Rapid early-ramdisk system initialization, accompanying initramfs generator. CURRENTLY IN DEVELOPMENT

ignited is a simple program meant to run before your Linux system partition has even been mounted! It is intended to run inside your initramfs and bring your system to a usable state, at which point it hands off execution to your /sbin/init program (which could be systemd, initd, or any other init program). More specifically, ignited would be your initramfs' /init.

ignited is also the program used to generate initramfs images that contains the ignited /init and necessary kernel modules.

Although written in Rust, ignited is based on Booster which itself is written in Go. Booster is licensed under MIT.

From Booster's README:

Initramfs is a specially crafted small root filesystem that
[is] mounted at the early stages of Linux OS boot process.
This initramfs, among other things, is responsible for [...]
mounting [the] root filesystem.

In other words, the initramfs is in charge of bringing the system to a usable state, mounting the root filesystem, and handing off further work to your system's init.

ignited only supports Linux systems, and there are no plans to expand compatibility to other OSes.

If any Linux distribution maintainer/developer is exploring the use of ignited inside their initramfs archives (or is already doing so), please contact me to be included in this README. I am also able to give recommendations on proper integration in a distribution if you contact me.

initramfs generation programs generally fall into 2 categories:

• Distro-specific programs such as mkinitcpio.
• Universal, extensible programs such as dracut.

The former is generally tied to a specific Linux distribution (such as Arch Linux) and will not function properly outside of it without modification. The latter eschews specific behaviors in favor of widely-used, mostly distro-agnostic components (such as systemd or busybox). In most cases, neither are specifically designed for boot time performance nor image-generation performance. Neither do they strive to be self-contained.

ignited seeks to fulfill three goals:

• Fast image-generation and boot time.
• Compatibility with as many distributions as possible (including ones without systemd, busybox, or even udevd).
• Contain as close to no external dependencies as possible.

At the time of this writing, not all goals have been fulfilled. See GOALS.md in the git repo for what progress needs to be made.

• dracut doesn't optimize for image-generation speed, as evidenced by this post by Michael Stapelberg in which he recorded ~31s for dracut image generation with gzip (lowered to ~9s with pigz).
• While dracut is compatible with many distributions (such as Fedora/RHEL, Debian, Arch Linux, openSUSE, among others), its upstream default hooks rely on systemd and/or busybox. Theoretically, it seems that special hooks could be made for non-standard configurations, but they don't seem to be explicitly supported.
• While systemd might be statically compiled with musl, such configuration is non-standard and requires various patches. dracut's upstream default hooks also bundle many scripts to be executed at boot time, thus requiring additional files and interpreters (plus its dynamic link and their libraries). Additionally, image-generation consists on running various scripts and binaries to build the image, which may pull in other dependencies.

• Image-generation takes between 10-20 seconds on my AMD Threadripper 3960X with mkinitcpio.
• mkinitcpio is specifically designed for Arch Linux and derivatives.
• Two options are given for initramfs generation by default: udev+busybox, or systemd, both of which come with the same problems as described in Why not dracut?. Additionally, mkinitcpio makes use of hooks (similarly to dracut), therefore inheriting its drawbacks.

ignited is based on booster, therefore inheriting its benefits over other initramfs generators. As time progresses, ignited will differentiate itself from booster with specific features such as verified root, A/B system partitions, and /vendor partition support.

While all code should be properly documented, docs.rs currently doesn't support automatic rustdoc generation for binaries. Work is being done to remedy this and provide proper generated documentation. In the meantime you can browse the source code.

ignited(1) and ignited(8) man pages will be made in the future describing the initramfs' /init behavior and the initramfs generator respectively.

initd is a simple, serviced-compatible init implementation that is perfectly suitable for systems with ignited-generated initramfs. ignited can handoff further execution to initd after the root filesystem has been mounted. You can learn more on initd's git repo. Note that having initd installed is not necessary to use ignited, as it can function just as well if your system uses systemd, runit, dinit, OpenRC, or whatever init program you choose to use.

License: MITNFA