Transcript UNIX - SigmaNet

Unix Startup
Guntis Barzdins
Girts Folkmanis
Juris Krūmiņš
System Lifecycle: Ups &
Downs
Power
on
Power
off
Boot
Kernel
Init
OS
Init
RUN!
Shut
down
Boot Terminology
 Loader:
Program that moves bits from disk (usually)
to memory and then transfers CPU control to the newly
“loaded” bits (executable).
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 Bootloader / Bootstrap:

Program that loads the “first program” (the kernel).
 Boot PROM / PROM Monitor / BIOS:

Persistent code that is “already loaded” on power-up.
 Boot Manager:
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Program that lets you choose the “first program” to load.
LILO: LInux LOader
 A versatile boot manager that supports:
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Choice of Linux kernels.
Boot time kernel parameters.
Booting non-Linux kernels.
A variety of configurations.
 Characteristics:
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Lives in MBR or partition boot sector.
Has no knowledge of filesystem structure so…
Builds a sector “map file” (block map) to find kernel.
 /sbin/lilo – “map installer”.

/etc/lilo.conf is lilo configuration file.
Example lilo.conf File
boot=/dev/hda
map=/boot/map
install=/boot/boot.b
prompt
timeout=50
default=linux
image=/boot/vmlinuz-2.2.12-20
label=linux
initrd=/boot/initrd-2.2.12-20.img
read-only
root=/dev/hda1
LILO v.s. GRUB
 LILO
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Run LILO to modify mini-bootloader in the MBR
Cannot read file system itself
 GRUB
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Multistage loader
Can read file-system itself
 Parameter passing (runlevel, init) to kernel

Actually hacking – modifies address and name inside kernel for
the process to start
Init process (1)
init
When the kernel has started itself (has been loaded into memory, has
started running, and has initialised all device drivers and data structures
and such), it finishes its own part of the boot process by starting a user
level program, init. Thus, init is always the first process (its process
number is always 1).
The kernel looks for init in a few locations that have been historically used
for it, but the proper location for it (on a Linux system) is /sbin/init. If the
kernel can't find init, it tries to run /bin/sh, and if that also fails, the startup
of the system fails.
When init starts, it finishes the boot process by doing a number of
administrative tasks, such as checking filesystems, cleaning up /tmp,
starting various services, and starting a getty for each terminal and virtual
console where users should be able to log in (see Chapter 10).
Unix Process Hierarchy
[0]
/etc/inittab
Daemon
e.g. httpd
init [1]
Login shell
Child
Child
Grandchild
Child
Grandchild
pstree
Kernel threads, not real processes
Forked processes for network connections
Startup Sequence
Power-on
Boot
loader
LILO
Initialisation Scripts
Create
init
process
Linux
hardware
rc.sysinit
Load
Kernel
runlevel
0-6
rc.local
Ready
Different Unix startup files..
 Unix systems are usually based in the
AT&T System III & V or BSD work.
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Sun Mircosystems Solaris 2.X (formally SunOS) BSD-ish
DEC OSF/1 is BSD-ish (DEC use to do Ultrix)
IBM AIX (neither ATT or BSD but something else)
HP HP-UX (BSD-ish)
Silicon Graphics, IRIX (ATTish)
SCO (Santa Cruz Operation) PC unix (ATT)
Linux, kernel from Linus Torvalds (BSD-ish for admin,
ATT-ish for programming)
 Distributions Slackware, Redhat, SuSE, Debian

other free PC Unixs, NetBSD, 386BSD, free BSD
Startup files
 How to start other services not in kernel?
 BSD mode
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/etc/rc, /etc/rc.boot and /etc/rc.local
 System V
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Startup runlevels
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init process and /etc/inittab file
On linux:
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0: shutdown and halt
1 single-user mode
2 multiuse mode, no file sharing
3 full multiuser.
4 unused
5 X windows console
6 shuts down and reboots
Sample BSD Startup Scripts
/etc/rc.boot
 First rc script to run is /etc/rc.boot
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The first two lines set HOME and PATH environment variables
Executes basic system commands during boot
hostname file in /etc for each network interface

