Linux system startup process (2)

Kernel design style:

RedHat, SUSE
Core: Dynamic load kernel module
Kernel:/lib/modules/"kernel version number command directory"/
vmlinuz-2.6.32
/lib/modules/2.6.32/

Redhat5:ramdisk-->initrd
Redhat6:ramfs-->initramfs






Single core: Linux (LWP lightweight process)
Core: KO (Kernel object)



So ()

Microkernel: Windows, Solaris (threads)

Chroot:chroot/path/to/temproot [COMMAND ...]
Chroot/test/virrrot/bin/bash

Ldd/path/to/binary_file: Shows the shared libraries on which the binaries depend




MBR (bootloader)--Kernel-INITRD (INITRAMFS)--(ROOTFS)--/sbin/init (/etc/inittab)
/etc/inittab,/etc/init/*.conf
Upstart

Init/etc/inittab
Id:runlevels:action:process

Id:5:initdefault:

Si::sysinit:/etc/rc.d/rc.sysinit
OS Initialization

L0:0:WAIT:/ETC/RC.D/RC 0
rc0.d/
k*
Stop
s*
Start

/ETC/RC.D/INIT.D,/ETC/INIT.D

Service class Script:
Start

SysV:/ETC/RC.D/INIT.D
Start|stop|restart|status
Reload|configtest

Chkconfig

# chkconfig:runlevels SS KK when chkconfig command to create a link for this script in the RC#.D directory, runlevels represents a link that is created by default to start with s*-a link that does not have a level default of s*; The default is to create a link that starts with k*;
The start priority at the back of S is the number represented by SS, and the number after K is closed in order of precedence for KK;
# Description: A simple function to illustrate this script; \, continue.

Chkconfig--list: View the startup settings of all independent daemons; Independent daemon!
Chkconfig--list service_name

Chkconfig--add service_name

Chkconfig--del service_name

Chkconfig [--level runlevels] service_name {On|off}
If the ellipsis level is specified, the default is level 2,345;


Sample script:
#!/bin/bash
#
# chkconfig:2345 77 22
# description:test Service
#
Lockfile=/var/lock/subsys/myservice

Status () {
If [-e $LOCKFILE]; Then
echo "Running ..."
Else
echo "Stopped."
Fi
}

Usage () {
echo "' basename $ ' {start|stop|restart|status}"
}

Case $ in
Start
echo "Starting ..."
Touch $LOCKFILE;;
Stop
echo "Stopping ..."
Rm-f $LOCKFILE &>/dev/null
;;
Restart
echo "Restarting ...";;
Status
status;;
*)
usage;;
Esac


/etc/rc.d/rc.local: The system finally starts a service, exactly said, should execute a script;


/etc/inittab's Mission:
1, set the default operating level;
2, run the system initialization script;
3. Run the script in the directory corresponding to the specified run level;
4, set the operation of Ctrl+alt+del combination key;
5, define the UPS power supply in the power failure/recovery operation performed;
6, start the virtual terminal (2,345 level);
7, start the graphics terminal (5 level);



Type of daemon:
Independent Daemon Process
XINETD: Super Daemon, Agent
Transient daemon: No need to correlate to runlevel



Core:/boot/vmlinuz-version
Kernel module (KO):/lib/modules/version/

Kernel design:
Single Core
Modular design
Micro-core

Loading module:
Insmod
Modprobe

Www.kernel.org:



How user space accesses and monitors the kernel:
/proc,/sys

Pseudo file System

/proc/sys: Many of the files in this directory are readable and writable
/sys/: Some files can be written


To set kernel parameter values:
echo VALUE >/proc/sys/to/somefile
Sysctl-w kernel.hostname=

be effective immediately, but not permanently;

Permanently valid:/etc/sysctl.conf

Once the modified file is complete, the following command will take effect immediately:
Sysctl-p
SYSCTL-A: Show all kernel parameters and their values



Kernel Module Management:
Lsmod: View

Modprobe mod_name: Loading a module
Modprobe-r mod_name: Uninstalling a module

Modinfo mod_name: View specific information about the module

Insmod/path/to/module_file: Load Module
Rmmod Mod_name

Depmod/path/to/modiles_dir

Linux system startup process (2)