BSD/Slackware style init

一篇讲解如何在LFS中使用BSD初始化风格，一般linux发行版中都是使用
SysV初始化风格，如RedHat,Mandrake,LFS...etc. Slackware使用BSD风格。
Debian也有自己的初始化风格，感觉有点象BSD. :)
这篇文章应该会让你了解BSD初始化风格的思想，对从加载内核到login之间
系统如何初始化也会有所了解，虽然是LFS的，但其他发行版初始化系统也都大致相同。
也正因为是LFS的，所以比较简洁明了(看MDK的rc.sysinit有点头晕javascript:window.open(this.src);" style="CURSOR: pointer" onload="return imgzoom(this,550)"> )

Setting up LFS with BSD/Slackware style init

AUTHOR: Leslie Polzer 
AUTHOR: Marc Heerdink 

DATE: 2005-01-08

LICENSE: GNU Free Documentation License Version 1.2

SYNOPSIS: Setting up LFS with BSD/Slackware style init.

DESCRIPTION:
The BSD style is often perceived as a more simple (in contrast to SysVInit) way
of booting your system and controlling runlevels.

PREREQUISITES:
LFS 2.4 or higher.

HINT:

Contents
--------
1 Preface
2 Preparations
2.1 Runlevel planning
2.2 Directory layout
2.3 Setting up /etc/inittab
3 Creating the boot scripts
3.1 Creating essential scripts
3.2 Creating extra scripts
4 Final words


1 Preface
=========

   Since LFS uses SYSV init scripts by default, about everybody who has an LFS
 system uses this kind of init. But a few days ago, I read about someone on the
 mailing list who wanted to setup BSD style init. Since I was using this since
 the beginning i decided to write a hint for everybody who wants to use BSD
 style init (or just wants to try it).

   BSD init uses the normal SYSV init program, but a different inittab and has
 the boot scripts arranged different. BSD boots your system in a much less
 complicated way, so the scripts are easier to maintain. I think one should
 read this hint before installing either init, because the decision should
 preferably be made before the first boot.

   This hint will never be complete, comments can be sent to
 me .


2 Preparations
==============

2.1 Runlevel planning
---------------------

   Runlevels are a convenient way of changing a system's current purpose
 on the fly by terminating and starting a bulk of running programs at once.
 If you are not confident with runlevels and init, I suggest you get yourself
 some information on it now. Search for primers on the web and read init(8). 

   You'll have to choose what runlevels you want to use before you begin,
 too. Somewhat default runlevels are thus:


 RUNLEVEL: | DESCRIPTION:
 ----------+----------------------
         0 | Power down
         S | Single user mode
         1 | Alias for S
         2 | Multi user runlevel with console login
         3 | Alias for 2
         4 | Alias for 2
         5 | Multi user runlevel with graphical login
         6 | Reboot
 ----------+----------------------

   I don't recommend changing the purpose of runlevels 0, 6 and S because
 they should be configured like this for many programs - we'll stick with
 their function in this hint. Because I use only 3 modes for booting
 (Single User, Console Multi User and Graphical Multi User) runlevels 4 and 5
 are aliases (realised with symlinks) for runlevel 2 (default). You can change
 their purpose to whatever you like, but I suggest you'll do that after you
 finished this hint.


2.2 Directory layout
--------------------

   To give you an idea of how BSD init works, I'll show you the final directory
 layout:
 
 /etc/rc.d
    + rc.sysinit# system initialization
    + rc.0# shutdown
    + rc.1# single user
    + rc.2# multi user
    + rc.3# linked to rc.2
    + rc.4# linked to rc.2
    + rc.5# multi user with graphical login
    + rc.6# reboot, linked to rc.0
    + rc.local# local extensions of rc.sysinit

 ...and maybe later, to your liking, these and more:
    + rc.firewall
    + rc.daemons
    + rc.netdaemons
    + rc.nfs
    + rc.nis

 I suggest you create the directory and basic files (the first list) now.

    In the following section I will give you the contents of each of those
 files; these are resembling my own - but the parts that may not be applicable
 to anyone are commented out shell-style with a '#'. Please take a close look
 at these lines and decide whether you need them.


2.3 Setting up the inittab
--------------------------

   The inittab resides in /etc and configures your init. Before you start
 writing it, you should realize that a wrong inittab will probably result (in
 the worst case) in a kernel panic, but at least a lot of trouble booting your
 system. 