enables IP networking on each interface
Sample BSD Startup Scripts
/etc/rc.boot (cont.)
 Address or hostname of default Internet gateway is read
from /etc/defaultrouter
 non-local NW connections up prior to more complicated
routing in boot process
 /usr filesystem read-only for system check to see if
/fastboot exists
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Yes: system shut down cleanly~ filesystems in consistent state
No: all filesystems listed in /etc/fstab checked in fsck
 If disks check cleanly~ rc.boot runs /etc/rc.single
Sample BSD Startup Scripts
/etc/rc.single
 Commands in /etc/rc.single are executed at boot time
even if not using single mode
 Remounts / and /usr filesystems read/write

if not remounted~ system not able to come up
 Cleans out /etc/mtabfile and adds entries for / and /usr

was previously mounted but not in mtab file because root
filesystem not writable
 /usr/kvm mounted~ clean up shared library cache
Sample BSD Startup Scripts
/etc/rc.single
 /etc/utmp file cleaned out

contains user list of current log ins
 tzsetup command sets local time zone & status of daylight
savings time (kernal is GMT)
 loadkeys command sets keyboard mapping
 rc.single exits~rc.boot exits
 No problems in autoboot mode the next init process is
/etc/rc
 If problem~single-user (sh process) on console
Sample BSD Startup Scripts
/etc/rc
 /etc/rc is the main system startup up script in autoboot
after rc.boot
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if single-user: rc after shell is terminated
 if root filesystems not writable~ rerun rc.single
 clean up shared library cache
 remove /fastboot file
 /etc/passwd file edited ~system crashes

vipw and /etc/rc script make sure password file not destroyed
at crash
Sample BSD Startup Scripts
/etc/rc (cont.)
 Enable quotas
 /bin/ps -u cleans out the ps database (status of
processes)
 /etc/nologin created by shutdown to prevent logins during
shutdown
 executes rc.local script
 swapon -a to make use of all swap partitions listed in
etc/fstab
 expreserve: looks in /tmp to find files that were edited
when system went down
Sample BSD Startup Scripts
/etc/rc (cont.)
 Start standard system daemons (i.e., lpd, inetd,
update, uushed)
Sample BSD Startup Scripts
/etc/rc.local
 /etc/rc.local contains commands for local system
 portmap daemon maps RPC (remote procedure call)
service numbers to the NW ports of appropriate servers
 NIS (NW info service) Domain Name set from /etc/default
domain
 set subnet mask of all machines interfaces
 default route reset~ if no default routing daemon run
 list current configuration of NW interfaces on console
Sample BSD Startup Scripts
/etc/rc.local (cont.)
 All NFS filesystems mounted
 named (server for Domain Name system) maps between
hostnames and Internet addresses
 Client side NFS daemon run (biod)
 syslogd: responsible for managing log messages
 save kernel core dump in /var/crash/hostname

Image saved on swap partition~ save image to real filesystem
 Clean up temporary mail lock files and start sendmail
Sample BSD Startup Scripts
/etc/rc.local (cont.)
 Make machine NFS Server if filesystems need to be
exported
 Daemon to support diskless clients
 rpc.statd and rpc.lockd manage advisory locks on
NFS filesystems
 Start automount daemon
 3rd party vendor install scripts
 Appletalk protocol stack started
 Licensed software add-ons
System V Run Levels
 Level 0 – shutdown
 Level 1 or S – single-user mode
 Level 2 thru 5 – multi-user mode
 Level 6 - reboot
Startup Script Directories
 /etc/inittab tells init where scripts are
 /etc/init.d script directory
 /etc/rc2.d link to script directory
Startup files
 Understanding /etc/inittab

Label:runlevel:action:process
id:5:initdefault:
# System initialization.
si::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
Some Linux inittab action valus
Action
Meaning
Boot
Runs when system boots
Bootwait
Init waits for complete
Ctrlaltdel
Initdefault
Set the detault runlevel
off
Disable the entry
Once
For every runlevel
Powerfail
When init receive SIGPWR signal
Powerokwait
SIGPWR and /etc/powerstatus has ok
Respawn
Restart the process wheneven it termincates
Sysinit
Before any boot
Wait
Upon entrying the run mode and waits to
complete
Linux startup - rc.sysinit script
 /etc/rc.d/rc.sysinit - does a range of basic tasks including
 configures networking
 sets host name
 checks the root file system for repairs
 check root file system quota & turns quotas for groups and
users
 mount non-root file systems and checks them for repairs
 turns on swapping (virtual memory subsystem)
 checks and loads modules (drivers)

