1  Useful concepts

	1.1  System initialisation
		1.1.1  Chainloading
		1.1.2  Requirements and properties of PID 1
			1.1.2.1  Functional requirements: longruns and oneshots
			1.1.2.2  Signal handling
			1.1.2.3  exit() and exec()
		1.1.3  Aside: history of init [init-hist]

	1.2  Process supervision
		1.2.1  Requirements [s6-ov]
			1.2.1.1  Auto restart
			1.2.1.2  Be itself supervised
				# The need to be rooted in PID 1
			1.2.1.3  Reproducable environment
				# More of a consequence rather than a requirement
		1.2.2  Main choices
			1.2.2.1  No supervision, or with PID files, or with
			         /etc/inittab and /etc/ttys
			1.2.2.2  monit and supervisord; upstart and systemd
			1.2.2.3  daemontools(-encore), runit, perp, s6 and nosh
		1.2.3  Aside: the supervision mail list [sv-ml]

	1.3  Notification without running a service [ftrig]

2  Anatomy of s6 / s6-rc

	2.1  Process supervisior: s6-supervise and s6-svscan
		2.1.1  Configuration and runtime control [s6-ov]
		2.1.2  Readiness notification
		2.1.3  Chainloading and execline

	2.2  Service manager: s6-rc
		2.2.1  Interfaces provided by s6-rc
		2.2.2  Service directory deployment
		2.2.3  Why no OR dependencies for now [or-dep]
			# Compare with "opportunist dependencies"

	2.3  Service logging
		2.3.1  s6-svscan as init: the fd-holding black magic [magic]
		2.3.2  s6-fdholder
			# Restart of s6-fdholder [fh-restart]
		2.3.3  s6-log and ucspilogd
			# /dev/log: SOCK_STREAM and SOCK_DGRAM [log-dgram]
		2.3.4  The good parts of "socket activation" [s6-sa]

	2.4  The DJB legacy and the Plan 9 spirit [djb]
		2.4.1  File system as the channel
		2.4.2  library organisation, eg. buffer.h <-> bio.h
		2.4.3  A glance at the source code

3  A simplified example of s6 / s6-rc deployment

	3.1  s6-linux-init and "refined" phases of init
		# Platform-dependency of stage 1
	3.2  "Runlevel" emulation with s6-rc
	3.3  `emptyenv -p' with setproctitle; `./nosetsid' with dcron
	3.4  Shuffling of fd in ucspilogd's `./run'
	3.5  Coarseness of logging setup in the example
	3.6  Instanced supervision
		# A hybrid of execline and shell? [el-hybrid]
	3.7  Aside: comparison of init scripts [run-comp]

--

[djb] <http://skarnet.org/software/skalibs/djblegacy.html>
[el-hybrid] <http://skarnet.org/cgi-bin/archive.cgi?
                    2:msp:1131:jgoekjpfpjmfnefbkcob>
[fh-restart] <http://skarnet.org/cgi-bin/archive.cgi?
                     2:mss:1107:klkgaflanpnghddcjfej>
[ftrig] <http://skarnet.org/software/s6/ftrig.html>
[init-hist] <http://blog.darknedgy.net/technology/2015/09/05/0/>
            <http://arxiv.org/pdf/0706.2748v2.pdf>
[log-dgram] <http://www.openwall.com/lists/musl/2015/08/10/1>
[magic] <http://skarnet.org/software/s6/s6-svscan-1.html#log>
[run-comp] <http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/
                   run-scripts-and-service-units-side-by-side.html>
[or-dep] <http://skarnet.org/cgi-bin/archive.cgi?
                 2:msp:1063:blhpkmcfbdgbjkmbbckm>
[s6-sa] <http://skarnet.org/software/s6/socket-activation.html>
[s6-ov] <http://skarnet.org/software/s6/overview.html>
[sv-ml] <http://skarnet.org/lists.html>