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52.第十二章 Linux启动和内核管理 -- CentOS 的启动管理(一)

2021-11-22 12:02:28 阅读：688 来源： 互联网

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第十二章 Linux启动和内核管理

内容概述

CentOS 6 之前版本的启动流程
服务管理
Grub管理
启动排错
内核管理
CentOS 7 以后版本启动流程
Unit介绍
服务管理和查看
启动排错
破解root口令
修复Grub2

1.CentOS 6 的启动管理

1.1 Linux 组成

kernel 实现进程管理、内存管理、网络管理、驱动程序、文件系统、安全功能等功能
rootfs 包括程序和 glibc 库
程序：二进制执行文件

库：函数集合, function, 调用接口（头文件负责描述）

1.2 内核设计流派

宏内核(monolithic kernel)：又称单内核和强内核，Unix，Linux

把所有系统服务都放到内核里，所有功能集成于同一个程序，分层实现不同功能，系统庞大复杂，Linux其实在单内核内核实现了模块化，也就相当于吸收了微内核的优点
微内核(micro kernel)：Windows，Solaris，HarmonyOS

简化内核功能，在内核之外的用户态尽可能多地实现系统服务，同时加入相互之间的安全保护，每种功能使用一个单独子系统实现，将内核功能移到用户空间，性能差

1.3 CentOS 6 启动流程

1.3.1 CentOS 6 启动流程

在这里插入图片描述

加载BIOS的硬件信息，获取第一个启动设备
读取第一个启动设备MBR的引导加载程序(grub)的启动信息
加载核心操作系统的核心信息，核心开始解压缩，并尝试驱动所有的硬件设备
核心执行init程序，并获取默认的运行信息
init程序执行/etc/rc.d/rc.sysinit文件，重新挂载根文件系统
启动核心的外挂模块
init执行运行的各个批处理文件(scripts)
init执行/etc/rc.d/rc.local
执行/bin/login程序，等待用户登录
登录之后开始以Shell控制主机

1.3.2 硬件启动POST

POST：Power-On-Self-Test，加电自检，是BIOS功能的一个主要部分。负责完成对CPU、主板、内存、硬盘子系统、显示子系统、串并行接口、键盘等硬件情况的检测

主板的ROM：BIOS，Basic Input and Output System，保存着有关计算机系统最重要的基本输入输出程序，系统信息设置、开机加电自检程序和系统启动自举程序等

主板的RAM：CMOS互补金属氧化物半导体，保存各项参数的设定，按次序查找引导设备，第一个有引导程序的设备为本次启动设备

1.3.3 启动加载器 bootloader

1.3.3.1 grub 功能和组成

bootloader: 引导加载器，引导程序

windows: ntloader，仅是启动OS
Linux：功能丰富，提供菜单，允许用户选择要启动系统或不同的内核版本；把用户选定的内核装载到内存中的特定空间中，解压、展开，并把系统控制权移交给内核Linux的bootloader
LILO：LInux LOader，早期的bootloader，功能单一
GRUB: GRand Unified Bootloader, CentOS 6 GRUB 0.97: GRUB Legacy， CentOS 7 以后使用GRUB 2.02

GRUB 启动阶段

primary boot loader :

1st stage：MBR的前446个字节

1.5 stage：mbr 之后的扇区，让stage1中的bootloader能识别stage2所在的分区上的文件系统
secondary boot loader ：2nd stage，分区文件/boot/grub/

范例：

[root@centos6 ~]# hexdump -C -n 512 /dev/sda
00000000  eb 48 90 00 00 00 00 00  00 00 00 00 00 00 00 00  |.H..............|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 03 02  |................|
00000040  ff 00 00 20 01 00 00 00  00 02 fa 90 90 f6 c2 80  |... ............|
00000050  75 02 b2 80 ea 59 7c 00  00 31 c0 8e d8 8e d0 bc  |u....Y|..1......|
00000060  00 20 fb a0 40 7c 3c ff  74 02 88 c2 52 f6 c2 80  |. ..@|<.t...R...|
00000070  74 54 b4 41 bb aa 55 cd  13 5a 52 72 49 81 fb 55  |tT.A..U..ZRrI..U|
00000080  aa 75 43 a0 41 7c 84 c0  75 05 83 e1 01 74 37 66  |.uC.A|..u....t7f|
00000090  8b 4c 10 be 05 7c c6 44  ff 01 66 8b 1e 44 7c c7  |.L...|.D..f..D|.|
000000a0  04 10 00 c7 44 02 01 00  66 89 5c 08 c7 44 06 00  |....D...f.\..D..|
000000b0  70 66 31 c0 89 44 04 66  89 44 0c b4 42 cd 13 72  |pf1..D.f.D..B..r|
000000c0  05 bb 00 70 eb 7d b4 08  cd 13 73 0a f6 c2 80 0f  |...p.}....s.....|
000000d0  84 f0 00 e9 8d 00 be 05  7c c6 44 ff 00 66 31 c0  |........|.D..f1.|
000000e0  88 f0 40 66 89 44 04 31  d2 88 ca c1 e2 02 88 e8  |..@f.D.1........|
000000f0  88 f4 40 89 44 08 31 c0  88 d0 c0 e8 02 66 89 04  |..@.D.1......f..|
00000100  66 a1 44 7c 66 31 d2 66  f7 34 88 54 0a 66 31 d2  |f.D|f1.f.4.T.f1.|
00000110  66 f7 74 04 88 54 0b 89  44 0c 3b 44 08 7d 3c 8a  |f.t..T..D.;D.}<.|
00000120  54 0d c0 e2 06 8a 4c 0a  fe c1 08 d1 8a 6c 0c 5a  |T.....L......l.Z|
00000130  8a 74 0b bb 00 70 8e c3  31 db b8 01 02 cd 13 72  |.t...p..1......r|
00000140  2a 8c c3 8e 06 48 7c 60  1e b9 00 01 8e db 31 f6  |*....H|`......1.|
00000150  31 ff fc f3 a5 1f 61 ff  26 42 7c be 7f 7d e8 40  |1.....a.&B|..}.@|
00000160  00 eb 0e be 84 7d e8 38  00 eb 06 be 8e 7d e8 30  |.....}.8.....}.0|
00000170  00 be 93 7d e8 2a 00 eb  fe 47 52 55 42 20 00 47  |...}.*...GRUB .G|
00000180  65 6f 6d 00 48 61 72 64  20 44 69 73 6b 00 52 65  |eom.Hard Disk.Re|
00000190  61 64 00 20 45 72 72 6f  72 00 bb 01 00 b4 0e cd  |ad. Error.......|
000001a0  10 ac 3c 00 75 f4 c3 00  00 00 00 00 00 00 00 00  |..<.u...........|
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 80 20  |............... |
000001c0  21 00 83 aa 28 82 00 08  00 00 00 00 20 00 00 aa  |!...(....... ...|
000001d0  29 82 83 fe ff ff 00 08  20 00 00 80 3c 0c 00 fe  |)....... ...<...|
000001e0  ff ff 83 fe ff ff 00 88  5c 0c 00 00 40 06 00 fe  |........\...@...|
000001f0  ff ff 05 fe ff ff 00 88  9c 12 00 78 63 06 55 aa  |...........xc.U.|
00000200
[root@centos6 ~]# hexdump -C -n 512 -v /dev/sda
00000000  eb 48 90 00 00 00 00 00  00 00 00 00 00 00 00 00  |.H..............|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 03 02  |................|
00000040  ff 00 00 20 01 00 00 00  00 02 fa 90 90 f6 c2 80  |... ............|
00000050  75 02 b2 80 ea 59 7c 00  00 31 c0 8e d8 8e d0 bc  |u....Y|..1......|
00000060  00 20 fb a0 40 7c 3c ff  74 02 88 c2 52 f6 c2 80  |. ..@|<.t...R...|
00000070  74 54 b4 41 bb aa 55 cd  13 5a 52 72 49 81 fb 55  |tT.A..U..ZRrI..U|
00000080  aa 75 43 a0 41 7c 84 c0  75 05 83 e1 01 74 37 66  |.uC.A|..u....t7f|
00000090  8b 4c 10 be 05 7c c6 44  ff 01 66 8b 1e 44 7c c7  |.L...|.D..f..D|.|
000000a0  04 10 00 c7 44 02 01 00  66 89 5c 08 c7 44 06 00  |....D...f.\..D..|
000000b0  70 66 31 c0 89 44 04 66  89 44 0c b4 42 cd 13 72  |pf1..D.f.D..B..r|
000000c0  05 bb 00 70 eb 7d b4 08  cd 13 73 0a f6 c2 80 0f  |...p.}....s.....|
000000d0  84 f0 00 e9 8d 00 be 05  7c c6 44 ff 00 66 31 c0  |........|.D..f1.|
000000e0  88 f0 40 66 89 44 04 31  d2 88 ca c1 e2 02 88 e8  |..@f.D.1........|
000000f0  88 f4 40 89 44 08 31 c0  88 d0 c0 e8 02 66 89 04  |..@.D.1......f..|
00000100  66 a1 44 7c 66 31 d2 66  f7 34 88 54 0a 66 31 d2  |f.D|f1.f.4.T.f1.|
00000110  66 f7 74 04 88 54 0b 89  44 0c 3b 44 08 7d 3c 8a  |f.t..T..D.;D.}<.|
00000120  54 0d c0 e2 06 8a 4c 0a  fe c1 08 d1 8a 6c 0c 5a  |T.....L......l.Z|
00000130  8a 74 0b bb 00 70 8e c3  31 db b8 01 02 cd 13 72  |.t...p..1......r|
00000140  2a 8c c3 8e 06 48 7c 60  1e b9 00 01 8e db 31 f6  |*....H|`......1.|
00000150  31 ff fc f3 a5 1f 61 ff  26 42 7c be 7f 7d e8 40  |1.....a.&B|..}.@|
00000160  00 eb 0e be 84 7d e8 38  00 eb 06 be 8e 7d e8 30  |.....}.8.....}.0|
00000170  00 be 93 7d e8 2a 00 eb  fe 47 52 55 42 20 00 47  |...}.*...GRUB .G|
00000180  65 6f 6d 00 48 61 72 64  20 44 69 73 6b 00 52 65  |eom.Hard Disk.Re|
00000190  61 64 00 20 45 72 72 6f  72 00 bb 01 00 b4 0e cd  |ad. Error.......|
000001a0  10 ac 3c 00 75 f4 c3 00  00 00 00 00 00 00 00 00  |..<.u...........|
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 80 20  |............... |
000001c0  21 00 83 aa 28 82 00 08  00 00 00 00 20 00 00 aa  |!...(....... ...|
000001d0  29 82 83 fe ff ff 00 08  20 00 00 80 3c 0c 00 fe  |)....... ...<...|
000001e0  ff ff 83 fe ff ff 00 88  5c 0c 00 00 40 06 00 fe  |........\...@...|
000001f0  ff ff 05 fe ff ff 00 88  9c 12 00 78 63 06 55 aa  |...........xc.U.|
00000200

[root@centos6 ~]# df -Th
Filesystem     Type   Size  Used Avail Use% Mounted on
/dev/sda2      ext4    97G  908M   91G   1% /
tmpfs          tmpfs  490M     0  490M   0% /dev/shm
/dev/sda1      ext4   976M   31M  895M   4% /boot
/dev/sda3      ext4    50G   74M   47G   1% /data

[root@centos6 ~]# modinfo ext4
filename:       /lib/modules/2.6.32-754.el6.x86_64/kernel/fs/ext4/ext4.ko
license:        GPL
description:    Fourth Extended Filesystem
author:         Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others
retpoline:      Y
srcversion:     3C0D8A8996992A22750E504
depends:        mbcache,jbd2
vermagic:       2.6.32-754.el6.x86_64 SMP mod_unload modversions 

[root@centos6 ~]# ll -h /lib/modules/2.6.32-754.el6.x86_64/kernel/fs/ext4/ext4.ko
-rwxr--r--. 1 root root 636K Jun 20  2018 /lib/modules/2.6.32-754.el6.x86_64/kernel/fs/ext4/ext4.ko

[root@centos6 ~]# fdisk -l

Disk /dev/sda: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0008a04f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1         131     1048576   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2             131       12910   102645760   83  Linux
/dev/sda3           12910       19437    52428800   83  Linux
/dev/sda4           19437       26109    53591040    5  Extended
/dev/sda5           19437       19698     2097152   82  Linux swap / Solaris