(see /var/log/messages)
Linux Run Levels
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Linux defines 7 run levels
Each run level defines a set of commands that are run to stop and start
processes.
The actual commands are held in /etc/init.d directory
The run level directories rc0.d, rc2.d…rc6.d contain links to the actual
commands
Each command is prefixed with S or K and a number 00-99
 S prefix means that a process should be started e.g.
S10network
 K prefix means that a process should be stopped (killed)
K70syslog
 The numbers determine the order in which the commands are
run from lowest first to highest last
Linux Run Levels 0-2
 Runlevel 0 Directory /etc/rc.d/rc0.d

Actually shutdown sequence
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Kill all processes
Turn off virtual memory system (i.e. swap partition)
unmounts swap and file systems
 Runlevel 1 /etc/rc.d/rc1.d
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single user mode
used for maintenance by system administrators when they
need sole control of machine, e.g. reconfiguring hardware
installing software
 Runlevel 2 /etc/rc.d/rc2.d
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Multi-user + networking (minus NFS)
Linux Run level 3-6
 Runlevel 3 /etc/rc.d/rc3.d
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Default run level
multi-user + NFS
 Runlevel 4 /etc/rc.d/rc4.d
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not defined ( available for customization)
 Runlevel 5 /etc/rc.d/rc5.d
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Same as 3 under Redhat this but includes starting X windows
 Runlevel 6 /etc/rc.d/rc6.d
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reboot
similar to 0 but allow allows option to shutdown (halt) or reboot
Shutdown
 shutdown allows...
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users to be warned the systems is going down
the contents of disk caches to be written disk
file systems to be marked as having been closed properly (
avoid file system check on next startup)
 Access to the shutdown command is restricted (it is in
/sbin)
 eg shutdown -h now
h = halt
r = reboot
Init scripts in Gentoo
 Named (not numbered) run levels.
 Smart dependencies.

Scripts can ‘use’ or ‘depend’ on others.
 Start / Stop / Pause.
 /etc/runlevels/default/.
Internet Daemon
 Daemon inetd started at boot time
 Configuration file /etc/inetd.conf

Name, type, protocol, wait-status, uid, server,
arguments
#
ftp
stream
tcp6
nowait
root
/usr/sbin/tcpd
in.ftpd
telnet
stream
tcp6
nowait
root
/usr/sbin/tcpd
in.telnetd
#
# Mail is a useful thing...
pop3
stream
tcp
nowait
root
/etc/mail/popper
popper -s
imap
stream
tcp
nowait
root
/etc/mail/imapd
imapd
Internet Daemon
 When to modify inetd.conf

Disable a service
Add a # at the beginning of the entry
 Send hang-up to inetd

kill –HUP processid
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Enable a service
Change the path
Modify arguments
Extended Internet Daemon
 Daemon xinetd
 Configuration file /etc/xinetd.conf and /etc/xinetd.d

