Re: debian init.d scripts
Karsten> S is single user. Same as '1'.
itz> This is not quite right.
itz>
itz> S is the real single-user level. 1 OTOH is used just as a
itz> way-station
Ethan> not quite, S is for script that need to be run once per boot.
Ethan> its run on boot regardless of what runlevel will be entered.
Ethan> things like reading the hardware clock, mounting filesystems
Ethan> and such need not be done on runlevel changes (even multi ->
Ethan> single and back).
itz:~$ ls /etc/rc1.d/
K01wdm K19bind K20ippl K20mysql K20xfs-xtt K90sysklogd
K01xdm K20apache K20logoutd K20queue K21autofs S20single
K11cron K20exim K20lpd K20snort K25ipfw.sh
K12kerneld K20gpm K20makedev K20ssh K83chrony
K14ppp K20inetd K20modclean K20swapd.sh K89atd
itz:~$ cat /etc/rc1.d/S20single
#! /bin/sh
#
# single executed by init(8) upon entering runlevel 1 (single).
#
# Version: @(#)single 1.10 22-Jun-1998 miquels@cistron.nl
#
PATH="/sbin:/bin:/usr/sbin:/usr/bin"
# Kill all processes.
echo -n "Sending all processes the TERM signal... "
killall5 -15
echo "done."
sleep 5
echo -n "Sending all processes the KILL signal... "
killall5 -9
echo "done."
# We start update here, since we just killed it.
update
echo "Entering single-user mode..."
exec init -t1 S
itz:~$
itz> from multiuser to kill all the multiuser services before entering
itz> S with clean slate. If you say "init S" in multiuser you will
itz> end up with a root password prompt because all the getties will
itz> be killed (being under direct control of init), but the services
itz> will stay up.
Ethan> init S == init 1
This is in contradiction to what you say above, apart from also being
factually wrong:
itz:~$ cat /etc/inittab
# /etc/inittab: init(8) configuration.
# $Id: inittab,v 1.8 1998/05/10 10:37:50 miquels Exp $
# The default runlevel.
id:2:initdefault:
# Boot-time system configuration/initialization script.
# This is run first except when booting in emergency (-b) mode.
si::sysinit:/etc/init.d/rcS
# What to do in single-user mode.
>> ~~:S:wait:/sbin/sulogin <<
# /etc/init.d executes the S and K scripts upon change
# of runlevel.
#
# Runlevel 0 is halt.
# Runlevel 1 is single-user.
# Runlevels 2-5 are multi-user.
# Runlevel 6 is reboot.
l0:0:wait:/etc/init.d/rc 0
>> l1:1:wait:/etc/init.d/rc 1 <<
l2:2:wait:/etc/init.d/rc 2
l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4
l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6
# Normally not reached, but fallthrough in case of emergency.
z6:6:respawn:/sbin/sulogin
# What to do when CTRL-ALT-DEL is pressed.
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
# Action on special keypress (ALT-UpArrow).
kb::kbrequest:/bin/echo "Keyboard Request--edit /etc/inittab to let this work."
# What to do when the power fails/returns.
pf::powerwait:/etc/init.d/powerfail start
pn::powerfailnow:/etc/init.d/powerfail now
po::powerokwait:/etc/init.d/powerfail stop
# /sbin/getty invocations for the runlevels.
#
# The "id" field MUST be the same as the last
# characters of the device (after "tty").
#
# Format:
# <id>:<runlevels>:<action>:<process>
#1:2345:respawn:/sbin/getty 38400 tty1
2:2345:respawn:/sbin/mingetty tty2
3:2345:respawn:/sbin/mingetty tty3
4:2345:respawn:/sbin/mingetty tty4
5:2345:respawn:/sbin/mingetty tty5
6:2345:respawn:/sbin/mingetty tty6
#8:2345:respawn:/usr/local/sbin/toproot
# Example how to put a getty on a serial line (for a terminal)
#
#T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100
#T1:23:respawn:/sbin/getty -L ttyS1 9600 vt100
# Example how to put a getty on a modem line.
#
#T3:23:respawn:/sbin/mgetty -x0 -s 57600 ttyS3
itz:~$
itz> If you look at /etc/init.d/rcS (the script that init executes
itz> when entering S) you'll see that _all_ the sub-scripts in
itz> /etc/rcS.d/ are run with "start" as a parameter - which means rcS
itz> _never_ kills anything. If you do "init 1" /etc/init.d/rc is run
itz> instead, which knows how to kill the services by calling
itz> sub-scripts with a "stop" parameter. The last sub-script then
itz> does "init S".
itz>
itz> I don't know why it is done this way; it looks like an ugly hack
itz> to me. I'd just have rcS work the same way as rc (indeed they
itz> should be the same script). Ask me when I am a developer :)
Ethan> its done this way so that its simple to add something to the
Ethan> `must be run at boot once' list of things to do. without it
Ethan> you would have to edit the main initscript /etc/init.d/rc.
Ethan> (which a debian package can't do without violating policy.)
Ethan> the rcS.d is basically the equivilent of redhat's rc.local.
Ethan> redhat has all the `once at boot' stuff crammed into a much
Ethan> more bloated /etc/rc script, which runs rc.local for anything
Ethan> packages or the admin needs added. very messy. rcS.d is far
Ethan> cleaner and simpler.
You didn't get my meaning. I don't object to there being a small rcS
script which run-parts a directory; I object to there being rc _and_
rcS which do the same thing, but are distinct.
--
Ian Zimmerman, Oakland, California, U.S.A.
EngSoc adopts market economy: cheap is wasteful, efficient is expensive.
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