[root@centos7 ~]# fdisk -l

Disk /dev/sda: 214.7 GB, 214748364800 bytes, 419430400 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b65a1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200   211814399   104857600   83  Linux
/dev/sda3       211814400   316671999    52428800   83  Linux
/dev/sda4       316672000   419430399    51379200    5  Extended
/dev/sda5       316674048   320868351     2097152   82  Linux swap / Solaris

[root@centos6 ~]# ls /boot
config-2.6.32-754.el6.x86_64  grub                                 lost+found                        System.map-2.6.32-754.el6.x86_64
efi                           initramfs-2.6.32-754.el6.x86_64.img  symvers-2.6.32-754.el6.x86_64.gz  vmlinuz-2.6.32-754.el6.x86_64

[root@centos6 ~]# ls /boot/grub/
device.map     fat_stage1_5  grub.conf         jfs_stage1_5  minix_stage1_5     splash.xpm.gz  stage2         vstafs_stage1_5
e2fs_stage1_5  ffs_stage1_5  iso9660_stage1_5  menu.lst      reiserfs_stage1_5  stage1         ufs2_stage1_5  xfs_stage1_5

[root@centos6 ~]# cat /boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/sda2
#          initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz #加载图片
hiddenmenu
title CentOS 6 (2.6.32-754.el6.x86_64) #菜单
	root (hd0,0)
	kernel /vmlinuz-2.6.32-754.el6.x86_64 ro root=UUID=f26b3084-878f-4218-a7df-0eedd8cb79af rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet
	initrd /initramfs-2.6.32-754.el6.x86_64.img
#/vmlinuz-2.6.32-754.el6.x86_64  内核     root=UUID=55ed4e69-a262-485e-a2c8-9df9ac044aec  / 根分区UUID     initrd /initramfs-2.6.32-754.el6.x86_64.img  驱动文件

[root@centos6 ~]# blkid
/dev/sda1: UUID="07ff813e-74af-4047-88ad-c402b397fd1c" TYPE="ext4" 
/dev/sda2: UUID="f26b3084-878f-4218-a7df-0eedd8cb79af" TYPE="ext4" 
/dev/sda3: UUID="c8cea348-2536-46ae-9b3b-fe0543fbdc13" TYPE="ext4" 
/dev/sda5: UUID="66c77c3c-e56c-4df2-90fd-08150563b747" TYPE="swap"

[root@centos6 ~]# ls /boot
config-2.6.32-754.el6.x86_64  grub                                 lost+found                        System.map-2.6.32-754.el6.x86_64
efi                           initramfs-2.6.32-754.el6.x86_64.img  symvers-2.6.32-754.el6.x86_64.gz  vmlinuz-2.6.32-754.el6.x86_64
# initramfs-2.6.32-754.el6.x86_64.img  驱动文件    vmlinuz-2.6.32-754.el6.x86_64 内核文件

[root@centos6 ~]# file /boot/initramfs-2.6.32-754.el6.x86_64.img
/boot/initramfs-2.6.32-754.el6.x86_64.img: gzip compressed data, from Unix, last modified: Wed Oct  6 23:46:51 2021, max compression

[root@centos6 ~]# cp /boot/initramfs-2.6.32-754.el6.x86_64.img /data
cp: overwrite `/data/initramfs-2.6.32-754.el6.x86_64.img'? y
[root@centos6 ~]# cd /data
[root@centos6 data]# ls
initramfs-2.6.32-754.el6.x86_64.img  lost+found

[root@centos6 data]# mv initramfs-2.6.32-754.el6.x86_64.img initramfs-2.6.32-754.el6.x86_64.img.gz
[root@centos6 data]# gzip -d initramfs-2.6.32-754.el6.x86_64.img.gz

[root@centos6 data]# ls
initramfs-2.6.32-754.el6.x86_64.img  lost+found
[root@centos6 data]# ll -h initramfs-2.6.32-754.el6.x86_64.img 
-rw------- 1 root root 61M Nov  5 20:13 initramfs-2.6.32-754.el6.x86_64.img

[root@centos6 data]# ll /boot/initramfs-2.6.32-754.el6.x86_64.img -h
-rw-------. 1 root root 22M Nov  4 22:57 /boot/initramfs-2.6.32-754.el6.x86_64.img

[root@centos6 data]# file initramfs-2.6.32-754.el6.x86_64.img 
initramfs-2.6.32-754.el6.x86_64.img: ASCII cpio archive (SVR4 with no CRC)

[root@centos6 data]# cpio -id < initramfs-2.6.32-754.el6.x86_64.img 
123797 blocks
[root@centos6 data]# ls
bin      dracut-004-411.el6  init                initqueue-settled                    lib         mount      pre-pivot    proc  sysroot  var
cmdline  emergency           initqueue           initqueue-timeout                    lib64       netroot    pre-trigger  sbin  tmp
dev      etc                 initqueue-finished  initramfs-2.6.32-754.el6.x86_64.img  lost+found  pre-mount  pre-udev     sys   usr

[root@centos6 data]# find -name ext4.ko
./lib/modules/2.6.32-754.el6.x86_64/kernel/fs/ext4/ext4.ko

1.3.3.2 CentOS 6 grub 安装

安装 grub 两种方式

方法1: grub-install 安装grub stage1和stage1_5到/dev/DISK磁盘上，并复制GRUB相关文件到DIR/boot目录下

grub-install --root-directory=DIR /dev/DISK

方法2 : grub命令

#grub
grub> root (hd#,#)
grub> setup (hd#)

范例：修复grub的第1阶段故障

[root@centos6 ~]# hexdump -C -n 512 /dev/sda
00000000  eb 48 90 10 8e d0 bc 00  b0 b8 00 00 8e d8 8e c0  |.H..............|
00000010  fb be 00 7c bf 00 06 b9  00 02 f3 a4 ea 21 06 00  |...|.........!..|
00000020  00 be be 07 38 04 75 0b  83 c6 10 81 fe fe 07 75  |....8.u........u|
00000030  f3 eb 16 b4 02 b0 01 bb  00 7c b2 80 8a 74 03 02  |.........|...t..|
00000040  80 00 00 80 30 f2 04 00  00 08 fa 90 90 f6 c2 80  |....0...........|
00000050  75 02 b2 80 ea 59 7c 00  00 31 c0 8e d8 8e d0 bc  |u....Y|..1......|
00000060  00 20 fb a0 40 7c 3c ff  74 02 88 c2 52 f6 c2 80  |. ..@|<.t...R...|
00000070  74 54 b4 41 bb aa 55 cd  13 5a 52 72 49 81 fb 55  |tT.A..U..ZRrI..U|
00000080  aa 75 43 a0 41 7c 84 c0  75 05 83 e1 01 74 37 66  |.uC.A|..u....t7f|
00000090  8b 4c 10 be 05 7c c6 44  ff 01 66 8b 1e 44 7c c7  |.L...|.D..f..D|.|
000000a0  04 10 00 c7 44 02 01 00  66 89 5c 08 c7 44 06 00  |....D...f.\..D..|
000000b0  70 66 31 c0 89 44 04 66  89 44 0c b4 42 cd 13 72  |pf1..D.f.D..B..r|
000000c0  05 bb 00 70 eb 7d b4 08  cd 13 73 0a f6 c2 80 0f  |...p.}....s.....|
000000d0  84 f0 00 e9 8d 00 be 05  7c c6 44 ff 00 66 31 c0  |........|.D..f1.|
000000e0  88 f0 40 66 89 44 04 31  d2 88 ca c1 e2 02 88 e8  |..@f.D.1........|
000000f0  88 f4 40 89 44 08 31 c0  88 d0 c0 e8 02 66 89 04  |..@.D.1......f..|
00000100  66 a1 44 7c 66 31 d2 66  f7 34 88 54 0a 66 31 d2  |f.D|f1.f.4.T.f1.|
00000110  66 f7 74 04 88 54 0b 89  44 0c 3b 44 08 7d 3c 8a  |f.t..T..D.;D.}<.|
00000120  54 0d c0 e2 06 8a 4c 0a  fe c1 08 d1 8a 6c 0c 5a  |T.....L......l.Z|
00000130  8a 74 0b bb 00 70 8e c3  31 db b8 01 02 cd 13 72  |.t...p..1......r|
00000140  2a 8c c3 8e 06 48 7c 60  1e b9 00 01 8e db 31 f6  |*....H|`......1.|
00000150  31 ff fc f3 a5 1f 61 ff  26 42 7c be 7f 7d e8 40  |1.....a.&B|..}.@|
00000160  00 eb 0e be 84 7d e8 38  00 eb 06 be 8e 7d e8 30  |.....}.8.....}.0|
00000170  00 be 93 7d e8 2a 00 eb  fe 47 52 55 42 20 00 47  |...}.*...GRUB .G|
00000180  65 6f 6d 00 48 61 72 64  20 44 69 73 6b 00 52 65  |eom.Hard Disk.Re|
00000190  61 64 00 20 45 72 72 6f  72 00 bb 01 00 b4 0e cd  |ad. Error.......|
000001a0  10 ac 3c 00 75 f4 c3 00  00 00 00 00 00 00 00 00  |..<.u...........|
000001b0  00 00 00 00 00 00 00 00  4f a0 08 00 00 00 80 20  |........O...... |
000001c0  21 00 83 aa 28 82 00 08  00 00 00 00 20 00 00 aa  |!...(....... ...|
000001d0  29 82 83 fe ff ff 00 08  20 00 00 80 3c 0c 00 fe  |)....... ...<...|
000001e0  ff ff 83 fe ff ff 00 88  5c 0c 00 00 40 06 00 fe  |........\...@...|
000001f0  ff ff 05 fe ff ff 00 88  9c 12 00 78 63 06 55 aa  |...........xc.U.|
00000200

#破坏grub第1阶段
[[root@centos6 ~]# dd if=/dev/zero of=/dev/sda bs=1 count=446
446+0 records in
446+0 records out
446 bytes (446 B) copied, 0.000782486 s, 570 kB/s
[root@centos6 ~]# hexdump -C -n 512 /dev/sda
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 80 20  |............... |
000001c0  21 00 83 aa 28 82 00 08  00 00 00 00 20 00 00 aa  |!...(....... ...|
000001d0  29 82 83 fe ff ff 00 08  20 00 00 80 3c 0c 00 fe  |)....... ...<...|
000001e0  ff ff 83 fe ff ff 00 88  5c 0c 00 00 40 06 00 fe  |........\...@...|
000001f0  ff ff 05 fe ff ff 00 88  9c 12 00 78 63 06 55 aa  |...........xc.U.|
00000200

[root@centos6 ~]# hexdump -C -n 512 -v /dev/sda
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000060  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000070  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000000f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000100  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000120  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000130  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000140  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000150  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000160  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000170  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000190  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 80 20  |............... |
000001c0  21 00 83 aa 28 82 00 08  00 00 00 00 20 00 00 aa  |!...(....... ...|
000001d0  29 82 83 fe ff ff 00 08  20 00 00 80 3c 0c 00 fe  |)....... ...<...|
000001e0  ff ff 83 fe ff ff 00 88  5c 0c 00 00 40 06 00 fe  |........\...@...|
000001f0  ff ff 05 fe ff ff 00 88  9c 12 00 78 63 06 55 aa  |...........xc.U.|
00000200
#前446字节被清空

[root@centos6 ~]# reboot

在这里插入图片描述
一阶段被破坏，系统认为硬盘不能启动，自动从光盘启动

在这里插入图片描述
语言

在这里插入图片描述
键盘布局

在这里插入图片描述
网络不配置

在这里插入图片描述
Continue

在这里插入图片描述
/ 根分区被挂载到/mnt/sysimage

在这里插入图片描述

光盘启动，进入rescue模式
#chroot /mnt/sysimage  #切到根目录
#grub-install /dev/sda  #修复前446字节 
#sync #存盘
#exit #退出
#reboot #重启

在这里插入图片描述
系统可以正常启动

范例：

[root@centos6 ~]# grub
Probing devices to guess BIOS drives. This may take a long time.