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Attribute/value pair
Diable = yes/no
Setup automatic Mounting
/etc/fstab
/etc/vfstab
# Device
Mpoint FStype Opt Dump Pass
/dev/sd01sf /new ufs rw 0
2
/dev/da0b none swap sw 0 0
Sample Directory Tree with
Mount Points
/
/dev/hda9
/boot
/dev/hda1
/usr
/dev/hda5
/home
/dev/hda6
swap
/dev/hda7
/var
/dev/hda8
Mounting and Unmounting File
Systems
 File Systems mounted with the mount command:
mount [options] device directory
For example:
mount –o rw –t ext2 /dev/hda10 /tmp
 File systems umounted with the umount command:
umount [-f] directory
For example:
umount /tmp
 File systems should only be umounted when they are not in use.
/etc/fstab
 Configuration file for all partitions known to the system.
 Entry format:
/dev/device /dir/to/mount fstype
parameters fs_freq fs_passno
Sample entry:
/dev/hda10
/tmp ext2 defaults 1 2
 For entries in /etc/fstab, can run mount command with just mount
point:
> mount /tmp
To mount all file systems:
> mount -a
Scheduling processes - cron
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Many aspects of system administration require things to be
done on a routine basis
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Rotating logs
building help files
checking disk space
checking permissions
Remembering to do thing is error prone
Unix provides scheduling mechanism refereed to as cron.
Cron has two parts
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Daemon - crond
table of actions /etc/crontab
Cron
 the crond Daemon is started at boot time
 the daemon ‘wakes up’ every minute to check its
table of actions
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if their is something to do -> run command
if nothing to do --> go back to sleep for 1 min
 Cron table is a list (time,commnd) pairs. The
format is
 minute hour day month dayofweek command
Crontab
 Commands can be scheduled by
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minute (0 59)
Hour ( 0 to 23)
Day of the month (1 - 31)
Month ( 1 to 12)
Day of the week (0=Sunday 6 = sat, or use mon,tues,wed)
 Example
01 * * * *
* 1 * * *
04 1 * * *
* means ‘check every’
commnd2
# hourly at 1 minute past
commnd2
# daily at 1 am
commands 3 - run at 4 minute past
1 each day
Cron
 Under Redhat Linux the cron table is used to execute a
set of commands in some special directories
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/etc/cron.hourly
/etc/cron.daily
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contains logrotate, makewhatis,slocate,tmpwatch
/etc/cron.weekly
/etc/cron.monthly
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You can add you own commands to the appropriate directory, but
remember they need to be ‘batch’ commands as they will run
automatically
Crontab Files
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Minute 0-59
Hour 0-23
Day 1-31
Month 1-12
Weekday 0-6 (0=Sunday)
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* Matches everything
1-3 Matches range
1,5 Matches Series
Examples
15,45 10 * * 1-5
write garth % Hi Garth % get a job
30 2 * * 1 (cd /user/joe/p; make)
find /tmp –atime +3 –exec rm –f {} ‘;’
 Output mailed to owner of crontab file
crontab commands
 crontab
 crontab
 crontab
 crontab
 crontab


Replace ^C exit
–l List
–e Edit
–l > cronfile
cronfile
cron.allow
cron.deny
Common Uses for CRON
 Cleaning the filesystem
 Distribution of config files
 Rotating log files
 Backups
Webmin
 Webmin is a web-based interface for system
administration for Unix. Using any browser that
supports tables and forms (and Java for the File
Manager module), you can setup user accounts,
Apache, DNS, file sharing and so on.
 http://www.webmin.com
Advanced Boot Concepts
 Initial ramdisk (initrd) – two-stage boot for flexibility:
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First mount “initial” ramdisk as root.
Execute linuxrc to perform additional setup, configuration.
Finally mount “real” root and continue.
See Documentation/initrd.txt for details.
Also see “man initrd”.
 Net booting:


Remote root (Diskless-root-HOWTO).
Diskless boot (Diskless-HOWTO).
System initialization
 Overview of the PC Boot Process

When a PC is powered on, the BIOS (Basic
Input-Output System) runs first, followed by
a boot loader and finally the operating
system initialization routine.
System initialization
 The BIOS


When power is initially applied to the computer this triggers
the RESET pin on the processor. This causes the processor to
read from memory location 0xFFFFFFF0 and begin executing
the code located there. This address is mapped to the ReadOnly Memory (ROM) containing the BIOS. The BIOS must poll
the hardware and set up an environment capable of booting
the operating system. BIOS functionality can be broken into
three areas: Power On Self Test (POST), Setup and Boot.
The last action of the BIOS is to execute the 19h interrupt,
which loads the first sector of the first boot device. Since this
is the location of the boot loader, execution of the 19h interrupt
transfers control to the boot loader.
System initialization
 The Boot Loader
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

