Linux study notes [02]

This is my university notes Mu class, specific video click here

Item 2 preliminary examination Shell

2.1 Shell Overview

1.Shell is between the user and the operating system kernel ( Kernel an interface) between; Linux command line is
2.Shell

• Bourne Shell（/bin/sh，/bin/bash）
• C Shell（/bin/csh，/bin/tcsh）
• Korn Shell

3.Bash: including early Bourne Shell and Korn Shell all functions, and some of the features added to the C Shell ( which is the default operating system, various Linux Shell )
4. The method of using the Shell

• graphic interface
  • Terminal window
  • Virtual Terminal (opening: Ctrl + Alt + F2 or Ctrl + Alt + F6, Returns: Ctrl + Alt + F1)
• Text interface

5. The front terminal content - [SJH the root-COM @ ~] #

• Currently logged on user name is root
• Host named sjh-com
• The current directory is ~ ( home directory )
• # Is the prompt ( super user, if it is $ prompt, compared with the average user )

6. The handover command account: su
Syntax: su [-] [username]
SU is equivalent to the root SU
SU SJH
extension: - action option

2.2 file and directory management command

Command List

• Copying files: cp
  • Format: cp [-fir] source file destination
  • -f represents a direct coverage
  • -i represents the views of users (Y / n-)
    CP / etc / password / tmp
    CP -R & lt / etc / yum / tmp
• Move files: mv
  • Format: mv [-fi] source file destination
    mv / tmp / yum / etc
    mv * .c / Home / SJH
    mv test.txt test2.txt
• Delete files or directories: rm
  • Command Format: rm [-f -i -r] file or directory name
    RM / tmp / *
    RM -rf / tmp / *
• Lists files and directories: ls
  • Format: ls [-lida] [filename or directory name]
    LS
    LS the -l
    LS -a / root
    LS -dil / root
• Create a directory: mkdir
  • Syntax: mkdir [-p] directory name
    mkdir ~ / Tools
    mkdir -p zzti / CS / WL15
• To delete a directory: rmdir
  • Format: rmdir [-p] directory name
    rmdir -p zzti / cs / wl15
• View the current working directory: pwd
• Change directory: cd
  • Syntax: cd [pathname]
    CD
    CD ~
    CD ..
    CD -
    CD /
    CD / Boot / GRUB
• View files and directories: find, locate
• View file types: file
  • Format: file filename
    File / bin / LS
    File / etc / passwd

2.3 Linux operating level

1. Run level ( runlevel ): operating system currently running functional level, defined in the / etc / inittab file
seven kinds of run level 2.Linux

0 halt shutdown, shutdown state represents the system
1 Single user mode single-user mode, supports only the root account
2 Multiuser, without NFS network file system does not support multi-user mode
3 Full Multiuser mode complete multi-user mode
4 unused system is not used, as reserved
5 X11 graphical multi-user mode
6 reboot to restart

3. The different operating levels may be switched with each other, and essentially no difference in the level of functional

Complement: If you lose the password for the root account, allowing the machine to boot into single-user mode, and then use the passwd command to reset the root password

4. Run level Principle

There are many /ect/rc.d/init.d in the directory server scripts, commonly referred to as Service ( Service )
has named seven rcN.d in /etc/rc.d ( N the range of 0 to 6 ) directories, 7 run level corresponding to the system
under rcN.d directory are some of the symbolic link files that point to service script files in the init.d directory, file naming these links to K + nn + service name or S + nn + service name, where nn is a two-digit number
will enter the corresponding rcN.d directory system according to the specified run level and follow the links to files in order to retrieve the file name directory: for with K ( Kill beginning of the file), the system the termination of the corresponding service; respect to S ( the start file) at the beginning, the system will start the corresponding service

The run level related operations

• View run level: runlevel
• Other operating level: the init N ( N is a value of 0123456 )

Set to run in command-level 6.CentOS7.3

• Checking runlevels: systemctl get-default
• Modified to run level 3: systemctl set-default multi-user.target
• Modified to run level 5: systemctl set-default graphical.target

2.4 Linux under common shortcuts

Details are as follows

command	Features
Tab	Command Completion
	File name or path completion
	Continuously press the Tab key twice, the display begins with the characters you have entered all the commands, file name or path
Ctrl+D	Exit terminal
	As in edit mode, then exit edit mode
	Delete from the cursor to the right
Ctrl+C	The end of the currently executing command
	Cancel edit the current command line
Ctrl+L	Terminal cleared
Ctrl+Z	The running program to the background
Ctrl+R	Search-history
Ctrl+A	Move the cursor to the first row of the line
Ctrl+E	Move the cursor to the end of the line where the line
Ctrl+U	Entered an incorrect command, use the shortcut key will erase the entire contents from the current cursor position to the beginning of the line
Ctrl+K	Entered an incorrect command, use the shortcut key will erase the entire contents from the current cursor position to the end of the line
Ctrl+W	Erase the word before the cursor position; if the cursor on a word itself, it will erase all of the letters of the first word from the cursor position to the word
Ctrl+Y	Paste using Ctrl + W, Ctrl + U and Ctrl + K shortcut erased text

Unfinished, continued ~