    GNU GRUB  version 0.97  (640K lower / 3072K upper memory)

 [ Minimal BASH-like line editing is supported.  For the first word, TAB
   lists possible command completions.  Anywhere else TAB lists the possible
   completions of a device/filename.]
grub> root (hd0,0)
root (hd0,0)
 Filesystem type is ext2fs, partition type 0x83
grub> setup (hd0)
setup (hd0)
 Checking if "/boot/grub/stage1" exists... no
 Checking if "/grub/stage1" exists... yes
 Checking if "/grub/stage2" exists... yes
 Checking if "/grub/e2fs_stage1_5" exists... yes
 Running "embed /grub/e2fs_stage1_5 (hd0)"...  27 sectors are embedded.
succeeded
 Running "install /grub/stage1 (hd0) (hd0)1+27 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> quit
quit

1.3.3.3 grub legacy 管理

配置文件：/boot/grub/grub.conf <-- /etc/grub.conf

stage2及内核等通常放置于一个基本磁盘分区

grub legacy 功用：

(1) 提供启动菜单、并提供交互式接口

a：内核参数

e：编辑模式，用于编辑菜单

c：命令模式，交互式接口

(2) 加载用户选择的内核或操作系统

允许传递参数给内核

可隐藏启动菜单

(3) 为菜单提供了保护机制

为编辑启动菜单进行认证

为启用内核或操作系统进行认证

grub的命令行接口

help: 获取帮助列表
help KEYWORD: 详细帮助信息
find (hd#,#)/PATH/TO/SOMEFILE：
root (hd#,#)
kernel /PATH/TO/KERNEL_FILE: 设定本次启动的内核文件；额外还可添加许多内核支持使用的
cmdline参数

例如：max_loop=100 selinux=0 init=/path/to/init
initrd /PATH/TO/INITRAMFS_FILE: 设定为选定的内核提供额外文件的ramdisk
boot: 引导启动选定的内核

cat /proc/cmdline 内核参数

内核参数文档:

/usr/share/doc/kernel-doc-2.6.32/Documentation/kernel-parameters.txt

grub legacy识别硬盘设备

(hd#,#)
hd#: 磁盘编号，用数字表示；从0开始编号
#: 分区编号，用数字表示; 从0开始编号

示例：
(hd0,0) 第一块硬盘，第一个分区

手动在grub命令行接口启动系统

grub> root (hd#,#)
grub> kernel /vmlinuz-VERSION-RELEASE ro root=/dev/DEVICE
grub> initrd /initramfs-VERSION-RELEASE.img
grub> boot

grub legacy配置文件：/boot/grub/grub.conf

default=#: 设定默认启动的菜单项；落单项(title)编号从0开始
timeout=#：指定菜单项等待选项选择的时长
splashimage=(hd#,#)/PATH/XPM_FILE：菜单背景图片文件路径
password [--md5| --encrypt] STRING: 启动菜单编辑认证
hiddenmenu：隐藏菜单
title TITLE：定义菜单项“标题”, 可出现多次
root (hd#,#)：查找stage2及kernel文件所在设备分区；为grub的根
kernel /PATH/TO/VMLINUZ_FILE [PARAMETERS]：启动的内核
initrd /PATH/TO/INITRAMFS_FILE: 内核匹配的ramfs文件
password [--md5|--encrypted ] STRING: 启动选定的内核或操作系统时进行认证

grub加密生成grub口令

grub-md5-crypt
grub-crypt

破解root口令：

(1) 编辑grub菜单(选定要编辑的title，而后使用a 或 e 命令)
(2) 在选定的kernel后附加1, s, S，single 都可以进入单用户模式
(3) 在kernel所在行，键入“b”命令

范例：破解CentOS 6 root密码

在这里插入图片描述
按ESC，进入菜单选择，按a

在这里插入图片描述
在最后输入1，表示临时进入1模式，单用户模式

在这里插入图片描述

#不用密码直接进来了，passwd 直接修改密码
# passwd root

# init 3 #进入3模式

输入新密码直接登录

范例: 给grub 添加密码,防止破解root密码

[root@centos6 ~]# grub-crypt
Password: 
Retype password: 
$6$dd3QxTQiLvVTxITw$HGyYnMmaFsMA98nYgs8bDaccnw716Bm8i/toQeDRJFcYQ5L7hYdD7OKGTx30fsX9GFr7AGsByFj0SzHbZIAJY/
#设置grub生成密码

[root@centos6 ~]# vim /boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/sda2
#          initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
password --encrypt $6$dd3QxTQiLvVTxITw$HGyYnMmaFsMA98nYgs8bDaccnw716Bm8i/toQeDRJFcYQ5L7hYdD7OKGTx30fsX9GFr7AGsByFj0SzHbZIAJY/ #在这里设置grub密码
title CentOS 6 (2.6.32-754.el6.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.32-754.el6.x86_64 ro root=UUID=f26b3084-878f-4218-a7df-0eedd8cb79af rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet
	initrd /initramfs-2.6.32-754.el6.x86_64.img

[root@centos6 ~]# reboot

在这里插入图片描述
按ESC，进入菜单选择，按p

在这里插入图片描述
输入密码

在这里插入图片描述
只有输入密码才可以进到这里

忘记grub密码，直接去vim /boot/grub/grub.conf文件，把password --encrypt $6$dd3QxTQiLvVTxITw$HGyYnMmaFsMA98nYgs8bDaccnw716Bm8i/toQeDRJFcYQ5L7hYdD7OKGTx30fsX9GFr7AGsByFj0SzHbZIAJY/
这行删除就没有grub密码了

范例：生成背景图片

[root@centos6 ~]# convert -resize 640x480 -colors 14 winner.png splash.xpm
[root@centos6 ~]# more splash.xpm

#生成splash.xpm.gz
[root@centos6 ~]# gzip splash.xpm
[root@centos6 ~]# mv splash.xpm.gz /boot/grub

1.3. 加载 kernel

在这里插入图片描述
kernel 自身初始化过程

探测可识别到的所有硬件设备
加载硬件驱动程序（借助于ramdisk加载驱动）
以只读方式挂载根文件系统
运行用户空间的第一个应用程序：/sbin/init

Linux内核特点：

支持模块化：.ko（内核对象），如：文件系统，硬件驱动，网络协议等
支持内核模块的动态装载和卸载

内核组成部分：

核心文件：/boot/vmlinuz-VERSION-release

ramdisk：辅助的伪根系统，加载相应的硬件驱动，ramdisk --> ramfs 提高速度

CentOS 5 /boot/initrd-VERSION-release.img

CentOS 6 以后版本 /boot/initramfs-VERSION-release.img
模块文件：/lib/modules/VERSION-release

范例：误删除内核文件/boot/vmlinuz-2.6.32-754.el6.x86_64无法启动，故障恢复

[root@centos6 ~]# rm -f /boot/vmlinuz-2.6.32-754.el6.x86_64
[root@centos6 ~]# reboot

在这里插入图片描述
系统启动不了

在这里插入图片描述
按ESC ，选择光驱引导

在这里插入图片描述
进入光盘救援模式

在这里插入图片描述
语言

在这里插入图片描述
键盘布局

在这里插入图片描述
网络不配置

在这里插入图片描述
Continue

在这里插入图片描述
/ 根分区被挂载到/mnt/sysimage

在这里插入图片描述

#chroot /mnt/sysimage 切换到根目录
#mount /dev/sr0 /mnt/ #挂载光盘
#cp /mnt/isolinux/vmlinuz /boot/vmlinuz-2.6.32-754.el6.x86_64 #从光盘复制内核文件
#sync #存盘
#exit #退出
#reboot #重启

在这里插入图片描述

系统可以正常启动

ramdisk文件的制作：

mkinitrd命令

mkinitrd /boot/initramfs-$(uname -r).img $(uname -r)

dracut命令

dracut /boot/initramfs-$(uname -r).img $(uname -r)

范例：误删除/boot/initramfs-2.6.32-754.el6.x86_64.img无法启动，故障恢复

[root@centos6 ~]# rm -f /boot/initramfs-2.6.32-754.el6.x86_64.img
[root@centos6 ~]# reboot

在这里插入图片描述
按ESC ，选择光驱引导

在这里插入图片描述
进入光盘救援模式

在这里插入图片描述
语言

在这里插入图片描述
键盘布局

在这里插入图片描述
网络不配置

在这里插入图片描述
Continue

在这里插入图片描述
/ 根分区被挂载到/mnt/sysimage

在这里插入图片描述

#chroot /mnt/sysimage   #切换到根目录
#mkinitrd /boot/initramfs-`uname -r`.img `uname -r`  #生成驱动文件
#sync  #存盘
#exit  #退出
#reboot #重启

在这里插入图片描述

系统可以正常启动

1.3.5 init初始化

POST --> BootSequence (BIOS) --> Bootloader(MBR) --> kernel(ramdisk) --> rootfs(只读) --> init（systemd）

init程序的类型：

SysV: init, CentOS 5之前

配置文件：/etc/inittab

Upstart: init,CentOS 6

配置文件：/etc/inittab, /etc/init/*.conf

Systemd：systemd, CentOS 7

配置文件：/usr/lib/systemd/system

/etc/systemd/system

1.3.5.1 运行级别

运行级别：为系统运行或维护等目的而设定；0-6：7个级别，一般使用3, 5做为默认级别

0：关机
1：单用户模式(root自动登录), single, 维护模式
2：多用户模式，启动网络功能，但不会启动NFS；维护模式
3：多用户模式，正常模式；文本界面
4：预留级别；可同3级别
5：多用户模式，正常模式；图形界面
6：重启

切换级别：

init #

查看级别：

runlevel
who -r

定义运行级别

/etc/inittab

CentOS 5 的inittab文件还定义以下内容

初始运行级别(RUN LEVEL)
系统初始化脚本
对应运行级别的脚本目录
捕获某个关键字顺序
定义UPS电源终端/恢复脚本
在虚拟控制台生成getty
在运行级别5初始化X

CentOS 5 的inittab文件每一行格式：

id:runlevel:action:process

id：是惟一标识该项的字符序列
runlevels： 定义了操作所使用的运行级别
action： 指定了要执行的特定操作
		wait: 切换至此级别运行一次
		respawn：此process终止，就重新启动之
		initdefault：设定默认运行级别；process省略
		sysinit：设定系统初始化方式
process：定义了要执行的进程

范例：CentOS 5 的inittab文件

id:5:initdefault:
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
ca::ctrlaltdel:/sbin/shutdown -t3 -r now
pf::powerfail:/sbin/shutdown -f -h +2 "Power Failure; System Shutting Down”
pr:12345:powerokwait:/sbin/shutdown -c "Power Restored; Shutdown Cancelled”
1:2345:respawn:/sbin/mingetty 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
x:5:respawn:/etc/X11/prefdm -nodaemon

CentOS 6 /etc/inittab和相关文件

CentOS 6 init程序为 upstart, 其配置文件/etc/inittab, /etc/init/*.conf，配置文件的语法遵循 upstart配置文件语法格式，和CentOS5不同

/etc/inittab 设置系统默认的运行级别
/etc/init/control-alt-delete.conf
/etc/init/tty.conf
/etc/init/start-ttys.conf
/etc/init/rc.conf
/etc/init/prefdm.conf

范例：

[root@centos6 ~]# pstree -p
init(1)─┬─auditd(1165)───{auditd}(1166)
        ├─crond(1356)
        ├─master(1342)─┬─pickup(1350)
        │              └─qmgr(1351)
        ├─mingetty(1369)
        ├─mingetty(1371)
        ├─mingetty(1373)
        ├─mingetty(1375)
        ├─mingetty(1377)
        ├─mingetty(1379)
        ├─rsyslogd(1187)─┬─{rsyslogd}(1188)
        │                ├─{rsyslogd}(1190)
        │                └─{rsyslogd}(1191)
        ├─sshd(1263)─┬─sshd(1381)───bash(1383)───pstree(1405)
        │            └─sshd(1384)───sftp-server(1400)
        └─udevd(483)─┬─udevd(773)
                     └─udevd(783)
[root@centos6 ~]# cat /etc/inittab
# inittab is only used by upstart for the default runlevel.
#
# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# System initialization is started by /etc/init/rcS.conf
#
# Individual runlevels are started by /etc/init/rc.conf
#
# Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf
#
# Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,
# with configuration in /etc/sysconfig/init.
#
# For information on how to write upstart event handlers, or how
# upstart works, see init(5), init(8), and initctl(8).
#
# Default runlevel. The runlevels used are:
#   0 - halt (Do NOT set initdefault to this)
#   1 - Single user mode
#   2 - Multiuser, without NFS (The same as 3, if you do not have networking)
#   3 - Full multiuser mode
#   4 - unused
#   5 - X11
#   6 - reboot (Do NOT set initdefault to this)
# 
id:3:initdefault: #设置开机进入到哪个模式启动