Once the BIOS loads the first sector of the boot device into RAM,
the boot loader begins execution. In the case of a hard drive, this
first sector is referred to as the Master Boot Record (MBR). The
MBR contains the partition table describing the partitions defined on
the hard drive. It also contains a program, the boot loader, which
will load the first sector of the partition marked as active into RAM
and execute it.
The size of the MBR is limited to one sector on disk or 512 bytes,
since it is located within the first sector of the drive at cylinder 0,
head 0, sector 1.
Typically boot loaders have been highly integrated with the
operating system that they support. This integration cuts down on
the operations a boot loader must perform, making a 512 byte boot
loader feasible. When more functionality is required, a multi-stage
boot loader may be used.
A multi-stage boot loader provides more function and flexibility by
working around the 512 byte size limitation. Rather than consisting
of a single program which loads the operating system directly,
multi-stage boot loaders divide their functionality into a number of
smaller programs that each successively load one another.
System initialization
 OS Initialization
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Once the boot loader has loaded the OS image into memory,
control is transferred to the OS.
A large aspect of initialization for any operating system is the
establishment of virtual memory management. On an Intelbased system this typically involves setting up the Global
Descriptor Table (GDT), creating a Local Descriptor Table
(LDT), switching the processor into protected memory mode,
setting up page directories and enabling paging.
Additional tasks include device driver initialization and the
assignment of interrupts in the Interrupt Descriptor Table (IDT).
Another major initialization task is establishing support for
various file system types and mounting a root file system.
System initialization
 OS Initialization




The initial process must explicitly do for itself all the tasks
accomplished by a call to fork(). This initial process,
numbered 0 on UNIX systems.
Process 0 must be able to self-generate its own process
context. Once this context has been established, the system
has the capability to suspend and resume execution of
Process 0 just as it would any other process. Once
established, the role of Process 0 differs by operating
system.
Process 1, commonly referred to as the init process, is the
first process forked from Process 0.
Once Process 1 has been forked from Process 0, often a
number of additional kernel space processes are created to
handle additional kernel space tasks. Once all of these are
running, the kernel space operating system initialization is
complete.
System initialization
System initialization
 OpenBSD employs a two-stage boot loading process, if one
does not count the MBR as a separate “stage.” The first stage is
handled by a boot loader program called biosboot, while the
secondary boot loader is called simply boot.
 The boot program sets up an environment suitable for
transferring control to the kernel image. It also provides an
interactive prompt for user input of additional boot parameters.
The main tasks of the boot program are:
1. Switching the CPU into protected mode
2. Probing for console devices and displaying subsequent
messages to the discovered consoles
3. Detecting memory, both that reported by the BIOS and
extended memory
4. Detecting if the BIOS supports Advanced Power
Management (APM)
System initialization
System initialization
System initialization
1. A “pagedaemon” process to handle page swapping for
the virtual memory subsystem,
2. A “reaper” process to free the resources still allocated
to dead processes,
3. A “cleaner” process to clear out dirty buffers found in
the BQ_DIRTY buffer queue,
4. An “update” process for synchronizing the file systems,
5. An “aiodoned” process for handling completed
asynchronous I/O operations,
System initialization
 With all kernel threads running, only a few finishing
touches are needed. The random number generator is
seeded and the generation of process identification
numbers is set up such that each successive process
will be given a larger pseudo-random number than its
predecessor. At this point, Process 0 finally enters its
main loop by calling uvm_scheduler(). This function
has Process 0 continually check for processes that are
in a runnable state but not resident in memory and
swaps them in. Control never returns to the main()
function from this call and one could say the operating
system is truly running.
System initialization
System initialization
System initialization
Userspace system initialization
 Historically there are two initialization systems :


System V
BSD
 These two system differ with names, script running order,
directory hierarchy which hold initialization scripts.
 Linux systems mainly use System V initialization system.
Exclude Slackware, whose initialization system very
similar to BSD.
Userspace system initialization
 Kernel start up root file system in ro mode and run init process
 As a result we have:
 ro file system
 init process
 The next system step initializing user space environment greatly
depends on init configuration file /etc/inittab
 It’s very important to understand that until this moment it doesn’t
matter what initialization system will be used.
Userspace system initialization
 INIT


Starting from this point next system behavior greatly
depend on how init program configuration created.
Because kernel mount root file system in ro mode init
process can access it’s configuration file /etc/inittab.
Userspace system initialization
1.
2.
3.
4.
5.
6.
7.
8.
When it’s time to create process, the kernel first of all try to run program
mentioned in rdinit= boot option.
If rdinit= boot option didn’t specify path to init programm, kernel try to run /init
If there’s no /init program, kernel try to run program from init= boot option
If init= option didn’t specify path, kernel try /sbin/init
If there’s problem with /sbin/init, kernel try /etc/init
It there’s problem with /etc/init, then kernel try /bin/init
If there’s problem running /bin/init, then kernel try to run /bin/sh
If there’s problem with /bin/sh, then kernel panic with error message “No init
found ….”
Userspace system initialization
 Run levels



