Getting started with Linux

1 Preface

My main course is Ubuntu, Embedded Linux in Silicon Valley

/video/BV1JF4m1A7mN/?spm_id_from=333.&vd_source=8e232ecca082f1beea092de8718f15c6

Why choose ubuntu? 1Ubuntu's graphical interface is good, 2Centos has also been discontinued

Recommend two tutorials

/linux/

https:///linux/

/as604049322/article/details/120446586?ops_request_misc=%257B%2522request%255Fid%2522%253A%252254215bdd3651060e91452003a21a521f%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=54215bdd3651060e91452003a21a521f&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_alltop_positive~default-1-120446586-null-null.142^v102pc_search_result_base3&utm_term=Linux&spm=1018.2226.3001.4187

blog

The tutorial has a focus and is not necessarily comprehensive. If you cannot solve it, you can check other ones.

Three websites help us learn

1 bean bun/chat/1856257831091970

Just ask him directly if you have no orders

2 Linux command manual query collection/

3utools /Install Linux documentation plug-in, you can query commands that do not know how to do so.

2 Environmental preparation

Resource download

I'm using VMware+unbantu

1 Download the VMware virtual machine

/group/ecx/productdownloads?subfamily=VMware Workstation Pro&freeDownloads=true

Downloading this thing is not easy

2 Download the unbantu image file

Tsinghua Source

/ubuntu-releases/22.04/

The suffix is ​​4.4G size

Alibaba Yuan

/mirror/ubuntu?spm=a2c6h.13651102.0.0.3e221b11rhacGu

Install

Installing VMware step by step is a fool's operation. You can refer to this document

/Mylilizhi/article/details/142969657

Creating a virtual machine is also a fool's operation. Please refer to this document

/xxjc2025/article/details/145669621

1 The disk size can reach 50G

2 Select NAT mode for network links

After installation, you can download Chinese

/linuxChinese input method

This happens when you open VMware again

Solution Right-click stand-alone software to run using the system administrator

ctrl + alt key Your mouse button will appear in the virtual machine

3 Commands

Linux all files

cd / move to root directory ls view all file directories

Linux Directory

1 Everything is a document

bin storage command (before storing binary files)

boot core image configuration file

cdrom CD drive file

dev device CPU disk network, etc.

erv environment configuration

home directory used by the user

lib dependency

media audio file

mnt temporary stored file

opt installation software

proc memory

root administrator

run

sbin advanced command system running

snap system snapshot

srv system run storage file var storage system run log tmp storage temporary files

sys operating system file

usr user public

Commonly used commands

sudo improves the permissions of commands

cd move directory cd .. Move to previous directory cd / move to root directory ./ is the current directory

~ number represents home directory home directory tab key fills hostname View hostname Uname -a View system command

mkdir Create directory ls View directory ls -alView all directories pwd displays the current working directory

touch Create empty file cp Copy file -- help history View history command

ps -aux Show process kill -9 Process number kills process cat View file

dpkg -i install the deb package tar -zxvf decompress file.gz --help help command

vim default viewing mode i insert mode esc command mode :wq Exit save! Enforcement

1 Basic command

3.1.1 Firewall

Port 22 is open by default

NetworkManagerNetwork Services*

systemctl start I stop I restart I status Service name

​ Start Stop Restart View

View the file list in /usr/lib/systemd/system directory. Each file corresponds to a service.

disable automatically starts

systemctl list-unit-files (Function description: Check the service startup status)

systemctl disable service_name (Function description: Turn off the automatic start of the specified service)

systemctl enable service_name (Function description: enable automatic start of the specified service)

ufw firewall

(1) Check the firewall status sudo systemctl status ufw

(2) Temporarily close the firewall sudo systemctl stop ufw

Turn off the firewall when powering on

(1) Set the firewall to start when powering on sudo systemctl enable ufw

(2) Set the firewall to turn off when powering on sudo systemctl disable ufw

(3) Check whether the service is powered on and started automatically. sudo systemctl is-enabled ufw

disabled means that the power is not enabled. enabled means that the power is not enabled.

3.1.2 Package Manager

Unbantu uses APT (Advanced Packaging Tools) which is a software package manager for Debian and its derived Linux. It can automatically download, configure, and install software packages in binary or source code formats, thus simplifying the process of managing software on Unix systems.

Common APT commands: Usage: apt [Options] Command Command Line Package Manager apt provides package search, management, and information query functions.

