Linux basic Commands

How to use the command

Shutdown--help

Shutdown--?

Man shutdown these three ways can be

Shutdown's wrong, he'll have a clue.

Which command does not know how to use, ask a man on it

Man is manual handbook, manual Hand, manual

Clear

Clear is the clear screen, Windows is CLS

CD Conversion Catalog

The conversion directory is a CD, just like under windows

CD/So it's up to the root of the directory, the forward slash is the root of the directory

Mkdir

Mkdir make dir Create a new directory, not a file

Rm

RM-RF most commonly used

RmDir Delete an empty directory, the directory cannot have anything underneath it.

RmDir Empty directory Name

Rm-r Directory name recursive this command always asks me

RM-RF Directory name Force don't ask me again. Most commonly used

RM-RF file names can also be deleted

Recursive regression, recursive remove removal

Touch

Create a file

Touch 1 File name 1, no suffix

Under Linux, the suffix name of the file is technically meaningless. But when it comes to naming a file, it's normal. For example, 3.txt is a text RT.exe is an executable program

List the contents of a file

Cat TAC Head Tail more

Cat 3.txt positive sequence starts from the first line

TAC 3.txt Reverse from the countdown to the first line

Head 3.txt head head-3 3.txt list first 3 rows head can take parameter-lines

Tail 3.txt tail tail-1 3.txt last line

More 3.txt-------The default is to be paged, so a lot of plumbing used him

Cp+move

CP copy copy MV move mobile

CP 1 2 Copy 1 of this file, called 2, so I have two files.

Cp-r d1 D2 Copy directory must have parameter R

It is easy to understand: Delete a directory, the first thing to delete the directory below. To use recursion, the copy is also

MV D2 D1 Move D2 directory to D1, if not, add recursion mv–r

Name of the word MV

In addition to the MV can be moved outside, but also can change the name

Mv 3.txt 4.txt Change the name of 3.txt to 4.txt

Shutdown + Restart + exit

Exit is the QUIT command line

Reboot is a reboot.

Shutdown shutdown, this command needs to take a parameter shutdown now

The init 0 is also off because there are several layers, 6 floors.

Logout is logoff

Exit: Q--CTRL + c---ctrl+d, I don't know what they're quitting, try it all

Man LS when there will be a lot of content, Q key can exit

LS lists things under the directory

Under Windows is dir, and Dir is also available under Linux

List the contents of the current directory (including directories and files), this command has several parameters.

Ls–l this most commonly used

ls horizontal display, this line is full of the next line

Ls-l is an L, which is also a line display, but a single line displays only one file or directory, with detailed information about the file or directory.

Ls-m Horizontal row, this line is full of the next line

Ls-r a little like a tree show.

WhoAmI

Displays the current user, root or other user

Pwd

Displays the current directory you are in

Press 5 down ESC

Press 5 to ESC and there will be a lot of commands to use

Display all 2091 possiblities, so Redhat Linux has more than 2000 commands.

Mount Mount + Uninstall

Mount point mount Points

Mount----------------------------------------------------------------------

MOUNT/DEV/CDROM/MNT/CDR the CDROM device under the Dev directory under the root directory with the

The CDR directory under the MNT directory under the root directory is associated with this is the Mount

mount point------CDR device-----CDROM

Uninstall---------------------------------------------------------------------

Umount/dev/cdrom or UMOUNT/MNT/CDR

VI is important

This command interview most, VI is a text editor, similar to the Notepad of Windows

Touch is to create a file, but this file has no content, how to add content, with VI

VI 3.txt After finishing this command,

Out a text editor, but not the content, because just started to enter the command mode, can only knock command

VI has two modes-command mode and edit mode, just start to enter the command mode, cannot enter content

Hit a into the edit mode, the bottom will appear insert this word append append

Tap ESC to exit Edit mode and enter command mode

Under command mode, break the colon: and then the colon will appear underneath, and then the command W is disk

Q is to exit q! is not to save the WQ is to save the exit (most commonly used)

I think Wq is to save the exit W is not write meaning

More 3.txt displaying 3. txt content

Find

How does he differentiate with grep?

Find the name of a file (if you remember the approximate name), find its path path, where he

Find features are powerful

You can also find rc.local based on creation date.

Find/-name *local starting from the root directory, specifying a location, starting from there

Find/etc-name *local

find/etc | grep Local System go back to find all the files or directories that contain the local letters

Find/-name MySQL system just go back to the file or directory named MySQL.