There are 7 runlevels: 0-6
System at any time working in one of this runlevels
You, as administrator of the system can switch system from
one runlevel to another using telinit or init programs

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
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

0 runlevel – shutdown system
1 runlevel – single user mode
2 runlevel – in most cases same as runlevel 3 but without network file system,
at least in RedHat or SUSE linux
3 runlevel – multiuser mode.
4 runlevel – In Slackware used for GUI login. RedHat and SUSE linux don’t
use this runlevel.
5 runlevel – RedHat and SUSE linux use for GUI login. Slackware don’t use
this level
6 runlevel – system reboot level
Userspace system initialization
 Slackware system initialization:


Slackware system initialization use BSD style system
initialization scripts.
All scripts are in /etc/rc.d directory
Userspace system initialization
/etc/rc.d/rc.S file


1.
2.
3.
Based in /etc/inittab file rc.S file will be executed the first one
no matter which runlevel system will run.
Based on #!/bin/sh we can tell, that it’s a shell script.
First of all we define PATH environment variable
PATH=/sbin:/usr/sbin:/bin:/usr/bin
Then we mount proc filesystem to /proc diretory
/sbin/mount -v proc /proc -n -t proc
Userspace system initialization
4. Check if we can run hotplug system
if [ -w /proc/sys/kernel/hotplug ]; then
if grep -w nohotplug /proc/cmdline 1> /dev/null 2> /dev/null ; then
echo "/dev/null" > /proc/sys/kernel/hotplug
elif [ ! -x /etc/rc.d/rc.hotplug ]; then
echo "/dev/null" > /proc/sys/kernel/hotplug
fi
fi
5. Check if we can run devfs script and use devfs filesystem
if [ -x /etc/rc.d/rc.devfsd ]; then
/etc/rc.d/rc.devfsd start
fi
Userspace system initialization
6. Check if we can use virtual sysfs filesystem
if [ -d /sys ]; then
if cat /proc/filesystems | grep -w sysfs 1> /dev/null 2> /dev/null then
if ! cat /proc/mounts | grep -w sysfs 1> /dev/null 2> /dev/null then
/sbin/mount -v sysfs /sys -n -t sysfs
fi
fi
fi
7.Check if it’s possible to run udev programm.
if [ -x /etc/rc.d/rc.udev ]; then
if ! grep -w nohotplug /proc/cmdline 1> /dev/null 2> /dev/null; then
/etc/rc.d/rc.udev
fi
fi
Userspace system initialization
8. Turn on all swap filesystem
/sbin/swapon -a
9. Check what mode root filesystem have been mounted
READWRITE=no
if touch /fsrwtestfile 2>/dev/null; then
rm -f /fsrwtestfile
READWRITE=yes
else
echo "Testing root filesystem status: read-only filesystem"
fi
10. Check is it necessary to force file system check:
if [ -r /etc/forcefsck ]; then
FORCEFSCK="-f"
fi
Userspace system initialization
11. Check if it’s necessary to check root filesystem
if [ ! -r /etc/fastboot ]; then
echo "Checking root filesystem:" /sbin/fsck $FORCEFSCK -C -a / RETVAL=$?
fi
12. Check fsck program return code
if [ $RETVAL -ge 2 ]; then
if [ $RETVAL -ge 4 ]; then
echo PS1="(Repair filesystem) \#"; export PS1
sulogin
else
echo
fi
echo "Unmounting file systems."
/sbin/umount -a -r
/sbin/mount -n -o remount,ro /
echo "Rebooting system."
sleep 2
reboot -f
fi
