Linux Command Preliminary understanding

Knowledge Points:

1. Virtual Console :

After the system starts directly into the character working mode, the system provides multiple (default 6) virtual consoles. Each virtual Console can be used independently of one another.

You can use ALT+F1~ALT+F6 to switch between multiple virtual consoles.

2.operating level of Linux system

0-System shutdown Status

1-Single user working status for maintenance

2-Multi-user mode (NFS not started)

3-Multi-user mode, character interface

The system is unused and is left to the user's own definition

5-Multi-user mode, and run x Windows after system startup, give a graphical login window

6-All processes are terminated, restarted

View the current operating level of the system

#runlevel

Switching the Run level

#init [0123456]

Directory Structure of 3.Linux

/	The gateway to the Linux file system and the highest level directory
/bin	The commands required by the base system. Functions and/usr/bin are similar, the files in this directory are executable, the common user can use the command
/boot	Kernel and the files required to load the kernel. In general, the GRUB system Boot Manager is also located in this directory
/dev	Device file storage directory, such as terminal, disk, etc.
/etc	All system configuration Files
/home	Default storage directory for normal user home directory
/lib	directory where library files and kernel modules are stored
/media	The mount point of the plug-and-play storage device is created in this directory automatically, such as USB flash drive, Cdrom/dvd automatically mount, also will create a directory in this directory
/mnt	mount point directory for temporary file system
/opt	Storage directory for third-party software
/root	Home directory for Linux super User root
/sbin	Basic system maintenance commands that can only be used by super users
/srv	This directory holds data that needs to be extracted after some services are started
/tmp	Temp file directory
/usr	Store user information such as commands, help files, etc., using system commands and applications
/var	Store frequently changing data, such as logs, mails, etc.

A few special file systems

File system	Mount point	Description
Root	/	Linux system running base point, root file system cannot be uninstalled
Proc	/proc	provides interfaces for accessing system kernel data in a file system, for 2.4 and 2.6 cores
Sysfs	/sys	Provides an interface for accessing system kernel data in a file system, using the 2.6 kernel
Tmpfs	/dev /var/run /var/lock	The file system that the program uses when accessing shared memory resources
Usbfs	/proc/bus/usb	File system to use when accessing USB devices
Devpts	/dev/pts	The file system that the kernel uses to interact with pseudo terminals (remotely logged in)
Swap	Special file system used by the kernel, no mount point	Used to create virtual memory

4.Linux command

-Commands and parameters are case-sensitive

-The program can execute regardless of the extension

-You can use the TAB key to complete commands or paths

-When the instruction is too long, you can use the \ symbol to jump off, making the instruction continuous to the next line.

5. Common Command Introduction

PWD View current working directory

CD Replacement Directory

Usage CD [catalogue]

Symbol	Significance
.	Current working directory
..	Parent Directory
~	User home Directory
-	Last working directory

LS Display directory

Usage: ls [parameter] [directory name]

LS parameter:

-A: Displays all files, including hidden files (files starting with.)

-L: Display in long format

-T: Display by modified time

-R: Display directory and subordinate subdirectory structure (recursive)

-M: Output the file name horizontally, and make a separator with ",".

-S: Sort by file size

Blue: Directory

Green: Executable file

Red: Compress files

Light blue: Link file

Grey: Other Files

mkdir Creating a Directory

Usage: mkdir [parameter] {directory name}

RmDir Deleting a directory

Usage: rmdir [parameter]{directory name}

If the directory is empty, it is deleted directly, and if there is content in the directory, an error message will be generated and the directory cannot be deleted, but the remaining empty directories will continue to be deleted. Note that directories that include only one subdirectory are not empty.

RM Delete files and folders

Usage: RM [parameter]{file}

Parameters:

-R Delete Entire directory tree (recursive delete)

-F Delete without prompting, delete directly

Tree displays files and directory trees

Usage: Tree [parameter] {file}

Parameter:-A does not hide any entries that begin with the. Character

-D displays only directories that do not display files

-F Each file displays the path

-T sort by last modified time

-l n displays only n-level directories (n is numeric)

# # #我自己使用的CentOS 6.5 version, the system does not have the tree installed by default

# # #如果是提示没有找到命令的可以试试我用的命令

# # # Yum-y Install tree (in the case of a net) I test success

Touch creates an empty file and changes the timestamp

Usage: Touch [parameters] {file}

Parameter:-D change timestamp to defined value (after date, format: 20151027)

CP Copy Directory

Usage: CP [parameter] {source file ...} {Destination file}

Parameter:-R recursive Execution (can replicate directory tree)

MV Move or rename files

Usage: MV [parameter] {original file} {destination file} Move one or more files to the target file at the same time

6. Acura Command Man Help documentation

Path:/usr/share/man

Usage: man [parameter] [query name]

------------------------------

/Find

Q exit

--help Help

-H Help

Info command

Help command

Readme

7. Turn off the machine

Sync writes data to disk synchronously

shutdown [parameter] time [warning message]

-T sec: how many seconds to delay between sending out warning messages and deleting messages

-K: not a real shutdown but just a warning message to all users

-R: Restart immediately after shutdown

-H: Stop system after shutdown

Init 0

Restart: Reboot or INIT6

Pure Hand Knock Summary, may be able to use it later

Linux Command Preliminary understanding