Find/-name mysql* system go back to find the first few letters are MySQL (back any)

The file or directory

Names don't have to be written full

Whereis

Whereis ls find ls where is this command

/bin bin directory below are various commands VI cat LS pwd and so on

There are also various commands under the/usr/bin directory

View environment variables

See Environment variables under DOS

Echo%path%

Echo%classpath%

Under Linux echo $PATH PATH must be capitalized

Link Ln

is LN-------------link

ln 3.txt 4 More 4

What is the difference between a link and a copy----------for the link, I changed the 3.txt,4 content will automatically follow the change

If you haven't modified it 4

ln 3.txt 4 This is a hard link, which is equivalent to copying another copy, and then creating a shortcut between the two files

Modifying the 3.txt,4 will also change

Ln-s 3.txt 5 Soft This is a soft connection, equivalent to a shortcut inside windows

Soft Connect: Modify 3.txt,5 will also change

Differences between the two types of links

The 3.txt is deleted, 5 does not exist, the connection is broken, and 4 is present.

Wc

Word count is not a toilet wc-l lines how many lines this file has

Grep

grep is a very common command, please remember him firmly what his full name is

Global Regular Expressions Print Universal Regular expression version

Finds the specified string in a text file, and displays the line that contains it, paying attention to the line

grep Student 4

In 4 This text file to find student this string, which line contains it, displayed

^ in regular expressions, represents the beginning of a line

Ls-l | grep ' ^d ' only lists the directories,/etc files and directories are many

^ This character is above the number 6

Rpm–qa to list all the bags,

Rpm-qa | grep MySQL finds all the packages that contain the words MySQL, as long as the package name contains MySQL letters, it will be found

grep and find

Find/-name mysql*

Find/| grep MySQL

Fdisk-l L

Displays the current disk information

Dmesg

List boot information for power on the full name is------D message

DMESG | grep eth0 See the first NIC booting up normal?

Command Replacement Wall

command to replace---with no more open two command lines

Wall Full name------warning All notify everyone, warning everyone, not the wall

Wall HelloWorld

The wall ' date ' warning character is the current time, take date as a command, and warn the result of the command execution.

Wall Date warning character is date

' This character is the number 1 left that character

redirect

There's not much to redirect---

One of Java's original programs

Replace out the Out

SYSTEM.OUT.PRINTLN () The command is output to the command line, and now he outputs the command to the file.

Ls

ls > Cmd.txt Input the results of the command just executed by LS into the Cmd.txt file.

Error output redirection---------

Lssss > Cmd.txt No, lsss, this command doesn't exist.

Lssss 2> Cmd.txt

REDIRECT Input

Wall < Cmd.txt to warn the contents of Cmd.txt

The empty

Pipeline

Huge number of pipes

page display,/etc a lot of content below

Ls-r

Ls-r | More of the meaning of the sentence

Give the result of the last command to the next command

Ls-l/etc | More

| ----------------is a pipe connector

More The default is to be paged, but the ls-l will not be paged, sometimes the content of the display is huge, with more will result. It's not good to split pages.

Once the pipeline learns, his function will be very powerful.

Ls-l | grep ' ^d ' only lists the directories,/etc files and directories are many

File Permissions Files Privilege

The most important thing about Linux-file permissions------must master-----------files privilege

Objective

A total of 10 people on the left

-(on behalf of the file) d (for the directory) L (is the L for the link)

The leftmost one is removed, leaving 9, which can be divided into 3 groups.

-rw-r--r--divided into 3 groups-rw-r--r--

Drwxr-xr-x

lrwxrwxrwx

In addition to the representative characters, there are 9 digits, what they represent

The permissions for Linux files are divided into 4 types---------

Read Write Execute none (Nothing)

9 bits divided into 3 groups

The first group represents what permissions the owner of this file has

The second set of permissions that are owned by the same group as the owner of the file

The third group represents what the rest of the people have right

X--------------Execute

R-------------Read

W---------------Write

-Stands for nothing but none

Chmod-not Professional

You can also modify the permissions change mode changes Modify

chmod +x 4 to 4 This file plus executable permissions, then the three groups of people have this permission