   Now let's get down to business! Put this in your /etc/inittab:


-------------------------------/etc/inittab----------------------------------
id:2:initdefault:

si:S:sysinit:/etc/rc.d/rc.sysinit

l0:0:wait:/etc/rc.d/rc.0
l1:1:wait:/etc/rc.d/rc.1
l2:2:wait:/etc/rc.d/rc.2
l3:3:wait:/etc/rc.d/rc.3
l4:4:wait:/etc/rc.d/rc.4
l5:5:wait:/etc/rc.d/rc.5
l6:6:wait:/etc/rc.d/rc.6

ca:12345:ctrlaltdel:/sbin/shutdown -t1 -r now

su:S1:respawn:/sbin/sulogin

c1:2345:respawn:/sbin/agetty tty1 38400 linux
c2:2345:respawn:/sbin/agetty tty2 38400 linux
c3:2345:respawn:/sbin/agetty tty3 38400 linux
c4:2345:respawn:/sbin/agetty tty4 38400 linux
c5:2345:respawn:/sbin/agetty tty5 38400 linux
c6:2345:respawn:/sbin/agetty tty6 38400 linux
----------------------------end of /etc/inittab------------------------------

   This is a pretty basic configuration but should do for about everybody. As
 you can see, init first starts /etc/rc.d/rc.sysinit and then loads the needed
 file for the default runlevel (/etc/rc.d/rc.2).


3 Creating the boot scripts
===========================

3.1 Creating essential scripts
------------------------------

   Let's create /etc/rc.d/rc.sysinit first:


-----------------------------/etc/rc.d/rc.sysinit----------------------------
#!/bin/sh
echo "Mounting root device read-only..."
/bin/mount -n -o remount,ro /

### this would be a good spot for hdparm, because
### the whole boot process will benefit from it!

echo "Initializing swap partitions..."
/sbin/swapon -a

/sbin/fsck -A -a -C
if [ $? -gt 1 ]; then
   echo
   echo "ERROR:"
   echo "Your filesystem has been severely damaged. You can probably correct this"
   echo "problem by running e2fsck manually (eg. with the -v and -y options). After"
   echo "you logout, the system will reboot."
   echo
   PS1="(Repair filesystem)# "
   export PS1
   /sbin/sulogin
   /bin/umount -a -r
   /sbin/reboot -f
fi

echo "Remounting root device read-write..."
/bin/mount -n -v -o remount,rw /

echo "" >/etc/mtab
/bin/mount -f -o remount,rw /

echo "Mounting other local filesystems..."
/bin/mount -a -v -tnonfs

echo "Setting up hostname..."
/bin/hostname `cat /etc/HOSTNAME |cut -d . -f1`
/bin/domainname `cat /etc/HOSTNAME |cut -d . -f2-`

if [ -f "/etc/random-seed" ]; then
  echo "Initializing random number generator..."
  /bin/cat /etc/random-seed >/dev/urandom
  rm -f /etc/random-seed
fi

### removing stale PID files is good, too
# echo "Removing stale PID files..."
# /bin/rm /var/run/*.pid
# /bin/rm /etc/dhcpc/*.pid

echo "Loading keymap..."
/usr/bin/loadkeys -d

### I also suggest setting keyboard repeat rate and delay here:
# echo "Setting keyboard rate (30) and delay (250)..."
# /usr/bin/kbdrate -r 30 -d 250

### And the console font as well:
# echo "Setting console font..."
# /usr/bin/setfont lat9u-12.psfu.g

### And if you like to have numlock on:
# echo "Setting numlock on VTs 1-12 to on..."
# for tty in /dev/tty; do
# /usr/bin/setleds +num < $tty
# done

### mplayer likes this...
# echo "Configuring RTC..."
# echo 1024 > /proc/sys/dev/rtc/max-user-freq

echo "Setting system time from hardware clock..."
/sbin/hwclock --hctosys --utc

echo "Starting system and kernel log daemons...."
/usr/sbin/syslogd
/usr/sbin/klogd -c3

### Use modules? If yes, uncomment this:
# echo "Updating module dependencies..."
# /sbin/depmod -a

### You may find this useful when you have some (non-networking) daemons
### and an extra .rc-file for them:
# echo "Starting daemons..."
# if [ -x /etc/rc.d/rc.daemons ]; then
# /etc/rc.d/rc.daemons
# fi
-------------------------end of /etc/rc.d/rc.sysinit-------------------------


   To make the hostname lines work as expected, create a file /etc/HOSTNAME
 which holds your FQDN (Full Qualified Domain Name). That is, for example,
 foo.bar.com or gimli.gimli.org. A last note on the hwclock command: if your system
 clock isn't configured for using UTC (that means you're using local time) you
 should drop the --utc options from that line. Read the 'time' hint for more
 information.

   Now let's create the script for the single user runlevel. Since this
 runlevel won't be used very often to boot in, but instead to fall back to if
 something happens to the system, all running programs will be killed so you're
 in a very clean environment when running in single user mode.
 