Userspace system initialization
13. Ir 12 pint are ok, then remount root filesystem in rw mode
/sbin/mount -w -v -n -o remount /
if [ $? -gt 0 ] ; then
echo
read junk;
fi
Userspace system initialization
14. Set system time
if [ -x /sbin/hwclock ]; then
if grep "^UTC" /etc/hardwareclock 1> /dev/null 2> /dev/null ; then
echo "Setting system time from the hardware clock (UTC)."
/sbin/hwclock --utc --hctosys
else
echo "Setting system time from the hardware clock (localtime)."
/sbin/hwclock --localtime --hctosys
fi
fi
15. Try to load kernel modules
if [ -x /etc/rc.d/rc.modules -a -r /proc/modules ]; then
. /etc/rc.d/rc.modules
fi
Userspace system initialization
16. Try to load sysctl kernel configuration
if [ -x /sbin/sysctl -a -r /etc/sysctl.conf ]; then
/sbin/sysctl -e -p /etc/sysctl.conf
fi
17. If there’s no /etc/fastboot file, then other file systems will be checked.
if [ ! -r /etc/fastboot ]; then
/sbin/fsck $FORCEFSCK -C -R -A -a
fi
18. Mount all file systems from /etc/fstab file except ntfs and smbfs file systems
/sbin/mount -a -v -t nonfs,nosmbfs,noproc
Userspace system initialization
19. Repeatedly turn on swap filesystem
/sbin/swapon -a
20. Delete temporary files
( cd /var/log/setup/tmp && rm -rf * ) /bin/rm -f /var/run/utmp /var/run/*pid /etc/nologin
/var/run/lpd* \ /var/run/ppp* /etc/dhcpc/*.pid /etc/forcefsck /etc/fastboot
21. If kernel use initrd technology, then turn off RAM disk, delete initrd directory and free
memory
if [ -d /initrd ]; then
/sbin/umount /initrd 2> /dev/null
rmdir /initrd 2> /dev/null
blockdev --flushbufs /dev/ram0 2> /dev/null
fi
Userspace system initialization
22. Create utmp file
touch /var/run/utmp
chown root.utmp /var/run/utmp
chmod 664 /var/run/utmp
23. Create motd file
echo "$(/bin/uname -sr)." > /etc/motd
24. If it’s necessary we can use System V initialization scripts
if [ -x /etc/rc.d/rc.sysvinit ]; then . /etc/rc.d/rc.sysvinit
fi
Userspace system initialization
25. Create everything for random number generator
if [ -f /etc/random-seed ]; then
echo "Using /etc/random-seed to initialize /dev/urandom."
cat /etc/random-seed > /dev/urandom
fi
if [ -r /proc/sys/kernel/random/poolsize ]; then
dd if=/dev/urandom of=/etc/random-seed count=1 \
bs=$(cat /proc/sys/kernel/random/poolsize) 2> /dev/null
else
dd if=/dev/urandom of=/etc/random-seed count=1 bs=512 2> /dev/null
fi
chmod 600 /etc/random-seed
Userspace system initialization
 /etc/rc.d/rc.modules user direct modprobe program
execution to load kernel modules. All you have to do –
uncomment needed module, ex.:
/sbin/modprobe 3c503
 /etc/rc.d/rc.modules is also used for loading network card
modules, by the means of executing
/etc/rc.d/rc.netdevice script
if [ -x /etc/rc.d/rc.netdevice ]; then
. /etc/rc.d/rc.netdevice
fi
Userspace system initialization
 /etc/rc.d/rc.S script used for:
 Activating swap space
 File system check
 File system mounting
 Loading kernel modules, loading network drivers and
so on, by executing /etc/rc.d/rc.modules script
 Some other system startup behavior
Userspace system initialization
/etc/rc.d/rc.M script