[root@centos5 ~]# cat /etc/inittab 
#
# inittab       This file describes how the INIT process should set up
#               the system in a certain run-level.
#
# Author:       Miquel van Smoorenburg, <miquels@drinkel.nl.mugnet.org>
#               Modified for RHS Linux by Marc Ewing and Donnie Barnes
#

# Default runlevel. The runlevels used by RHS are:
#   0 - halt (Do NOT set initdefault to this)
#   1 - Single user mode
#   2 - Multiuser, without NFS (The same as 3, if you do not have networking)
#   3 - Full multiuser mode
#   4 - unused
#   5 - X11
#   6 - reboot (Do NOT set initdefault to this)
# 
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

# Trap CTRL-ALT-DELETE
ca::ctrlaltdel:/sbin/shutdown -t3 -r now

# When our UPS tells us power has failed, assume we have a few minutes
# of power left.  Schedule a shutdown for 2 minutes from now.
# This does, of course, assume you have powerd installed and your
# UPS connected and working correctly.  
pf::powerfail:/sbin/shutdown -f -h +2 "Power Failure; System Shutting Down"

# If power was restored before the shutdown kicked in, cancel it.
pr:12345:powerokwait:/sbin/shutdown -c "Power Restored; Shutdown Cancelled"


# Run gettys in standard runlevels
1:2345:respawn:/sbin/mingetty 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

# Run xdm in runlevel 5
x:5:respawn:/etc/X11/prefdm -nodaemon

1.3.5.2 初始化脚本 sysinit

[root@centos6 ~]# file /etc/rc.d/rc.sysinit
/etc/rc.d/rc.sysinit: Bourne-Again shell script text executable

[root@centos6 ~]# cat /etc/rc.d/rc.sysinit
#!/bin/bash
#
# /etc/rc.d/rc.sysinit - run once at boot time
#
# Taken in part from Miquel van Smoorenburg's bcheckrc.
#

HOSTNAME=$(/bin/hostname)

set -m

if [ -f /etc/sysconfig/network ]; then
    . /etc/sysconfig/network
fi
if [ -z "$HOSTNAME" -o "$HOSTNAME" = "(none)" ]; then
    HOSTNAME=localhost
fi

if [ ! -e /proc/mounts ]; then
	mount -n -t proc /proc /proc
	mount -n -t sysfs /sys /sys >/dev/null 2>&1
fi
if [ ! -d /proc/bus/usb ]; then
	modprobe usbcore >/dev/null 2>&1 && mount -n -t usbfs /proc/bus/usb /proc/bus/usb
else
	mount -n -t usbfs /proc/bus/usb /proc/bus/usb
fi

#remount /dev/shm to set attributes from fstab #669700
mount -n -o remount /dev/shm >/dev/null 2>&1
#remount /proc to set attributes from fstab #984003
mount -n -o remount /proc >/dev/null 2>&1

. /etc/init.d/functions

PLYMOUTH=
[ -x /bin/plymouth ] && PLYMOUTH=yes

# Check SELinux status
SELINUX_STATE=
if [ -e "/selinux/enforce" ] && [ "$(cat /proc/self/attr/current)" != "kernel" ]; then
	if [ -r "/selinux/enforce" ] ; then
		SELINUX_STATE=$(cat "/selinux/enforce")
	else
		# assume enforcing if you can't read it
		SELINUX_STATE=1
	fi
fi

if [ -n "$SELINUX_STATE" -a -x /sbin/restorecon ] && __fgrep " /dev " /proc/mounts >/dev/null 2>&1 ; then
	/sbin/restorecon -R -F /dev 2>/dev/null
fi

disable_selinux() {
	echo $"*** Warning -- SELinux is active"
	echo $"*** Disabling security enforcement for system recovery."
	echo $"*** Run 'setenforce 1' to reenable."
	echo "0" > "/selinux/enforce"
}

relabel_selinux() {
    # if /sbin/init is not labeled correctly this process is running in the
    # wrong context, so a reboot will be required after relabel
    AUTORELABEL=
    . /etc/selinux/config
    echo "0" > /selinux/enforce
    [ -n "$PLYMOUTH" ] && plymouth --hide-splash

    if [ "$AUTORELABEL" = "0" ]; then
	echo
	echo $"*** Warning -- SELinux ${SELINUXTYPE} policy relabel is required. "
	echo $"*** /etc/selinux/config indicates you want to manually fix labeling"
	echo $"*** problems. Dropping you to a shell; the system will reboot"
	echo $"*** when you leave the shell."
	start rcS-emergency

    else
	echo
	echo $"*** Warning -- SELinux ${SELINUXTYPE} policy relabel is required."
	echo $"*** Relabeling could take a very long time, depending on file"
	echo $"*** system size and speed of hard drives."

	/sbin/fixfiles -F restore > /dev/null 2>&1
    fi
    rm -f  /.autorelabel
    # at this point fsck was already executed see bz1236062
    [ -f /forcefsck ] && rm -f /forcefsck

    echo $"Unmounting file systems"
    umount -a
    mount -n -o remount,ro /
    echo $"Automatic reboot in progress."
    reboot -f
}

# Print a text banner.
echo -en $"\t\tWelcome to "
read -r system_release < /etc/system-release
if [[ "$system_release" == *"Red Hat"* ]]; then
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;31m"
 echo -en "Red Hat"
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;39m"
 PRODUCT=$(sed "s/Red Hat \(.*\) release.*/\1/" /etc/system-release)
 echo " $PRODUCT"
elif [[ "$system_release" == *Fedora* ]]; then
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;34m"
 echo -en "Fedora"
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;39m"
 PRODUCT=$(sed "s/Fedora \(.*\) \?release.*/\1/" /etc/system-release)
 echo " $PRODUCT"
elif [[ "$system_release" =~ "CentOS" ]]; then
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;36m"
 echo -en "CentOS"
 [ "$BOOTUP" = "color" ] && echo -en "\\033[0;39m"
 PRODUCT=$(sed "s/CentOS \(.*\) \?release.*/\1/" /etc/system-release)
 echo " $PRODUCT"
else
 PRODUCT=$(sed "s/ release.*//g" /etc/system-release)
 echo "$PRODUCT"
fi

# Only read this once.
cmdline=$(cat /proc/cmdline)

# Initialize hardware
if [ -f /proc/sys/kernel/modprobe ]; then
   if ! strstr "$cmdline" nomodules && [ -f /proc/modules ] ; then
       sysctl -w kernel.modprobe="/sbin/modprobe" >/dev/null 2>&1
   else
       # We used to set this to NULL, but that causes 'failed to exec' messages"
       sysctl -w kernel.modprobe="/bin/true" >/dev/null 2>&1
   fi
fi

touch /dev/.in_sysinit >/dev/null 2>&1

# Set default affinity
if [ -x /bin/taskset ]; then
   if strstr "$cmdline" default_affinity= ; then
     for arg in $cmdline ; do
         if [ "${arg##default_affinity=}" != "${arg}" ]; then
             /bin/taskset -p ${arg##default_affinity=} 1
             /bin/taskset -p ${arg##default_affinity=} $$
         fi
     done
   fi
fi

nashpid=$(pidof nash 2>/dev/null)
[ -n "$nashpid" ] && kill $nashpid >/dev/null 2>&1
unset nashpid

apply_sysctl

/sbin/start_udev

# Load other user-defined modules
for file in /etc/sysconfig/modules/*.modules ; do
  [ -x $file ] && $file
done

# Load modules (for backward compatibility with VARs)
if [ -f /etc/rc.modules ]; then
	/etc/rc.modules
fi

mount -n /dev/pts >/dev/null 2>&1
[ -n "$SELINUX_STATE" ] && restorecon -F /dev/pts >/dev/null 2>&1

# Configure kernel parameters
update_boot_stage RCkernelparam
apply_sysctl

# Set the hostname.
update_boot_stage RChostname
action $"Setting hostname ${HOSTNAME}: " hostname ${HOSTNAME}
[ -n "${NISDOMAIN}" ] && domainname ${NISDOMAIN}

# Sync waiting for storage.
{ rmmod scsi_wait_scan ; modprobe scsi_wait_scan ; rmmod scsi_wait_scan ; } >/dev/null 2>&1

# Device mapper & related initialization
if ! __fgrep "device-mapper" /proc/devices >/dev/null 2>&1 ; then
       modprobe dm-mod >/dev/null 2>&1
fi

if [ -f /etc/crypttab ]; then
    init_crypto 0
fi

if ! strstr "$cmdline" nompath && [ -f /etc/multipath.conf -a \
		-x /sbin/multipath ]; then
	modprobe dm-multipath > /dev/null 2>&1
	/sbin/multipath -v 0
	if [ -x /sbin/kpartx ]; then
                action_silent $"Add partition mappings: " /sbin/dmsetup ls --target multipath --exec "/sbin/kpartx -a -p p" 
	fi
fi

if ! strstr "$cmdline" nodmraid && [ -x /sbin/dmraid ]; then
	modprobe dm-mirror >/dev/null 2>&1
	dmraidsets=$(LC_ALL=C /sbin/dmraid -s -c -i)
	if [ "$?" = "0" ]; then
		for dmname in $dmraidsets; do
			if [[ "$dmname" == isw_* ]] && \
			   ! strstr "$cmdline" noiswmd; then
				continue
			fi
                        action_silent $"Activate software (ATA)RAID: " /sbin/dmraid -ay -i --rm_partitions -p "$dmname"
			/sbin/kpartx -a -p p "/dev/mapper/$dmname"
		done
	fi
fi

# Start any MD RAID arrays that haven't been started yet
[ -r /proc/mdstat -a -r /dev/md/md-device-map ] && action $"Run MD devices: " /sbin/mdadm -IRs

if [ -x /sbin/lvm ]; then
	if [ ! -f /.nolvm ] && ! strstr "$cmdline" nolvm ; then
		action $"Setting up Logical Volume Management:" /sbin/lvm vgchange -a ay --sysinit --ignoreskippedcluster
	else
		echo $"Logical Volume Management disabled at boot."
	fi
fi

if [ -f /etc/crypttab ]; then
    init_crypto 0
fi

if [ -f /fastboot ] || strstr "$cmdline" fastboot ; then
	fastboot=yes
fi

if [ -f /fsckoptions ]; then
	fsckoptions=$(cat /fsckoptions)
fi

if [ -f /forcefsck ] || strstr "$cmdline" forcefsck ; then
	fsckoptions="-f $fsckoptions"
elif [ -f /.autofsck ]; then
	[ -f /etc/sysconfig/autofsck ] && . /etc/sysconfig/autofsck
	if [ "$AUTOFSCK_DEF_CHECK" = "yes" ]; then
		AUTOFSCK_OPT="$AUTOFSCK_OPT -f"
	fi
	if [ -n "$AUTOFSCK_SINGLEUSER" ]; then
		[ -n "$PLYMOUTH" ] && plymouth --hide-splash
		echo
		echo $"*** Warning -- the system did not shut down cleanly. "
		echo $"*** Dropping you to a shell; the system will continue"
		echo $"*** when you leave the shell."
		[ -n "$SELINUX_STATE" ] && echo "0" > /selinux/enforce
		start rcS-emergency
		[ -n "$SELINUX_STATE" ] && echo "1" > /selinux/enforce
		[ -n "$PLYMOUTH" ] && plymouth --show-splash
	fi
	fsckoptions="$AUTOFSCK_OPT $fsckoptions"
fi

if [ "$BOOTUP" = "color" ]; then
	fsckoptions="-C $fsckoptions"
else
	fsckoptions="-V $fsckoptions"
fi

READONLY=
if [ -f /etc/sysconfig/readonly-root ]; then
	. /etc/sysconfig/readonly-root
fi
if strstr "$cmdline" readonlyroot ; then
	READONLY=yes
	[ -z "$RW_MOUNT" ] && RW_MOUNT=/var/lib/stateless/writable
	[ -z "$STATE_MOUNT" ] && STATE_MOUNT=/var/lib/stateless/state
fi
if strstr "$cmdline" noreadonlyroot ; then
	READONLY=no
fi

if [ "$READONLY" = "yes" -o "$TEMPORARY_STATE" = "yes" ]; then

	mount_empty() {
		if [ -e "$1" ]; then
			echo "$1" | cpio -p -vd "$RW_MOUNT" &>/dev/null
			mount -n --bind "$RW_MOUNT$1" "$1"
		fi
	}

	mount_dirs() {
		if [ -e "$1" ]; then
			mkdir -p "$RW_MOUNT$1"
			find "$1" -type d -print0 | cpio -p -0vd "$RW_MOUNT" &>/dev/null
			mount -n --bind "$RW_MOUNT$1" "$1"
		fi
	}

	mount_files() {
		if [ -e "$1" ]; then
			cp -a --parents "$1" "$RW_MOUNT"
			mount -n --bind "$RW_MOUNT$1" "$1"
		fi
	}

