Aaron Andersen
373738f3d1
in an initramfs, then transition to the real root filesystem. Useful for systems requiring early boot tasks like LUKS unlock, LVM activation, or network boot before mounting the real root. Adds INIT_CMD_SWITCH_ROOT API command, `initctl switch-root` subcommand, and HOOK_SWITCH_ROOT plugin hook point. The implementation gracefully stops services, moves virtual filesystems (/dev, /proc, /sys, /run) to the new root, deletes initramfs contents to free memory, then execs the new init as PID 1. See GitHub Discussion #292 for background.
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Introduction
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Reverse engineered from the EeePC fastinit
"gaps filled with frog DNA …"
— Claudio Matsuoka
Finit is a process starter and supervisor designed to run as PID 1 on Linux systems. It consists of a set of plugins and can be set up using configuration files. Plugins start at hook points and can run various set up tasks and/or install event handlers that later provide runtime services, e.g., PID file monitoring, or conditions.
Features
- Runlevels, defined per service
- One-shot tasks, services (daemons), or SysV init start/stop scripts
- Runparts and
/etc/rc.localsupport - Process supervision similar to systemd
- Fine-grained privilege control:
- Linux capabilities for minimal required privileges
- Supplementary groups for multi-group resource access
- Sourcing environment files
- Conditions for network/process/custom dependencies
- Readiness notification; PID files (native) for synchronizing system startup, support for systemd sd_notify(), or s6 style too
- Limited support for tmpfiles.d(5) (no aging, attributes, or subvolumes)
- Pre/Post script actions
- Rudimentary templating support
- Tooling to enable/disable services
- Automatic reload of modified configuration files (optional)
- Built-in getty
- Built-in watchdog, with support for hand-over to watchdogd
- Built-in support for Debian/BusyBox
/etc/network/interfaces - Cgroups v2, both configuration and monitoring in
initctl top - Plugin support for customization
- Proper rescue mode with bundled
suloginfor protected maintenance shell - Switch root support for initramfs-to-real-root transitions
- Integration with watchdogd for full system supervision
- Logging to kernel ring buffer before
syslogdhas started, see the recommended sysklogd project for complete logging integration and how to log to the kernel ring buffer from scripts usinglogger
For a more thorough overview, see the Features section.
Tip
See SysV Init Compatibility for help to quickly get going with an existing SysV or BusyBox init setup.
Origin
This project is based on the original finit by Claudio Matsuoka which was reverse engineered from syscalls of the EeePC fastinit.
Finit is developed and maintained by Joachim Wiberg at GitHub. Please file bug reports, clone it, or send pull requests for bug fixes and proposed extensions.