Centos startup process and running level

I. startup process 1. bios finds the mbr master boot sector firmware on the disk. fireware (CMOS/BIOS) checks whether the hardware is normal at the hardware level. different hardware platforms have different firmware, A piece of software Control Program (F2/delete/F10) CMOS on the motherboard is a piece of software that is solidified on the motherboard, while BIOS is a control field such as operating CMOS.

I,Startup Process

 

1.BiosFindMbrPrimary boot sector

 

The firmware fireware (CMOS/BIOS) checks whether the hardware is normal at the hardware level.

Different hardware platforms have different firmware,Solidified on the motherboardSectionSoftware Control Program(F2/delete/F10)

CMOS is the program that is solidified on the motherboard, while BIOS is the control interface such as operating CMOS.

Sum is not called CMOS/BIOS stop +

Common settings: security settings, bootable media list, bootable media search sequence, power management, and startup details

Set instance: BIOS/CMOS clock hardware clockHwclockSystem-software clockDate

Time error

Synchronize hardware and software clock

Hwclock -- help

Hwclock -- hctosys

-- Set modification time

 

 

2.EnterGrubSelect the corresponding startup Kernel

 

MBR Master boot record)

{Bootloader user-initiated program, Partition table disk Partition table, Magic Number ending flag}

Bootloader windows (ntldr)

/Etc/grub. conf

The most important role: Start the kernel

Vmlinuz-2.6.18-194.e15 executable file z decompression process

2.6.182Indicates the main version number.6Minor version number18Last version, second-digit 6, important odd-number test, even-digit official version

Ls/boot

 

 

3.ReadKernelKernel file-/Boot/vmlinuz -*

4.ReadInitImage file-/Boot/initrd -*

5.InitRead/Etc/inittab

6.Read startup level(Id: 3: init default)

7.Read/Etc/rc. d/rc. sysinit,Set the clock, host name, and partition table.(/Etc/fstab)

 

8.Read/Etc/rc. d/rcScript.3Level, and then start/Etc/rc. d/rc3.dRelatedSServices starting,Do not startKServices starting

 

9.Enter the logon page

 

2. modify the software clock

View system Time:

Date "+ % Y-% m-% d % H: % M: % S"

Modify software clock

Date-s "15:31:30"

 

Character page flip:

Shift + pgup | pgdn

 

View process:

Ps-ef | grep httpd

View Port:

Netstat-tunpl | grep: 80

 

3. create a link document (review):

Soft linkLn-s source file target File (shortcut in windows)

Hard linkLn-target file of the source file

 

#Note that the source file is an absolute path.

 

 

IV. operation level:

0 Shutdown

1 Single User

2 Not supportedNfs (Network File System)

3 Character interface

4 Not used

5 Graphic Interface

6 Restart

 

Change the system running level:

Init 0 | 3 | 5 | 6

 

View running level:

Runlevel

5. default system partition:

1. Mount/dev/sda1 to/boot

2./dev/sda2 volgroup00 (volume group) logvol00 (logical volume)

3. swap partition

VI. partition mounting:

 

1.View Mount table

Cat/etc/fstab

Hardware partition Mount directory file system file attribute read sequence

2.View results after mounting

Df? H

#-H converts k into m and g.

 

Host Name settings:

1. view the host name

Hostname

2. modify the host name

Hostname server

3. [root @ localhost basename] command prompt

 

 

View the status of a service at different levels:

Chkconfig -- list httpd

 

SetHttpdThe service isOn:

Chkconfig -- level 3 httpd on

 

Send:

Backup required:

1./etc/

2./boot/

3. website

 

Copy command:

1. ls-a: View all files, including hidden files

2. files starting with. in linux are hidden files.

 

Vi/boot/grub. conf

Default = 0

# The first system started by default