Chmod-x 4 Canceling permissions

I want to give myself only to add executable permission, the remaining two groups of people I don't care, only to the first group plus permissions

chmod u+x 4

How to get this permission for other people in the same group chmod g+x 4, only add permission group to the second group

chmod o+x 4, add permissions to the third group only

Professional Modification method

The above wording is not professional, the following good---------------------

chmod 755 4 chmod 777 4

7 means that the permissions are all 5 means no write permission

Representation of permissions within Linux (Unix), represented by 3 octal numbers

000 =====0 111 ======7

Read and write executable

One 8 binary one 8 binary one 8 binary

Three-bit three-bit three-bit

How to modify the owner of a file

Chown TestUser1 4-------------Change owner

Management of simple users

When a user logs in, the default path is the user's home directory

Add user

Useradd testuser adduser testuser

Both of these can be

Set Password

passwd testuser to this user set the password, if you lose the wrong password, press the BACKSPACE key---no, no. Because the password does not appear

Two position changes

After adding a user, the system has two positions that change--------------/home and/etc

--------------------------------------1

Cd/home ls

The home directory will have an automatically generated directory called TestUser.

--------------------------------------2

What about the ETC catalogue?

Cd/etc

More passwd open passwd this file

passwd This file does not have a password, it is stored by all users, testuser This user can also be found here

Testuser:x:501:502::/home/testuser:/bin/bash

This User ID number---501 in the group: 502

The user's home directory is----/home/testuser

The shell--------used by this user/bin/bash

User Group------------------------------------------------

The group's information is/etc/group in this file

When you add a user who does not specify a group, he adds a group that is the same as your user name

Add a group

Groupadd TESTG

Useradd testuser2-g Testg Specify a group when adding users

You can also modify the group that the user belongs to Usermod-g testuser TestUser2

New group user name

Usermod---------User Modify

Delete Users and Groups

Delete users in two steps---Delete the user deleted his directory

Userdel TestUser

Cd/home

RM-RF TestUser

Deletion of groups

Groupdel TESTG

User Switching

Switch User

Su TestUser2

Shell

User's Shell---------

You're not dealing directly with the kernel.

There is a layer outside the kernel, called Shell,shell, that will explain the commands you hit under Linux, and then deal with the kernel.

The shell has different forms

There are different shell,c shells-------the C-language form of the shell

Different shell commands are not the same, the same commands are not common under different shells, common commands

Can be universal

We use the shell called Bash, the former name BSH, the origin of the name, is a person called bone

wrote, so called BSH, and later he wrote one side, bone again shell, so called bash

BASH------Switch to bash

CSH---switch to C shell

Ksh-----switch to K shell

The most primitive and primitive shell of SH

BSH------Switch to BSH

To modify the system default boot level

When modifying that profile, first back up

Modify the configuration file/etc/inittab, change the number in Id:5:initdefault 5 to 3

Because

3 Pure command line interface, with network sharing

5 graphical interface

The next time the system starts, it's not going to get into that graphical interface.

Important A few

Ip

View IP address and set IP address

Ifconfig can either query IP or set IP

Ipconfig is the command under Windows

Linux Query IP command ifconfig----------------

The ifconfig command can also configure IP----------

Ifconfig eth0 IP Address

Services Service

Start a service, such as a service that starts MySQL

Service MySQL start not all the commands have this d this letter

Service iptables Stop shutting down the firewall

Service VSFTPD start VSFTP server

Service VSFTPD Stop Service stopped

Service VSFTPD Restart Restart

But how do you know the name of the service?? Use this command chkconfig

Ps-ef

How to know that the service has been started, such as the MySQL service has been started

PS---process processes-e = =-A Lists all processes

Ps-ef | grep Service Name

Ps-ef | grep MySQL Ps-ef | grep Tomcat

There are questions (you can think of them as closed when the result is only one line)

Boot from Boot

You don't have to start mysql,vsftp,apache manually, and so on.

With Chkconfig This command, check configure checks the configuration

You can not only know if the service is booting.

You can also set up boot-up for this service

You can also know the name of the service.

How do I know the name of the service------------

Chkconfig--list This command will list all the service items, you can take a slow look, and you can search

Chkconfig--list | More

Chkconfig--list | grep MySQL

Chkconfig--list | grep vsftpd

Chkconfig MySQL on these several 3 4 5 levels all started

Chkconfig--level 3 MySQL on just starting at 3 this level

Chkconfig MySQL off

MySQL database service--------------MySQL

Vsftp Server service------------VSFTPD

Firewall service------------iptables

SSH service------------sshd

HTTP------------------httpd

Linux basic Commands