--------------------------------/etc/rc.d/rc.1-------------------------------
#!/bin/sh
echo "Unmounting remote filesystems..."
/bin/umount -a -tnfs

# insert a line for each network card you use here. This is an example for
#  a single network card set-up (configured as eth0):
#
# echo "Bringing down network interface eth0..."
# /sbin/ifconfig eth0 down

echo "Sending all processes the TERM signal..."
/sbin/killall5 -15
sleep 1

echo "Sending all processes the KILL signal..."
/sbin/killall5 -9
----------------------------end of /etc/rc.d/rc.1----------------------------


   If this script has run, no daemons have been left except the kernel daemons
 and init. After it has finished sulogin will be started (that's what the line
 "su:S1:respawn:/sbin/sulogin" is for :) so only root can use the system. All
 virtual consoles will be disabled.

   Let's get on to the next script, /etc/rc.d/rc.2. This file has many common
 options in it, eg. to set up networking and start network daemons. Remove
 every line you won't use, but don't add anything before you read chapter 4.


--------------------------------/etc/rc.d/rc.2-------------------------------
#!/bin/sh
# In this example, the network card is configured with 192.168.0.2 as ip
#  address and a netmask of 255.255.255.0. This network card uses 192.168.0.1
#  as the default gateway. This is the set up you would use if the box
#  192.168.0.1 would be the gateway.

### You may wish to add some commands changing sysctl states here, for example:
# echo 1 > /proc/sys/net/ipv4/ip_forward# enable IP forwarding
# echo 1 > /proc/sys/net/ipv4/tcp_syncookies# defend against SYN flood

echo "Setting up loopback networking..."
/sbin/ifconfig lo 127.0.0.1
/sbin/route add -net 127.0.0.0 netmask 255.0.0.0 lo

echo "Setting up eth0..."
/sbin/ifconfig eth0 192.168.0.1 broadcast 192.168.0.255 netmask 255.255.255.0
/sbin/route add -net default gw 192.168.0.1 netmask 0.0.0.0

echo "Mounting remote filesystems..."
/bin/mount -a -v -tnfs

### you can create additional scripts for specific (networking) tasks,
### for example NFS, which needs a lot of daemons to work (see 3.2)
### or your firewall script:

# if [ -x /etc/rc.d/rc.firewall ]; then
#echo "Restoring firewall rules..."
#/etc/rc.d/rc.firewall
# fi

# if [ -x /etc/rc.d/rc.netdaemons ]; then
#echo "Starting network daemons..."
#/etc/rc.d/rc.netdaemons
# fi


if [ -x /etc/rc.d/rc.local ]; then
/etc/rc.d/rc.local
fi
----------------------------end of /etc/rc.d/rc.2----------------------------


   Now copy /etc/rc.d/rc.2 to /etc/rc.d/rc.5 and link the
   aliases for runlevel 2:
 ln -sf /etc/rc.d/rc.2 /etc/rc.d/rc.3
ln -sf /etc/rc.d/rc.2 /etc/rc.d/rc.4
cp /etc/rc.d/rc.2 /etc/rc.d/rc.5

    and add the following to the
 bottom of the file /etc/rc.d/rc.5:


------------------------------------snip-------------------------------------
echo "Starting graphical login manager..."

if [ -x /opt/kde/bin/kdm ]; then
/opt/kde/bin/kdm -nodaemon
elif [ -x /usr/bin/gdm ]; then
/usr/bin/gdm -nodaemon
elif [ -x /usr/X11R6/bin/xdm ]; then
/usr/X11R6/bin/xdm -nodaemon
else
echo "You chose to start graphical login mode, but you don't have either KDM or"
echo "GDM or XDM installed. This script looks for these display managers in the"
echo "following locations:"
echo
echo "   KDM      /opt/kde/bin/kdm"
echo "   GDM      /usr/bin/gdm"
echo "   XDM      /usr/X11R6/bin/xdm"
echo
echo "This message will go away in 10 seconds, and after that you will be dropped"
echo "in runlevel 2."
sleep 10
/sbin/telinit 2 
fi
----------------------------end of /etc/rc.d/rc.5----------------------------


   The script is pretty self-explaining. It looks for the most commonly used
 display managers in their default locations. If none of them is found, a
 warning will be displayed and the system will change to runlevel 2 with a
 normal console login screen. If you have a specific display manager you
 can leave out the 'if' and the others, of course.