1.
/etc/rc.d/rc.M script used to bring system to 2, 3 and 4 runlevel.
Going multiuser:
echo "Going multiuser..."
2. Set terminal parameters:
/bin/setterm -blank 15 -powersave powerdown -powerdown 60
3. Check /etc/HOSTNAME file and set system hostname
if [ -r /etc/HOSTNAME ]; then
/bin/hostname $(cat /etc/HOSTNAME | cut -f1 -d .)
else
echo "darkstar.example.net" > /etc/HOSTNAME /bin/hostname darkstar
fi
Userspace system initialization
4. Save all kernel messages to /var/log/dmesg file:
/bin/dmesg -s 65536 > /var/log/dmesg
5. Start up SYSLOG daemon:
if [ -x /etc/rc.d/rc.syslog -a -x /usr/sbin/syslogd -a -d /var/log ] then
. /etc/rc.d/rc.syslog start
fi
6. Starp up pcmcia controller support
if [ -x /etc/rc.d/rc.pcmcia ] ; then
. /etc/rc.d/rc.pcmcia start
if [ -r /var/run/cardmgr.pid ]; then
sleep 5
fi
fi
Userspace system initialization
7. Start up network phase 1 initialization
if [ -x /etc/rc.d/rc.inet1 ]; then
. /etc/rc.d/rc.inet1
fi
8. Hotplug support start up
if [ -x /etc/rc.d/rc.hotplug -a -r /proc/modules ]; then
if ! grep nohotplug /proc/cmdline 1> /dev/null 2> /dev/null ; then
echo "Activating hardware detection: /etc/rc.d/rc.hotplug start"
. /etc/rc.d/rc.hotplug start
fi
fi
Userspace system initialization
9. Start up network phase 2 initialization
if [ -x /etc/rc.d/rc.inet2 ]; then
. /etc/rc.d/rc.inet2
fi
10. Remove temporary files
/bin/rm -f /var/lock/* /var/spool/uucp/LCK..* \
/tmp/.X*lock /tmp/core /core 2> /dev/null
11. Change root directory access mode and set sticky bit on /tmp and /var/tmp directory
chmod 755 / 2> /dev/null
chmod 1777 /tmp /var/tmp
Userspace system initialization
12. Create dynamic loadable library cache
if [ -x /sbin/ldconfig ]; then
echo "Updating shared library links: /sbin/ldconfig"
/sbin/ldconfig
fi
13. Start simple DNS cache server
if [ -x /etc/rc.d/rc.dnsmasq ]; then /etc/rc.d/rc.dnsmasq start
fi
14. Starp up CUPS un LPRng print system
if [ -x /etc/rc.d/rc.cups ]; then
/etc/rc.d/rc.cups start
elif [ -x /etc/rc.d/rc.lprng ]; then
. /etc/rc.d/rc.lprng start
fi
Userspace system initialization
15. Start up support for “BSD accounting” subsystem
if [ -x /sbin/accton -a -r /var/log/pacct ]; then
/sbin/accton /var/log/pacct
chmod 640 /var/log/pacct
echo "Process accounting turned on."
fi
16. Start cron daemon
if [ -x /usr/sbin/crond ]; then
/usr/sbin/crond -l10 >>/var/log/cron 2>&1
fi
17. Start atd
if [ -x /usr/sbin/atd ]; then
/usr/sbin/atd -b 15 -l 1
fi
Userspace system initialization
18. Start up disk quota mechanism
if grep -q quota /etc/fstab ; then
if [ -x /sbin/quotacheck ]; then
echo "Checking filesystem quotas: /sbin/quotacheck -avugm"
/sbin/quotacheck -avugm
fi
if [ -x /sbin/quotaon ]; then
echo "Activating filesystem quotas: /sbin/quotaon -avug"
/sbin/quotaon -avug
fi
fi
19. Start up sendmail system
if [ -x /etc/rc.d/rc.sendmail ]; then
. /etc/rc.d/rc.sendmail start
fi
Userspace system initialization
20. The last one will be /etc/rc.d/rc.local script, which
is used for customize system start up and execute
applications without System V or BSD initialization
scripts.
Userspace system initialization
 If we need to execute script upon system start up we
need to set execution permissions on this script
 And vice versa, if we don’t need to execute this service,
don’t make it executable.
 Every start up script – relatively simple shell script. It may
handle command line parameters like: start – to start
service, and stop – to stop service
 If you don’t have initialization script for certain application
we handle this situation in 2 different way:
Userspace system initialization
1.
2.
Make /etc/rc.d/rc.local script execute this program
Write down your own start up script and add
information about new script to /etc/rc.d/rc.M
Userspace system initialization
 Script example for custom service using /etc/rc.d/rc.M start up mechanism
#! /bin/bash
start()
{
echo “Program started”
program_start
}
stop()
{
echo “Program stoped”
killall program
}
case $1 in
start) start ;;
stop) stop ;;
restart) stop sleep 2 start ;;
*) echo “Usage: Program start|stop|restart”
esac
Userspace system initialization
 Add this script to /etc/rc.d/rc.M script by entering
if [ -x /etc/rc.d/rc.script ]; then
. /etc/rc.d/rc.script start
fi