	# Common mount options for scratch space regardless of
	# type of backing store
	mountopts=

	# Scan partitions for local scratch storage
	rw_mount_dev=$(blkid -t LABEL="$RW_LABEL" -l -o device)

	# First try to mount scratch storage from /etc/fstab, then any
	# partition with the proper label.  If either succeeds, be sure
	# to wipe the scratch storage clean.  If both fail, then mount
	# scratch storage via tmpfs.
	if mount $mountopts "$RW_MOUNT" > /dev/null 2>&1 ; then
		rm -rf "$RW_MOUNT" > /dev/null 2>&1
	elif [ x$rw_mount_dev != x ] && mount $rw_mount_dev $mountopts "$RW_MOUNT" > /dev/null 2>&1; then
		rm -rf "$RW_MOUNT"  > /dev/null 2>&1
	else
		mount -n -t tmpfs $RW_OPTIONS $mountopts none "$RW_MOUNT"
	fi

	for file in /etc/rwtab /etc/rwtab.d/* /dev/.initramfs/rwtab ; do
		is_ignored_file "$file" && continue
	[ -f $file ] && cat $file | while read type path ; do
			case "$type" in
				empty)
					mount_empty $path
					;;
				files)
					mount_files $path
					;;
				dirs)
					mount_dirs $path
					;;
				*)
					;;
			esac
			[ -n "$SELINUX_STATE" -a -e "$path" ] && restorecon -R "$path"
		done
	done

	# Use any state passed by initramfs
	[ -d /dev/.initramfs/state ] && cp -a /dev/.initramfs/state/* $RW_MOUNT

	# In theory there should be no more than one network interface active
	# this early in the boot process -- the one we're booting from.
	# Use the network address to set the hostname of the client.  This
	# must be done even if we have local storage.
	ipaddr=
	if [ "$HOSTNAME" = "localhost" -o "$HOSTNAME" = "localhost.localdomain" ]; then
		ipaddr=$(ip addr show to 0.0.0.0/0 scope global | awk '/[[:space:]]inet / { print gensub("/.*","","g",$2) }')
		for ip in $ipaddr ; do
			HOSTNAME=
			eval $(ipcalc -h $ip 2>/dev/null)
			[ -n "$HOSTNAME" ] && { hostname ${HOSTNAME} ; break; }
		done
	fi
	
	# Clients with read-only root filesystems may be provided with a
	# place where they can place minimal amounts of persistent
	# state.  SSH keys or puppet certificates for example.
	#
	# Ideally we'll use puppet to manage the state directory and to
	# create the bind mounts.  However, until that's all ready this
	# is sufficient to build a working system.

	# First try to mount persistent data from /etc/fstab, then any
	# partition with the proper label, then fallback to NFS
	state_mount_dev=$(blkid -t LABEL="$STATE_LABEL" -l -o device)
	if mount $mountopts $STATE_OPTIONS "$STATE_MOUNT" > /dev/null 2>&1 ; then
		/bin/true
	elif [ x$state_mount_dev != x ] && mount $state_mount_dev $mountopts "$STATE_MOUNT" > /dev/null 2>&1;  then
		/bin/true
	elif [ ! -z "$CLIENTSTATE" ]; then
		# No local storage was found.  Make a final attempt to find
		# state on an NFS server.

		mount -t nfs $CLIENTSTATE/$HOSTNAME $STATE_MOUNT -o rw,nolock
	fi

	if [ -w "$STATE_MOUNT" ]; then

		mount_state() {
			if [ -e "$1" ]; then
				[ ! -e "$STATE_MOUNT$1" ] && cp -a --parents "$1" "$STATE_MOUNT"
				mount -n --bind "$STATE_MOUNT$1" "$1"
			fi
		}

		for file in /etc/statetab /etc/statetab.d/* ; do
			is_ignored_file "$file" && continue
			[ ! -f "$file" ] && continue

			if [ -f "$STATE_MOUNT/$file" ] ; then
				mount -n --bind "$STATE_MOUNT/$file" "$file"
			fi

			for path in $(grep -v "^#" "$file" 2>/dev/null); do
				mount_state "$path"
				[ -n "$SELINUX_STATE" -a -e "$path" ] && restorecon -R "$path"
			done
		done

		if [ -f "$STATE_MOUNT/files" ] ; then
			for path in $(grep -v "^#" "$STATE_MOUNT/files" 2>/dev/null); do
				mount_state "$path"
				[ -n "$SELINUX_STATE" -a -e "$path" ] && restorecon -R "$path"
			done
		fi
	fi

        if mount | grep -q /var/lib/nfs/rpc_pipefs ; then
                mount -t rpc_pipefs sunrpc /var/lib/nfs/rpc_pipefs && service rpcidmapd restart
        fi
fi

if [[ " $fsckoptions" != *" -y"* ]]; then
	fsckoptions="-a $fsckoptions"
fi

_RUN_QUOTACHECK=0
if [ -f /forcequotacheck ] || strstr "$cmdline" forcequotacheck ; then
	_RUN_QUOTACHECK=1
fi
if [ -z "$fastboot" -a "$READONLY" != "yes" ]; then

        STRING=$"Checking filesystems"
	echo $STRING
	fsck -T -t noopts=_netdev -A $fsckoptions
	rc=$?
	
	if [ "$rc" -eq "0" ]; then
		success "$STRING"
		echo
	elif [ "$rc" -eq "1" ]; then
	        passed "$STRING"
		echo
	elif [ "$rc" -eq "2" -o "$rc" -eq "3" ]; then
		echo $"Unmounting file systems"
		umount -a
		mount -n -o remount,ro /
		echo $"Automatic reboot in progress."
		reboot -f
        fi
	
        # A return of 4 or higher means there were serious problems.
	if [ $rc -gt 1 ]; then
		[ -n "$PLYMOUTH" ] && plymouth --hide-splash

		failure "$STRING"
		echo
		echo
		echo $"*** An error occurred during the file system check."
		echo $"*** Dropping you to a shell; the system will reboot"
		echo $"*** when you leave the shell."

                str=$"(Repair filesystem)"
		PS1="$str \# # "; export PS1
		[ "$SELINUX_STATE" = "1" ] && disable_selinux
		start rcS-emergency

		echo $"Unmounting file systems"
		umount -a
		mount -n -o remount,ro /
		echo $"Automatic reboot in progress."
		reboot -f
	elif [ "$rc" -eq "1" ]; then
		_RUN_QUOTACHECK=1
	fi
fi

remount_needed() {
  local state oldifs
  [ "$READONLY" = "yes" ] && return 1
  state=$(LC_ALL=C awk '/ \/ / && ($3 !~ /rootfs/) { print $4 }' /proc/mounts)
  oldifs=$IFS
  IFS=","
  for opt in $state ; do
	if [ "$opt" = "rw" ]; then
		IFS=$oldifs
		return 1
	fi
  done
  IFS=$oldifs
  return 0
}

# Remount the root filesystem read-write.
update_boot_stage RCmountfs
if remount_needed ; then
  action $"Remounting root filesystem in read-write mode: " mount -n -o remount,rw /
fi

# Clean up SELinux labels
if [ -n "$SELINUX_STATE" ]; then
   restorecon /etc/mtab /etc/ld.so.cache /etc/blkid/blkid.tab /etc/resolv.conf >/dev/null 2>&1
fi

# If relabeling, relabel mount points.
if [ -n "$SELINUX_STATE" -a "$READONLY" != "yes" ]; then
    if [ -f /.autorelabel ] || strstr "$cmdline" autorelabel ; then
	restorecon $(awk '!/^#/ && $4 !~ /noauto/ && $2 ~ /^\// { print $2 }' /etc/fstab) >/dev/null 2>&1
    fi
fi

if [ "$READONLY" != "yes" ] ; then
	# Clear mtab
	(> /etc/mtab) &> /dev/null

	# Remove stale backups
	rm -f /etc/mtab~ /etc/mtab~~

	# Enter mounted filesystems into /etc/mtab
	mount -f /
	mount -f /proc >/dev/null 2>&1
	mount -f /sys >/dev/null 2>&1
	mount -f /dev/pts >/dev/null 2>&1
	mount -f /dev/shm >/dev/null 2>&1
	mount -f /proc/bus/usb >/dev/null 2>&1
fi

# Mount all other filesystems (except for NFS and /proc, which is already
# mounted). Contrary to standard usage,
# filesystems are NOT unmounted in single user mode.
# The 'no' applies to all listed filesystem types. See mount(8).
if [ "$READONLY" != "yes" ] ; then
	action $"Mounting local filesystems: " mount -a -t nonfs,nfs4,smbfs,ncpfs,cifs,gfs,gfs2,glusterfs -O no_netdev
else
	action $"Mounting local filesystems: " mount -a -n -t nonfs,nfs4,smbfs,ncpfs,cifs,gfs,gfs2,glusterfs -O no_netdev
fi

# Check to see if a full relabel is needed
if [ -n "$SELINUX_STATE" -a "$READONLY" != "yes" ]; then
    if [ -f /.autorelabel ] || strstr "$cmdline" autorelabel ; then
	relabel_selinux
    fi
else
    if [ -d /etc/selinux -a "$READONLY" != "yes" ]; then
        [ -f /.autorelabel ] || touch /.autorelabel
    fi
fi

# Update quotas if necessary
if [ X"$_RUN_QUOTACHECK" = X1 -a -x /sbin/quotacheck ]; then
	action $"Checking local filesystem quotas: " /sbin/quotacheck -anug
fi

if [ -x /sbin/quotaon ]; then
    action $"Enabling local filesystem quotas: " /sbin/quotaon -aug
fi

# Initialize pseudo-random number generator
if [ -f "/var/lib/random-seed" ]; then
	cat /var/lib/random-seed > /dev/urandom
else
	[ "$READONLY" != "yes" ] && touch /var/lib/random-seed
fi
if [ "$READONLY" != "yes" ]; then
	chmod 600 /var/lib/random-seed
	dd if=/dev/urandom of=/var/lib/random-seed count=1 bs=4096 2>/dev/null
fi

if [ -f /etc/crypttab ]; then
    init_crypto 1
fi

# Configure machine if necessary.
if [ -f /.unconfigured ]; then

    if [ -x /bin/plymouth ]; then
        /bin/plymouth quit
    fi

    if [ -x /usr/bin/system-config-keyboard ]; then
	/usr/bin/system-config-keyboard
    fi
    if [ -x /usr/bin/passwd ]; then
        /usr/bin/passwd root
    fi
    if [ -x /usr/sbin/system-config-network-tui ]; then
	/usr/sbin/system-config-network-tui
    fi
    if [ -x /usr/sbin/timeconfig ]; then
	/usr/sbin/timeconfig
    fi
    if [ -x /usr/sbin/authconfig-tui ]; then
	/usr/sbin/authconfig-tui --nostart
    fi
    if [ -x /usr/sbin/ntsysv ]; then
	/usr/sbin/ntsysv --level 35
    fi

    # Reread in network configuration data.
    if [ -f /etc/sysconfig/network ]; then
	. /etc/sysconfig/network

	# Reset the hostname.
	action $"Resetting hostname ${HOSTNAME}: " hostname ${HOSTNAME}
    fi

    rm -f /.unconfigured
fi

# Clean out /.
rm -f /fastboot /fsckoptions /forcefsck /.autofsck /forcequotacheck /halt \
	/poweroff /.suspended &> /dev/null

# Do we need (w|u)tmpx files? We don't set them up, but the sysadmin might...
_NEED_XFILES=
[ -f /var/run/utmpx -o -f /var/log/wtmpx ] && _NEED_XFILES=1

# Clean up /var.
rm -rf /var/lock/cvs/* /var/run/screen/*
find /var/lock /var/run ! -type d -exec rm -f {} \;
rm -f /var/lib/rpm/__db* &> /dev/null
rm -f /var/gdm/.gdmfifo &> /dev/null

