s6-linux-init

What is it ?

s6-linux-init is a set of minimalistic tools used to create a s6-based init system, including a /sbin/init binary, on a Linux kernel. It is a part of the s6 ecosystem.

The resulting architecture follows the Unix philosophy (one job → one tool) as closely as possible, and is fully dedicated to the s6 way of managing a system:

s6-svscan runs as process 1 for the whole machine lifetime.
Every daemon is supervised.
No logs are ever lost.
Policy is entirely left to the user. Typically, any service manager can be run on top of s6-linux-init.

Nevertheless, the architecture is fully compliant with various empirical and historical specifications. For instance, it provides:

utmp management compatible with sysvinit
runlevel management, with a configurable default, overridable from the kernel command line
sysvinit-like commands to shut the system down, including a shutdown command that follows the LSB specification

Why s6-linux-init ?
An overview of s6-linux-init
A quickstart guide for the impatient, along with a FAQ

Installation

Requirements

A Linux-based system with a standard C development environment
GNU make, version 3.81 or later
skalibs version 2.11.2.0 or later. It's a build-time requirement. It's also a run-time requirement (for s6-linux-init-maker) as well as a boot-time requirement (i.e. a run-time requirement for the programs used when you boot a system created with s6-linux-init-maker) if you link against the shared version of the skalibs library.
execline version 2.8.3.0 or later. It is a build-time and boot-time requirement.
s6 version 2.11.1.0 or later. It is a build-time and boot-time requirement.

The following optional dependencies are also supported:

If you're using musl and want nsswitch-like functionality: nsss version 0.2.0.1 or later (build-time and boot-time)
If you want secure utmp functionality: utmps version 0.1.1.0 or later (build-time and boot-time)

All those dependencies are build-time and run-time, except possibly skalibs, which is not needed at run time if you are linking all the other packages against the static version of libskarnet.

Licensing

s6-linux-init is free software. It is available under the ISC license.

Download

The current released version of s6-linux-init is 1.0.7.3.
Alternatively, you can checkout a copy of the s6-linux-init git repository:
```
 git clone git://git.skarnet.org/s6-linux-init 
```
There's also a GitHub mirror of the s6-linux-init git repository.

Compilation

See the enclosed INSTALL file for installation details.

Upgrade notes

This page lists the differences to be aware of between the previous versions of s6-linux-init and the current one.

Reference

General

A rationale for this package
An overview of s6-linux-init
A quickstart page

Commands

Unless more details are provided in an Exit codes section of a specific page, all these commands exit 0 on success, 111 if they encounter a temporary error (such as a system call failure) and 100 if they encounter a permanent error (such as a misuse).

Related resources

s6-linux-init is discussed on the skaware and supervision mailing-lists.
There is a #s6 IRC channel on OFTC. Sometimes people are there and even answer questions.