Centos Startup Process and running level

I. Startup Process

1. bios finds the mbr primary Boot Sector on the disk

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

Different hardware platforms have different firmware and are solidified on the main board by a software 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/BIOSstop +

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

Set instance: BIOS/CMOS clock hardware clock hwclock system-Software Clock date

Time error

Synchronize Hardware and Software Clock

Hwclock -- help

Hwclock -- hctosys

-- Set modification time

2. Go to the grub interface and select 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

2.6.18 2 indicates that the primary version number is 6 times. Version 18: The last version number is 6. The second version number is 6.

Ls/boot

3. Read the kernel File-/boot/vmlinuz -*

4. Read the init image file-/boot/initrd -*

5. init to read/etc/inittab

6. Read the startup level (id: 3: init default)

7. Read/etc/rc. d/rc. sysinit, complete clock setting, host name setting, and Partition Table mounting (/etc/fstab)

8. read/etc/rc. d/rc Script, which absorbs three levels, and then starts/etc/rc. services starting with S under d/rc3.d do not start services starting with K in this directory

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 link ln-s source file target file (shortcut in windows)

Hard link ln-source file target file

# Note that the source file is an absolute path.

Iv. Running level:

0 Shutdown

1 single user

2. nfs is not supported (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 the running level:

Runlevel

5. Default system partition:

1. Mount/dev/sda1 to/boot

2./dev/sda2volgroup00 (volume group) logvol00 (logical volume)

3. swap Partition

6. Partition mounting:

1. view the Mount table

Cat/etc/fstab

Hardware Partition Mount directory file system file attribute read Sequence

2. view the mounting result

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

Check the status of a service at different levels:

Chkconfig -- list httpd

Set the httpd service to on at level 3:

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