Enter apt to view the promotion command

list - List packages by name

search - Search package description

show - Show package details

install - Install the package

reinstall - reinstall package

remove - Remove package

autoremove - Uninstall all packages that are automatically installed and no longer used

update - Update the list of available packages

upgrade - Update the system through installation/upgrade software

full-upgrade - Update the system by uninstall/install/upgrade

edit-sources - Edit software source information file

satisfied - enables the system to satisfy dependency strings

Install dpkg

• i: Install the software package;
  -r: Delete the package;
  -P: Delete the software package while deleting its configuration file;
  -L: The file displayed in the software package associated;
  -l: Display the installed package list;
  --unpack: unpack the software package;
  -c: Display the list of files in the software package;
  --confiugre: Configure the package.

Install, create and manage software packages on Debian Linux systems

sudo dpkg -i jdk-21_linux-x64_bin.deb

3.1.3 Others

Shut down and restart

reboot (Function description: restart, equivalent to shutdown -r now)

shutdown -r -now -h time

​ Restart Shut down immediately Shut down time

sync sync data from memory to hard disk

(1) Synchronize data from memory to hard disk sync

(2) Restart sudo reboot

(3) Terminate all activities of the CPU sudo halt

Host Name

View hostname

Modify the host name

sudo hostname new_hostname

Modify the hostnamectl sudo hostnamectl hostname

View system commands
  uname -a
   uname -r

Help command

man Find helper

man man All manuals Press q to exit

man ls find a specific document

--help

2 Commonly used commands

File Directory

ls

ls folder directory View the contents in the file ls /home/zxy View the specified folder directory

Options

-a All files are listed together with hidden files (files with . starting with) (commonly used)

-l List of long data strings, including the properties and permissions of the file, etc.;

Display Description The information listed in each row is:

File type and permissions Number of links File owner File group File size is represented by byte Time of creation or recent modification Name

cd

d Absolute path Switch path

cd relative path switch path

cd ~ or cd back to your home directory

cd - Go back to the last directory

cd .. Return to the previous directory of the current directory

cd -P jump to the actual physical path, not the shortcut path

mkdir

Command to create a folder

mkdir
-m<target attribute> or --mode<target attribute> set the permissions of the directory while establishing the directory;
-p or --parents If the upper directory of the directory to be created has not been established yet, the upper directory will be created together;
--version Displays version information.

sudo mkdir -p 2/3/4

touch

touch Create an empty file

touch #Create a file
 touch {.classpath,README} #Create multiple

-a: or --time=atime or --time=access or --time=use Change only the access time;
-c: or --no-create does not create any files;
-d: <time date> Use the specified date time, not the current time;
-f: This parameter will be ignored and not processed, and is only responsible for solving the compatibility issues of the BSD version touch directive;
-m: or --time=mtime or --time=modify Only change the time of the change;
-r: <Reference File or Directory> Set the date and time of the specified file or directory to the same date and time as the date and time of the reference file or directory;
-t: <datetime> Use the specified date time, not the current time;
--help: online help;
--version: Display version information

cp

cp directory/file that needs to be copied The directory to which the file is copied (../ represents the superior directory) ~ represents the home directory ·

-r Recursively copy the entire folder

cp: Cannot overwrite non-directories with directory '2/' '/home/zhuxiaoyi/1/2'

When you are executingcp -r 2 1Meet during commandcp: Cannot overwrite non-directories with directory '2/' '/home/zhuxiaoyi/1/2'Error, which indicates in the target directory1There is already a name called2non-directory files (probably normal files, linked files, etc.), and you try to overwrite it with a directory,cpThe command does not allow such operations.

Remote file copy: scp

The scp command is used to copy files and directories between Linux. Scp is the abbreviation of secure copy. It is a remote file copy command based on ssh login under Linux system.

scp is encrypted.rcpIt is not encrypted, scp is an enhanced version of rcp.

-1: Use ssh protocol version 1;
-2: Use ssh protocol version 2;
-4: Use ipv4;
-6: Use ipv6;
-B: Run in batch mode;
-C: Use compression;
-F: Specify the ssh configuration file;
-i: identity_file Read the key file used when transferring from the specified file (such as Amazon cloud pem), and this parameter is directly passed to ssh;
-l: Specify broadband limits;
-o: Specify the ssh option to use;
-P: Specify the port number of the remote host;
-p: Keep the last modification time of the file, the last access time and permission mode;
-q: The copy progress is not displayed;
-r: Copy in recursive manner.

