Firefly Init - MicroVM init

Introduction

This is a tiny init for MicroVMs. It can set hostname, dns, and run a entrypoint command like docker.

Build

This project is built with Taskfile. But you can also build it manually.

Taskfile

task initramfs

Manual Build

mkdir build
cd firefly
export CGO_ENABLED=0
go build -o ../build/init . 

then create initramfs:

mkdir build/initramfs
cp build/init build/initramfs/init
chmod +x build/initramfs/init
find . | cpio -o -H newc > ../initramfs.cpio

Usage

FireFly read commandline arguments from /proc/cmdline:

for example:

root=/dev/vda ip=192.168.10.2/24:192.168.10.1 endpoint=/bin/bash

• root is the root device
• ip is the static ip 192.168.10.2/24 with gateway 192.168.10.1
• endpoint is the entrypoint command

Features

• Set hostname
• Set dns
• Set static ip
• Run entrypoint
• Auto mount necessary filesystems such as /dev, /proc, /sys, etc
• Shutdown VM if entrypoint exits

Supported Commandline Arguments

• hostname is the hostname
• dns is the dns server
• root is the root device
• rootfstype is the root filesystem type, default is ext4
• ip is the static ip
• endpoint is the entrypoint

Rescue Shell

Firefly can run a rescue shell if something goes wrong. Such as cannot found root device, entrypoint not found...

You can add shell binary to /bin/sh, or run task build-busybox to add busybox to rootfs.

License

MIT