[ "$PROMPT" != no ] && plymouth watch-keystroke --command "touch /var/run/confirm" --keys=Ii &

# Clean up utmp/wtmp
> /var/run/utmp
touch /var/log/wtmp
chgrp utmp /var/run/utmp /var/log/wtmp
chmod 0664 /var/run/utmp /var/log/wtmp
if [ -n "$_NEED_XFILES" ]; then
  > /var/run/utmpx
  touch /var/log/wtmpx
  chgrp utmp /var/run/utmpx /var/log/wtmpx
  chmod 0664 /var/run/utmpx /var/log/wtmpx
fi
[ -n "$SELINUX_STATE" ] && restorecon /var/run/utmp* /var/log/wtmp* >/dev/null 2>&1

# Clean up various /tmp bits
[ -n "$SELINUX_STATE" ] && restorecon /tmp
rm -f /tmp/.X*-lock /tmp/.lock.* /tmp/.gdm_socket /tmp/.s.PGSQL.*
rm -rf /tmp/.X*-unix /tmp/.ICE-unix /tmp/.font-unix /tmp/hsperfdata_* \
       /tmp/kde-* /tmp/ksocket-* /tmp/mc-* /tmp/mcop-* /tmp/orbit-*  \
       /tmp/scrollkeeper-*  /tmp/ssh-* \
       /dev/.in_sysinit

# Make ICE directory
mkdir -m 1777 -p /tmp/.ICE-unix >/dev/null 2>&1
chown root:root /tmp/.ICE-unix
[ -n "$SELINUX_STATE" ] && restorecon /tmp/.ICE-unix >/dev/null 2>&1

# Start up swapping.
update_boot_stage RCswap
action $"Enabling /etc/fstab swaps: " swapon -a -e
if [ "$AUTOSWAP" = "yes" ]; then
	curswap=$(awk '/^\/dev/ { print $1 }' /proc/swaps | while read x; do get_numeric_dev dec $x ; echo -n " "; done)
	swappartitions=$(blkid -t TYPE=swap -o device)
	if [ x"$swappartitions" != x ]; then
		for partition in $swappartitions ; do
			[ ! -e $partition ] && continue
			majmin=$(get_numeric_dev dec $partition)
			echo $curswap | grep -qw "$majmin" || action $"Enabling local swap partitions: " swapon $partition
		done
	fi
fi

# Set up binfmt_misc
/bin/mount -t binfmt_misc none /proc/sys/fs/binfmt_misc > /dev/null 2>&1

# Boot time profiles. Yes, this should be somewhere else.
if [ -x /usr/sbin/system-config-network-cmd ]; then
  if strstr "$cmdline" netprofile= ; then
    for arg in $cmdline ; do
        if [ "${arg##netprofile=}" != "${arg}" ]; then
	    /usr/sbin/system-config-network-cmd --profile ${arg##netprofile=}
        fi
    done
  fi
fi

# Now that we have all of our basic modules loaded and the kernel going,
# let's dump the syslog ring somewhere so we can find it later
[ -f /var/log/dmesg ] && mv -f /var/log/dmesg /var/log/dmesg.old
dmesg -s 131072 > /var/log/dmesg

# create the crash indicator flag to warn on crashes, offer fsck with timeout
touch /.autofsck &> /dev/null

[ "$PROMPT" != no ] && plymouth --ignore-keystroke=Ii
if strstr "$cmdline" confirm ; then
	touch /var/run/confirm
fi

# Let rhgb know that we're leaving rc.sysinit
if [ -x /bin/plymouth ]; then
    /bin/plymouth --sysinit
fi

系统初始化脚本功能

(1) 设置主机名
(2) 设置欢迎信息
(3) 激活udev和selinux
(4) 挂载/etc/fstab文件中定义的文件系统
(5) 检测根文件系统，并以读写方式重新挂载根文件系统
(6) 设置系统时钟
(7) 激活swap设备
(8) 根据/etc/sysctl.conf文件设置内核参数
(9) 激活lvm及software raid设备
(10)加载额外设备的驱动程序
(11)清理操作

范例：

[root@centos6 ~]# cat /etc/init/rcS.conf
# rcS - runlevel compatibility
#
# This task runs the old sysv-rc startup scripts.
#
# Do not edit this file directly. If you want to change the behaviour,
# please create a file rcS.override and put your changes there.

start on startup

stop on runlevel

task

# Note: there can be no previous runlevel here, if we have one it's bad
# information (we enter rc1 not rcS for maintenance).  Run /etc/rc.d/rc
# without information so that it defaults to previous=N runlevel=S.
console output
pre-start script
	for t in $(cat /proc/cmdline); do
		case $t in
			emergency)
				start rcS-emergency
				break
			;;
		esac
	done
end script
exec /etc/rc.d/rc.sysinit
post-stop script
	if [ "$UPSTART_EVENTS" = "startup" ]; then
		[ -f /etc/inittab ] && runlevel=$(/bin/awk -F ':' '$3 == "initdefault" && $1 !~ "^#" { print $2 }' /etc/inittab)
		[ -z "$runlevel" ] && runlevel="3"
		for t in $(cat /proc/cmdline); do
			case $t in
				-s|single|S|s) runlevel="S" ;;
				[1-9])       runlevel="$t" ;;
			esac
		done
		exec telinit $runlevel
	fi
end script

1.3.5.3 服务管理

[root@centos6 ~]# cat /etc/init/rc.conf
# rc - System V runlevel compatibility
#
# This task runs the old sysv-rc runlevel scripts.  It
# is usually started by the telinit compatibility wrapper.
#
# Do not edit this file directly. If you want to change the behaviour,
# please create a file rc.override and put your changes there.

start on runlevel [0123456]

stop on runlevel [!$RUNLEVEL]

task

export RUNLEVEL
console output
exec /etc/rc.d/rc $RUNLEVEL

[root@centos6 ~]# file /etc/rc.d/rc
/etc/rc.d/rc: Bourne-Again shell script text executable
[root@centos6 ~]# cat /etc/rc.d/rc
#! /bin/bash
#
# rc            This file is responsible for starting/stopping
#               services when the runlevel changes.
#
# Original Author:       
#               Miquel van Smoorenburg, <miquels@drinkel.nl.mugnet.org>
#

set -m

# check a file to be a correct runlevel script
check_runlevel ()
{
	# Check if the file exists at all.
	[ -x "$1" ] || return 1
	is_ignored_file "$1" && return 1
	return 0
}

# Now find out what the current and what the previous runlevel are.
argv1="$1"		#根据这个$1参数运行
set $(/sbin/runlevel)
runlevel=$2
previous=$1
export runlevel previous

. /etc/init.d/functions

export CONSOLETYPE
do_confirm="no"
if [ -f /var/run/confirm ]; then
	do_confirm="yes"
fi
UPSTART=
[ -x /sbin/initctl ] && UPSTART=yes
# See if we want to be in user confirmation mode
if [ "$previous" = "N" ]; then
	if [ "$do_confirm" = "yes" ]; then
		echo $"Entering interactive startup"
	else
		echo $"Entering non-interactive startup"
	fi
fi

# Get first argument. Set new runlevel to this argument.
[ -n "$argv1" ] && runlevel="$argv1"

# Is there an rc directory for this new runlevel?
[ -d /etc/rc$runlevel.d ] || exit 0

# Set language, vc settings once to avoid doing it for every init script
# through functions
if [ -f /etc/sysconfig/i18n -a -z "${NOLOCALE:-}" ] ; then
  . /etc/profile.d/lang.sh 2>/dev/null
  export LANGSH_SOURCED=1
fi

# First, run the KILL scripts.		#先运行这段代码
for i in /etc/rc$runlevel.d/K* ; do

	# Check if the subsystem is already up.
	subsys=${i#/etc/rc$runlevel.d/K??}
	[ -f /var/lock/subsys/$subsys -o -f /var/lock/subsys/$subsys.init ] || continue
	check_runlevel "$i" || continue

	# Bring the subsystem down.
	[ -n "$UPSTART" ] && initctl emit --quiet stopping JOB=$subsys
	$i stop
	[ -n "$UPSTART" ] && initctl emit --quiet stopped JOB=$subsys
done

# Now run the START scripts.		#再运行这段代码
for i in /etc/rc$runlevel.d/S* ; do

	# Check if the subsystem is already up.
	subsys=${i#/etc/rc$runlevel.d/S??}
	[ -f /var/lock/subsys/$subsys ] && continue
	[ -f /var/lock/subsys/$subsys.init ] && continue
	check_runlevel "$i" || continue
		    
	# If we're in confirmation mode, get user confirmation
	if [ "$do_confirm" = "yes" ]; then
		confirm $subsys
		rc=$?
		if [ "$rc" = "1" ]; then
			continue
		elif [ "$rc" = "2" ]; then
			do_confirm="no"
		fi
	fi

	update_boot_stage "$subsys"
	# Bring the subsystem up.
	[ -n "$UPSTART" ] && initctl emit --quiet starting JOB=$subsys
	if [ "$subsys" = "halt" -o "$subsys" = "reboot" ]; then
		export LC_ALL=C
		exec $i start
	fi
	$i start
	[ -n "$UPSTART" ] && initctl emit --quiet started JOB=$subsys
done
[ "$do_confirm" = "yes" ] && rm -f /var/run/confirm
exit 0

[root@centos6 ~]# ls /etc/rc*.d -d
/etc/rc0.d  /etc/rc1.d  /etc/rc2.d  /etc/rc3.d  /etc/rc4.d  /etc/rc5.d  /etc/rc6.d  /etc/rc.d
[root@centos6 ~]# ls /etc/rc3.d
K10saslauthd  K87restorecond  K89rdisc  S08ip6tables  S10network  S12rsyslog    S25blk-availability  S26udev-post  S55sshd     S90crond
K61nfs-rdma   K89netconsole   S05rdma   S08iptables   S11auditd   S15mdmonitor  S25netfs             S50kdump      S80postfix  S99local

[root@centos6 ~]# ll /etc/rc.d/rc3.d
total 0
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 K10saslauthd -> ../init.d/saslauthd
lrwxrwxrwx. 1 root root 18 Oct  6 23:46 K61nfs-rdma -> ../init.d/nfs-rdma
lrwxrwxrwx. 1 root root 21 Oct  6 23:45 K87restorecond -> ../init.d/restorecond
lrwxrwxrwx. 1 root root 20 Oct  6 23:45 K89netconsole -> ../init.d/netconsole
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 K89rdisc -> ../init.d/rdisc
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 S05rdma -> ../init.d/rdma
lrwxrwxrwx. 1 root root 19 Oct  6 23:46 S08ip6tables -> ../init.d/ip6tables
lrwxrwxrwx. 1 root root 18 Oct  6 23:45 S08iptables -> ../init.d/iptables
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 S10network -> ../init.d/network
lrwxrwxrwx. 1 root root 16 Oct  6 23:46 S11auditd -> ../init.d/auditd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 S12rsyslog -> ../init.d/rsyslog
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 S15mdmonitor -> ../init.d/mdmonitor
lrwxrwxrwx. 1 root root 26 Oct  6 23:45 S25blk-availability -> ../init.d/blk-availability
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 S25netfs -> ../init.d/netfs
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 S26udev-post -> ../init.d/udev-post
lrwxrwxrwx. 1 root root 15 Oct  6 23:46 S50kdump -> ../init.d/kdump
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 S55sshd -> ../init.d/sshd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 S80postfix -> ../init.d/postfix
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 S90crond -> ../init.d/crond
lrwxrwxrwx. 1 root root 11 Oct  6 23:45 S99local -> ../rc.local

service 命令：手动管理服务

service 服务 start|stop|restart
service --status-all

/etc/rc.d/rc 控制服务脚本的开机自动运行

for srv in /etc/rc.d/rcN.d/K*; do
    $srv stop
done
for srv in /etc/rc.d/rcN.d/S*; do
    $srv start
done

说明：rc N --> 意味着读取/etc/rc.d/rcN.d/

K: K##：##运行次序；数字越小，越先运行；数字越小的服务，通常为依赖到别的服务

S: S##：##运行次序；数字越小，越先运行；数字越小的服务，通常为被依赖到的服务

配置服务开机启动

chkconfig命令
ntsysv命令

chkconfig 命令管理服务

#查看服务在所有级别的启动或关闭设定情形：
chkconfig [--list] [name]