   Now we have created all bootscripts except /etc/rc.d/rc.0 and
 /etc/rc.d/rc.6. Since they both perform pretty much the same function, we'll
 create it only once:


--------------------------------/etc/rc.d/rc.0-------------------------------
#!/bin/sh
echo "Sending all processes the TERM signal..."
/sbin/killall5 -15
sleep 1

echo "Sending all processes the KILL signal..."
/sbin/killall5 -9
sleep 1

echo "Deactivating swap partitions..."
/sbin/swapoff -a

echo "Saving random seed to a temporary file..."
/bin/dd if=/dev/urandom of=/etc/random-seed count=1 bs=512 2>/dev/null

echo "Saving the system time to hardware clock..."
/sbin/hwclock --systohc --utc

echo "Unmounting remote filesystems..."
/bin/umount -a -f -tnfs

case "" in
*6)
/sbin/reboot -w
;;

*0)
/sbin/halt -w
;;
esac

echo "Remounting root filesystem read-only..."
/bin/mount -n -o remount,ro /

echo "Flushing filesystem buffers..."
/bin/sync

echo "Unmounting local filesystems..."
/bin/umount -a -tnonfs

case "" in
*6)
echo "Please stand by while rebooting..."
/sbin/reboot -d -f -i
;;

*0)
echo "Bye..."
/sbin/halt -d -f -p
;;
esac
----------------------------end of /etc/rc.d/rc.0----------------------------


   Some notes on this file: the hwclock should be configured like the one in
 /etc/rc.d/rc.sysinit (no --utc if your hardware clock uses local time). The
 construction

  case "" in
*6)
/sbin/reboot -w
;;

*0)
/sbin/halt -w
;;
  esac

 writes some status information to /etc/wtmp. It's a good idea to do this,
 but you can safely remove it. At about two-third of the file, I call
 /bin/sync. This program flushes the filesystem buffers so you won't lose any
 data. Like the construct above this is optional but I recommend it.

   Now that we have created all the required files, some changes have to made to
 make them work. Run the following commands to do this:

chmod 754 /etc/rc.d/rc.0 /etc/rc.d/rc.1 /etc/rc.d/rc.2
chmod 754 /etc/rc.d/rc.3 /etc/rc.d/rc.sysinit
ln -s /etc/rc.d/rc.2 /etc/rc.d/rc.4
ln -s /etc/rc.d/rc.0 /etc/rc.d/rc.6

   You're done! Take a deep breath, type (as root) "reboot" and watch
 your system boot with BSD style init scripts! If you have troubles using
 these scripts, drop me a line: leslie.polzer@gmx.net.


3.2 Creating extra scripts
--------------------------

   As you probably know, it is common to have a /etc/rc.d/rc.local file where
 you put commands in that will be executed at the very end of the boot process.
 You can use it to create up-to-date issue files or to pick a random
 message of the day. But since you created all bootscripts yourself,
 you can change them as much as you like, and you probably won't need this
 script. So what's it going to be?

   I personally recommend you create this script, for the purpose of
 portability. Many daemons write one or two lines to this file, and it saves
 you trouble if it's already present. This is how you create one:

   Put this in a file /etc/rc.d/rc.local:

-------------------------------/etc/rc.d/rc.local----------------------------
#!/bin/sh
-----------------------------end /etc/rc.d/rc.local--------------------------

  And make it executable:

chmod 754 /etc/rc.d/rc.local

   It is very easy for you to disable /etc/rc.d/rc.local; just remove
 the executable flag from the script and it will be skipped at boot time.

 When I showed you the synopsis of rc.d/, I also told you that you can
 create extra files. You might put your iptables/ipchains lines for your
 firewall into rc.firewall and call it from rc., or you may stuff
 all daemons essential to NFS into rc.nfs and call that from another
 script called rc.netdaemons, in which you start all networking daemons.
 
     Do what you like best - BSD init is IMHO closer to human thinking
 than SysVInit.
 
   As a final tip in this section, I would like to point out to you that I
 have often had a multi-user environment without networking. It would be a
 good practice for you to set up this environment on, for example, runlevel 5
 and set it up in a secure way. This implies you have to decide whether you
 really need a service or not, to avoid any damage that may be caused by your
 ignorance.


4 Final Words
=============
   I hope you learnt from this hint how a BSD style init works. Although this
 setup is not the same as Slackware's or BSD's setup, the idea is basically the
 same. If you have comments on this hint, be they positive or negative,
 please mail me at leslie.polzer@gmx.net.
   I would like to thank all the people who emailed me so far, fixing bugs
 in the hint.


CHANGELOG:
[2005-02-16]
 * runlevel organization fixes

[2005-01-08]
 * changed permissions from 755 to 754 (thanks to Randy McMurchy)
 * removed linking from rc.2 to rc.5 - these are different files
   (thanks to George Boudreau from DIY Linux)
 * moved syncing before umounting (thanks to Noturno)

[2004-09-10]
 * changed /tmp/random-seed to /etc/random-seed in case
   /tmp is mounted as tmpfs (thanks to C. T. Waley)

[2004-06-05]
 * corrected a typo
 * corrected a mistake where runlevel 3 would be 5

[2003-10-02]
 * New maintainer 
 * Conversion to new hint format

原文转自：http://www.ltesting.net