yourself

Build initramfs tool and move it to initramfs directory:

cd lambdo/initramfs
cargo build --release
cd ../..
mv lambdo/target/release/initramfs initramfs

Run initramfs tool (replace node:20-alpine with the image of the language you want):

cd initramfs
./initramfs --image node:20-alpine

The image built here is stored at initramfs/initramfs-library-node-20-alpine.img.