#添加服务
SysV的服务脚本放置于/etc/rc.d/init.d (/etc/init.d)
#!/bin/bash
chkconfig: LLLL nn nn #LLLL 表示初始在哪个级别下启动，-表示都不启动
description : 描述信息

chkconfig --add name

#删除服务
chkconfig --del name

#修改指定的运行级别
chkconfig [--level levels] name <on|off|reset>

说明：--level LLLL: 指定要设置的级别；省略时表示2345

范例:

[root@centos6 ~]# service crond status
crond (pid  1358) is running...
[root@centos6 ~]# service rdisc status
rdisc is stopped

[root@centos6 ~]# chkconfig --list
auditd         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
blk-availability	0:off	1:on	2:on	3:on	4:on	5:on	6:off
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
ip6tables      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
iptables       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
kdump          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
mdmonitor      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
netconsole     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
netfs          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
network        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
nfs-rdma       	0:off	1:off	2:off	3:off	4:off	5:off	6:off
postfix        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rdisc          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rdma           	0:off	1:on	2:on	3:on	4:on	5:on	6:off
restorecond    	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rsyslog        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
saslauthd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sshd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
udev-post      	0:off	1:on	2:on	3:on	4:on	5:on	6:off

[root@centos6 ~]# chkconfig --level 2345 crond off
[root@centos6 ~]# chkconfig --list crond
crond          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
[root@centos6 ~]# ls /etc/rc*.d/*crond
/etc/rc0.d/K60crond  /etc/rc2.d/K60crond  /etc/rc4.d/K60crond  /etc/rc6.d/K60crond
/etc/rc1.d/K60crond  /etc/rc3.d/K60crond  /etc/rc5.d/K60crond

[root@centos6 ~]# chkconfig crond on
[root@centos6 ~]# chkconfig --list crond
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
[root@centos6 ~]# ls /etc/rc*.d/*crond
/etc/rc0.d/K60crond  /etc/rc2.d/S90crond  /etc/rc4.d/S90crond  /etc/rc6.d/K60crond
/etc/rc1.d/K60crond  /etc/rc3.d/S90crond  /etc/rc5.d/S90crond

[root@centos6 ~]# ls /etc/rc3.d/*
/etc/rc3.d/K10saslauthd    /etc/rc3.d/S05rdma       /etc/rc3.d/S12rsyslog           /etc/rc3.d/S50kdump    /etc/rc3.d/S99local
/etc/rc3.d/K61nfs-rdma     /etc/rc3.d/S08ip6tables  /etc/rc3.d/S15mdmonitor         /etc/rc3.d/S55sshd
/etc/rc3.d/K87restorecond  /etc/rc3.d/S08iptables   /etc/rc3.d/S25blk-availability  /etc/rc3.d/S56xinetd
/etc/rc3.d/K89netconsole   /etc/rc3.d/S10network    /etc/rc3.d/S25netfs             /etc/rc3.d/S80postfix
/etc/rc3.d/K89rdisc        /etc/rc3.d/S11auditd     /etc/rc3.d/S26udev-post         /etc/rc3.d/S90crond

[root@centos6 ~]# ls /etc/init.d
auditd            functions  iptables  mdmonitor   network   rdisc        rsyslog    single   udev-post
blk-availability  halt       kdump     netconsole  nfs-rdma  rdma         sandbox    sshd
crond             ip6tables  killall   netfs       postfix   restorecond  saslauthd  testsrv

[root@centos6 ~]# ls /etc/init.d/crond
/etc/init.d/crond

[root@centos6 ~]# cat /etc/init.d/crond
#!/bin/sh
#
# crond          Start/Stop the cron clock daemon.
#
# chkconfig: 2345 90 60
# description: cron is a standard UNIX program that runs user-specified \
#              programs at periodic scheduled times. vixie cron adds a \
#              number of features to the basic UNIX cron, including better \
#              security and more powerful configuration options.

### BEGIN INIT INFO
# Provides: crond crontab
# Required-Start: $local_fs $syslog
# Required-Stop: $local_fs $syslog
# Default-Start:  2345
# Default-Stop: 90
# Short-Description: run cron daemon
# Description: cron is a standard UNIX program that runs user-specified 
#              programs at periodic scheduled times. vixie cron adds a 
#              number of features to the basic UNIX cron, including better 
#              security and more powerful configuration options.
### END INIT INFO

[ -f /etc/sysconfig/crond ] || { 
    [ "$1" = "status" ] && exit 4 || exit 6 
}

RETVAL=0
prog="crond"
exec=/usr/sbin/crond
lockfile=/var/lock/subsys/crond
config=/etc/sysconfig/crond

# Source function library.
. /etc/rc.d/init.d/functions

[ $UID -eq 0 ] && [ -e /etc/sysconfig/$prog ] && . /etc/sysconfig/$prog

start() {
    if [ $UID -ne 0 ] ; then
        echo "User has insufficient privilege."
        exit 4
    fi
    [ -x $exec ] || exit 5
    [ -f $config ] || exit 6
    echo -n $"Starting $prog: "
    daemon $prog $CRONDARGS
    retval=$?
    echo
    [ $retval -eq 0 ] && touch $lockfile
}

stop() {
    if [ $UID -ne 0 ] ; then
        echo "User has insufficient privilege."
        exit 4
    fi
    echo -n $"Stopping $prog: "
	if [ -n "`pidfileofproc $exec`" ]; then
		killproc $exec
		RETVAL=3
	else
		failure $"Stopping $prog"
	fi
    retval=$?
    echo
    [ $retval -eq 0 ] && rm -f $lockfile
}

restart() {
    rh_status_q && stop
    start
}

reload() {
	echo -n $"Reloading $prog: "
	if [ -n "`pidfileofproc $exec`" ]; then
		killproc $exec -HUP
	else
		failure $"Reloading $prog"
	fi
	retval=$?
	echo
}

force_reload() {
	# new configuration takes effect after restart
    restart
}

rh_status() {
    # run checks to determine if the service is running or use generic status
    status -p /var/run/crond.pid $prog
}

rh_status_q() {
    rh_status >/dev/null 2>&1
}


case "$1" in
    start)
        rh_status_q && exit 0
        $1
        ;;
    stop)
        rh_status_q || exit 0
        $1
        ;;
    restart)
        $1
        ;;
    reload)
        rh_status_q || exit 7
        $1
        ;;
    force-reload)
        force_reload
        ;;
    status)
        rh_status
        ;;
    condrestart|try-restart)
        rh_status_q || exit 0
        restart
        ;;
    *)
        echo $"Usage: $0 {start|stop|status|restart|condrestart|try-restart|reload|force-reload}"
        exit 2
esac
exit $?

[root@centos6 ~]# ls /etc/rc3.d/*
/etc/rc3.d/K10saslauthd    /etc/rc3.d/K89rdisc      /etc/rc3.d/S10network    /etc/rc3.d/S25blk-availability  /etc/rc3.d/S55sshd
/etc/rc3.d/K61nfs-rdma     /etc/rc3.d/S05rdma       /etc/rc3.d/S11auditd     /etc/rc3.d/S25netfs             /etc/rc3.d/S80postfix
/etc/rc3.d/K87restorecond  /etc/rc3.d/S08ip6tables  /etc/rc3.d/S12rsyslog    /etc/rc3.d/S26udev-post         /etc/rc3.d/S90crond
/etc/rc3.d/K89netconsole   /etc/rc3.d/S08iptables   /etc/rc3.d/S15mdmonitor  /etc/rc3.d/S50kdump             /etc/rc3.d/S99local

[root@centos6 ~]# ll /etc/rc3.d/*
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc3.d/K10saslauthd -> ../init.d/saslauthd
lrwxrwxrwx. 1 root root 18 Oct  6 23:46 /etc/rc3.d/K61nfs-rdma -> ../init.d/nfs-rdma
lrwxrwxrwx. 1 root root 21 Oct  6 23:45 /etc/rc3.d/K87restorecond -> ../init.d/restorecond
lrwxrwxrwx. 1 root root 20 Oct  6 23:45 /etc/rc3.d/K89netconsole -> ../init.d/netconsole
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 /etc/rc3.d/K89rdisc -> ../init.d/rdisc
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 /etc/rc3.d/S05rdma -> ../init.d/rdma
lrwxrwxrwx. 1 root root 19 Oct  6 23:46 /etc/rc3.d/S08ip6tables -> ../init.d/ip6tables
lrwxrwxrwx. 1 root root 18 Oct  6 23:45 /etc/rc3.d/S08iptables -> ../init.d/iptables
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc3.d/S10network -> ../init.d/network
lrwxrwxrwx. 1 root root 16 Oct  6 23:46 /etc/rc3.d/S11auditd -> ../init.d/auditd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc3.d/S12rsyslog -> ../init.d/rsyslog
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc3.d/S15mdmonitor -> ../init.d/mdmonitor
lrwxrwxrwx. 1 root root 26 Oct  6 23:45 /etc/rc3.d/S25blk-availability -> ../init.d/blk-availability
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 /etc/rc3.d/S25netfs -> ../init.d/netfs
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc3.d/S26udev-post -> ../init.d/udev-post
lrwxrwxrwx. 1 root root 15 Oct  6 23:46 /etc/rc3.d/S50kdump -> ../init.d/kdump
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 /etc/rc3.d/S55sshd -> ../init.d/sshd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc3.d/S80postfix -> ../init.d/postfix
lrwxrwxrwx  1 root root 15 Nov  2 19:55 /etc/rc3.d/S90crond -> ../init.d/crond
lrwxrwxrwx. 1 root root 11 Oct  6 23:45 /etc/rc3.d/S99local -> ../rc.local

[root@centos6 ~]# ll /etc/rc5.d/*
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc5.d/K10saslauthd -> ../init.d/saslauthd
lrwxrwxrwx. 1 root root 18 Oct  6 23:46 /etc/rc5.d/K61nfs-rdma -> ../init.d/nfs-rdma
lrwxrwxrwx. 1 root root 21 Oct  6 23:45 /etc/rc5.d/K87restorecond -> ../init.d/restorecond
lrwxrwxrwx. 1 root root 20 Oct  6 23:45 /etc/rc5.d/K89netconsole -> ../init.d/netconsole
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 /etc/rc5.d/K89rdisc -> ../init.d/rdisc
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 /etc/rc5.d/S05rdma -> ../init.d/rdma
lrwxrwxrwx. 1 root root 19 Oct  6 23:46 /etc/rc5.d/S08ip6tables -> ../init.d/ip6tables
lrwxrwxrwx. 1 root root 18 Oct  6 23:45 /etc/rc5.d/S08iptables -> ../init.d/iptables
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc5.d/S10network -> ../init.d/network
lrwxrwxrwx. 1 root root 16 Oct  6 23:46 /etc/rc5.d/S11auditd -> ../init.d/auditd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc5.d/S12rsyslog -> ../init.d/rsyslog
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc5.d/S15mdmonitor -> ../init.d/mdmonitor
lrwxrwxrwx. 1 root root 26 Oct  6 23:45 /etc/rc5.d/S25blk-availability -> ../init.d/blk-availability
lrwxrwxrwx. 1 root root 15 Oct  6 23:45 /etc/rc5.d/S25netfs -> ../init.d/netfs
lrwxrwxrwx. 1 root root 19 Oct  6 23:45 /etc/rc5.d/S26udev-post -> ../init.d/udev-post
lrwxrwxrwx. 1 root root 15 Oct  6 23:46 /etc/rc5.d/S50kdump -> ../init.d/kdump
lrwxrwxrwx. 1 root root 14 Oct  6 23:46 /etc/rc5.d/S55sshd -> ../init.d/sshd
lrwxrwxrwx. 1 root root 17 Oct  6 23:45 /etc/rc5.d/S80postfix -> ../init.d/postfix
lrwxrwxrwx  1 root root 15 Nov  2 19:55 /etc/rc5.d/S90crond -> ../init.d/crond
lrwxrwxrwx. 1 root root 11 Oct  6 23:45 /etc/rc5.d/S99local -> ../rc.local

[root@centos6 ~]# ll /etc/rc.local
lrwxrwxrwx. 1 root root 13 Oct  6 23:45 /etc/rc.local -> rc.d/rc.local

[root@centos6 ~]#  cat /etc/rc.d/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

touch /var/lock/subsys/local
#/etc/rc.d/rc.local  开机启动文件写到这个文件里

[root@centos6 ~]# vim /etc/init.d/testsrv
#!/bin/bash
#chkconfig: - 96 3
#description: the service script

