https://github.com/superfly/init-snapshot

Fly
https://github.com/superfly/init-snapshot

Last synced: 19 days ago
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Fly

• Host: GitHub
• URL: https://github.com/superfly/init-snapshot
• Owner: superfly
• License: mit
• Created: 2021-02-17T20:32:06.000Z (almost 4 years ago)
• Default Branch: public
• Last Pushed: 2024-04-11T15:09:50.000Z (8 months ago)
• Last Synced: 2024-11-17T08:45:05.780Z (27 days ago)
• Language: Rust
• Size: 33.2 KB
• Stars: 270
• Watchers: 11
• Forks: 25
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
# Fly Init

This is a public snapshot of Fly's init code. It powers every Firecracker microvm we run for our users.

It is Rust-based and we thought making it public (even in this very limited fashion) could help as a reference for people making Rust-based init programs.

## Usage

Please note that our init is tailored for firecracker microvms. These instructions might not quite work and differ from what we do in production.

- Build with `cargo build --release`

- Create a device for the init

```bash

fallocate -l 64M tmpinit

mkfs.ext2 tmpinit

mkdir initmount

mount -o loop,noatime tmpinit initmount

mkdir initmount/fly

cp target/x86_64-unknown-linux-musl/release/init initmount/fly/init

cp run.json initmount/fly/run.json # more on this later

umount initmount

```

- Attach this device as /dev/vda

- Attach your rootfs as /dev/vdb

- Attach a vsock virtio device

### initrd

This init should also work packaged as an initrd. However, we're not running it as such at the time of this writing.

```bash

mkdir -p tmpcpio/fly

cp target/x86_64-unknown-linux-musl/release/init tmpcpio/fly/init

cp run.json tmpcpio/fly/run.json

cd tmpcpio

ls | cpio --null --create -V --format=newc -O ../initrd.cpio

```

You can then use initrd.cpio as your initrd parameter.

## `/fly/run.json`

To configure out init, we're injecting a JSON file into the root device.

You should be able to figure out the format by looking at [`lib.rs`](src/lib.rs)