. /etc/init.d/functions
start(){
        touch /var/lock/subsys/testsrv
        action "Starting testsrv"
        sleep 3
} 
stop(){
        rm -f /var/lock/subsys/testsrv
        action "Shutting down testsrv"
}
restart(){
        stop
        start
}
status(){
        if [ -e /var/lock/subsys/testsrv ];then
            echo "testsrv is runing..."
        else
            echo "testsrv is stopped"
        fi
}

case $1 in
start)
    start
    ;;
stop)
    stop
    ;;
restart)
    restart
    ;;
status)
    status
    ;;
*)
    echo "Usage: /etc/init.d/testsrv {start|stop|restart|status}"
    ;; 
esac

[root@centos6 ~]# chmod +x /etc/init.d/testsrv
[root@centos6 ~]# chkconfig --list
auditd         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
blk-availability	0:off	1:on	2:on	3:on	4:on	5:on	6:off
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
ip6tables      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
iptables       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
kdump          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
mdmonitor      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
netconsole     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
netfs          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
network        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
nfs-rdma       	0:off	1:off	2:off	3:off	4:off	5:off	6:off
postfix        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rdisc          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rdma           	0:off	1:on	2:on	3:on	4:on	5:on	6:off
restorecond    	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rsyslog        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
saslauthd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sshd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
udev-post      	0:off	1:on	2:on	3:on	4:on	5:on	6:off

[root@centos6 ~]# ls /etc/rc*.d/*testsrv
ls: cannot access /etc/rc*.d/*testsrv: No such file or directory

[root@centos6 ~]# service testsrv status
testsrv is stopped
[root@centos6 ~]# service testsrv start
Starting testsrv                                           [  OK  ]
[root@centos6 ~]# chkconfig testsrv on
[root@centos6 ~]# chkconfig --list testsrv
testsrv        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
[root@centos6 ~]# ls /etc/rc*.d/*testsrv
/etc/rc2.d/S96testsrv  /etc/rc3.d/S96testsrv  /etc/rc4.d/S96testsrv  /etc/rc5.d/S96testsrv

[root@centos6 ~]# reboot

[root@centos6 ~]# service testsrv status
testsrv is runing...

范例：服务启动失败，故障恢复

[root@centos6 ~]# vim /etc/init.d/testsrv 
#!/bin/bash
#chkconfig: - 96 3
#description: the service script

. /etc/init.d/functions
start(){
        touch /var/lock/subsys/testsrv
        action "Starting testsrv"
        sleep 1000  #把等待时间改成1000，模拟服务不能正常启动                              
}

[root@centos6 ~]# reboot

在这里插入图片描述
如果服务卡住，启动不了

在这里插入图片描述
按a

在这里插入图片描述
进入单用户模式

在这里插入图片描述

# chkconfig --list testsrv
# chkconfig testsrv off
# init 3

[root@centos6 ~]# chkconfig --del testsrv #删除开机启动服务
[root@centos6 ~]# chkconfig --list testsrv
service testsrv supports chkconfig, but is not referenced in any runlevel (run 'chkconfig --add testsrv')
[root@centos6 ~]# ls /etc/rc*.d/*testsrv
ls: cannot access /etc/rc*.d/*testsrv: No such file or directory

1.3.5.4 非独立服务

服务分为独立服务和非独立服务

瞬态（Transient）服务被超级守护进程 xinetd 进程所管理，也称为非独立服务

进入的请求首先被xinetd代理

配置文件：

/etc/xinetd.conf
/etc/xinetd.d/<service>

用chkconfig控制非独立服务开机启动

示例：chkconfig tftp on

/etc/rc.d/rc.local

注意：正常级别下，最后启动一个服务S99local没有链接至/etc/rc.d/init.d一个服务脚本，而是指向了/etc/rc.d/rc.local脚本

不便或不需写为服务脚本放置于/etc/rc.d/init.d/目录，且又想开机时自动运行的命令，可直接放置于/etc/rc.d/rc.local文件中

/etc/rc.d/rc.local在指定运行级别脚本后运行

范例：

[root@centos6 ~]# yum -y install telnet-server

[root@centos6 ~]# chkconfig --list
auditd         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
blk-availability	0:off	1:on	2:on	3:on	4:on	5:on	6:off
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
ip6tables      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
iptables       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
kdump          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
mdmonitor      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
netconsole     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
netfs          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
network        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
nfs-rdma       	0:off	1:off	2:off	3:off	4:off	5:off	6:off
postfix        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rdisc          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rdma           	0:off	1:on	2:on	3:on	4:on	5:on	6:off
restorecond    	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rsyslog        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
saslauthd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sshd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
udev-post      	0:off	1:on	2:on	3:on	4:on	5:on	6:off
xinetd         	0:off	1:off	2:off	3:on	4:on	5:on	6:off

xinetd based services:
	chargen-dgram: 	off
	chargen-stream:	off
	daytime-dgram: 	off
	daytime-stream:	off
	discard-dgram: 	off
	discard-stream:	off
	echo-dgram:    	off
	echo-stream:   	off
	tcpmux-server: 	off
	telnet:        	off
	time-dgram:    	off
	time-stream:   	off

[root@centos6 ~]# service xinetd start
Starting xinetd:                                           [  OK  ]
[root@centos6 ~]# service xinetd status
xinetd (pid  1465) is running...

[root@centos6 ~]# chkconfig telnet on
[root@centos6 ~]# chkconfig --list
auditd         	0:off	1:off	2:on	3:on	4:on	5:on	6:off
blk-availability	0:off	1:on	2:on	3:on	4:on	5:on	6:off
crond          	0:off	1:off	2:on	3:on	4:on	5:on	6:off
ip6tables      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
iptables       	0:off	1:off	2:on	3:on	4:on	5:on	6:off
kdump          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
mdmonitor      	0:off	1:off	2:on	3:on	4:on	5:on	6:off
netconsole     	0:off	1:off	2:off	3:off	4:off	5:off	6:off
netfs          	0:off	1:off	2:off	3:on	4:on	5:on	6:off
network        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
nfs-rdma       	0:off	1:off	2:off	3:off	4:off	5:off	6:off
postfix        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
rdisc          	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rdma           	0:off	1:on	2:on	3:on	4:on	5:on	6:off
restorecond    	0:off	1:off	2:off	3:off	4:off	5:off	6:off
rsyslog        	0:off	1:off	2:on	3:on	4:on	5:on	6:off
saslauthd      	0:off	1:off	2:off	3:off	4:off	5:off	6:off
sshd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
udev-post      	0:off	1:on	2:on	3:on	4:on	5:on	6:off
xinetd         	0:off	1:off	2:off	3:on	4:on	5:on	6:off

xinetd based services:
	chargen-dgram: 	off
	chargen-stream:	off
	daytime-dgram: 	off
	daytime-stream:	off
	discard-dgram: 	off
	discard-stream:	off
	echo-dgram:    	off
	echo-stream:   	off
	tcpmux-server: 	off
	telnet:        	on
	time-dgram:    	off
	time-stream:   	off

[root@centos6 ~]# ss -ntl
State       Recv-Q Send-Q                                       Local Address:Port                                         Peer Address:Port 
LISTEN      0      128                                                     :::22                                                     :::*     
LISTEN      0      128                                                      *:22                                                      *:*     
LISTEN      0      64                                                      :::23                                                     :::*     
LISTEN      0      100                                                    ::1:25                                                     :::*     
LISTEN      0      100                                              127.0.0.1:25                                                      *:* 

[root@centos6 ~]#  ss -ntlp
State       Recv-Q Send-Q                                       Local Address:Port                                         Peer Address:Port 
LISTEN      0      128                                                     :::22                                                     :::*      users:(("sshd",1301,4))
LISTEN      0      128                                                      *:22                                                      *:*      users:(("sshd",1301,3))
LISTEN      0      64                                                      :::23                                                     :::*      users:(("xinetd",1465,5)) #telnet依赖xinetd启动
LISTEN      0      100                                                    ::1:25                                                     :::*      users:(("master",1380,13))
LISTEN      0      100                                              127.0.0.1:25                                                      *:*      users:(("master",1380,12))

[root@centos6 ~]# ps aux |grep telnet
root       1496  0.0  0.0 103320   884 pts/0    S+   16:46   0:00 grep telnet
#telnet服务没有启动

[root@rocky8 ~]# telnet 172.31.0.6
Trying 172.31.0.6...
Connected to 172.31.0.6.
Escape character is '^]'.
CentOS release 6.10 (Final)
Kernel 2.6.32-754.el6.x86_64 on an x86_64
centos6 login: 

[root@centos6 ~]# ps aux |grep telnet
root       1503  0.0  0.1  12528  1024 ?        Ss   16:47   0:00 in.telnetd: 172.31.1.8
root       1508  0.0  0.0 103320   884 pts/0    S+   16:48   0:00 grep telnet
#一但有人访问telnet服务，就自动启动服务

[root@centos6 ~]# lsof -i :23
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
xinetd    1465 root    5u  IPv6  10616      0t0  TCP *:telnet (LISTEN)
in.telnet 1503 root    0u  IPv4  11192      0t0  TCP 172.31.0.6:telnet->172.31.1.8:44944 (ESTABLISHED)
in.telnet 1503 root    1u  IPv4  11192      0t0  TCP 172.31.0.6:telnet->172.31.1.8:44944 (ESTABLISHED)
in.telnet 1503 root    2u  IPv4  11192      0t0  TCP 172.31.0.6:telnet->172.31.1.8:44944 (ESTABLISHED)

#断开telnet访问
[root@centos6 ~]# ps aux |grep telnet
root       1515  0.0  0.0 103320   884 pts/0    S+   16:49   0:00 grep telnet
#telnet服务被关闭

1.3.5.5 开机启动文件 rc.local

/etc/rc.d/rc.local

注意：正常级别下，最后启动一个服务S99local没有链接至/etc/rc.d/init.d一个服务脚本，而是指向了/etc/rc.d/rc.local脚本

不便或不需写为服务脚本放置于/etc/rc.d/init.d/目录，且又想开机时自动运行的命令，可直接放置于/etc/rc.d/rc.local文件中

/etc/rc.d/rc.local在指定运行级别脚本后运行

范例：

[root@rocky8 ~]# ll /etc/rc.local
lrwxrwxrwx. 1 root root 13 May 19 10:58 /etc/rc.local -> rc.d/rc.local

[root@centos8 ~]# vim /etc/rc.d/rc.local
ping 127.0.0.1

[root@rocky8 ~]# chmod +x /etc/rc.d/rc.local
[root@rocky8 ~]# reboot

[root@rocky8 ~]# ps aux |grep ping
root         847  0.0  0.3  32448  2428 ?        S    17:38   0:00 ping 127.0.0.1
root        1338  0.0  0.1  12136  1068 pts/1    R+   17:38   0:00 grep --color=auto ping

1.3.6 CentOS 启动过程总结

/sbin/init --> (/etc/inittab) --> 设置默认运行级别 --> 运行系统初始脚本/etc/rc.d/rc.sysinit、完成系统初始化 -->(关闭对应下需要关闭的服务)启动需要启动服务/etc/rc#.d/Sxxxx,/etc/rc.d/rc.local–> 设置登录终端

参看：http://s4.51cto.com/wyfs02/M02/87/20/wKiom1fVBELjXsvaAAUkuL83t2Q304.jpg

在这里插入图片描述

标签：off,CentOS,启动,--,etc,init,rc,fi,root
来源： https://blog.csdn.net/qq_25599925/article/details/121170990

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ICode9

52.第十二章 Linux启动和内核管理 -- CentOS 的启动管理(一)

第十二章 Linux启动和内核管理

内容概述

1.CentOS 6 的启动管理

1.1 Linux 组成

1.2 内核设计流派

1.3 CentOS 6 启动流程

1.3.1 CentOS 6 启动流程

1.3.2 硬件启动POST

1.3.3 启动加载器 bootloader

1.3.3.1 grub 功能和组成

1.3.3.2 CentOS 6 grub 安装

1.3.3.3 grub legacy 管理

1.3. 加载 kernel

1.3.5 init初始化

1.3.5.1 运行级别

1.3.5.2 初始化脚本 sysinit

1.3.5.3 服务管理

1.3.5.4 非独立服务

1.3.5.5 开机启动文件 rc.local

1.3.6 CentOS 启动过程总结