Upload
 scp -r /opt/soft/mongodb [email protected]:/opt/soft/scptest

 download
 scp -r [email protected]:/opt/soft/mongodb /opt/soft/
 scp -P 4588 remote@:/usr/local/ /home/administrator

rm

delete

(1) Delete the content in the directory rm xiyou/qujing/

(2) Recursively delete all contents in the directory rm -rf dssz/

Options Function -r Recursively delete all contents in the directory

-f Forces the delete operation without prompting for confirmation.

-v Display the detailed execution process of the instruction

rm -rf *. Delete all files of this type

mv

(1) mv oldNameFile newNameFile (Function description: rename)

(2) mv /temp/movefile /targetFolder (Function description: Move file)

View files

cat

-n Show line number

more

The more directive is a text filter based on the VI editor that displays the contents of text files on pages in a full-screen manner. There are several shortcut keys built in the more command, please refer to the operating instructions for details.

The blank key (space) means to turn a page down;

Enter means to turn "a line" down;

q means leaving more immediately and the contents of the file will no longer be displayed.

Ctrl+F Scroll down one screen

Ctrl+B Return to the previous screen = Output the line number of the current line

f output file name and line number of the current line

lesss

Operation Function Description Blank key Turn down a page;

[pagedown] Flip a line down

[pageup] Flip up a line; /String Search for the function of "String" down;

n: search downward;

N: Search upward; ?String The function of searching upward for the "String";

tail

Output file

-n Number of output lines

-f Real-time update

Output redirection

1 > Coverage

2 >> Additional

Append the content to the README file cat >> README

vim

sudo apt install vim

There are three modes


Vim has many modes, but the three most commonly used are: command mode, insert mode and bottom line mode. The following are the switching methods and operations between them:

General mode (default mode)

When you start Vim, the default entry is command mode. In this mode, you can perform various navigation, copy, paste, delete and other operations, but you cannot enter text directly.

• Move the cursor

  ：

  • h: Move one character to the left.
  • j: Move one line down.
  • k: Move up one line.
  • l: Move one character to the right.
  • gg: Move to the beginning of the file.
  • G: Move to the end of the file.
  • Digital G: Move to the specified line, for example10GMove to line 10.

• copy and paste

  ：

  • yy: Copy the current line.
  • nyy: Copy the current line and the followingn - 1OK, for example3yyCopy the current line and the following 2 lines.
  • p: Paste the copied content after the current cursor position.
  • P: Paste the copied content before the current cursor position.

• delete

  ：

  • dd: Delete the current row.
  • ndd: Delete the current line and the followingn - 1OK, for example3ddDelete the current line and the following 2 lines.

Insert mode

In command mode, press the following key to enter the insert mode, in which you can enter and edit text:

• i: Insert text before the current cursor position.
• a: Insert text after the current cursor position.
• o: Insert a new line on the next line of the current line and enter insert mode.
• O: Insert a new line on the previous line of the current line and enter insert mode.

To return from insert mode to command mode, pressEscJust use the key.

Command Mode

In command mode, press:The key enters the bottom line mode, which is mainly used to execute some file operations, search and replacement commands.

• Save and exit

  ：

  • :w: Save the file.
  • :q: Exit Vim (if the file is not modified).
  • :wq: Save the file and exit Vim.
  • :q!: Do not save the file, force exit Vim.
  • : ! Forced
  • :set nu Show line number
  • :set nonu does not display line number

• Search and replace

  ：

  • /Keywords: Search for the specified keyword in the file and pressnFind the next match and pressNFind the previous match.
  • :%s/original content/new content/g: Replace all "original content" in the file with "new content". For example:%s/hello/world/gPut all the files inhelloReplace withworld。

4. Exit Vim

In command mode, enter the following command to exit Vim:

• :wq: Save the file and exit.
• :q: If the file is not modified, exit directly.
• :q!: Do not save the file, force exit.

data

-d<time string> Displays the time represented by the specified "time string", not the current time

-s<date time> Set the system date time

Display time

(1) date (Function description: display the current time)

(2) date +%Y (Function description: display the current year)

(3) date +%m (Function description: display the current month)

(4) date +%d (Function description: Show what day it is currently)

date +%y%m%d

(5) date "+%Y-%m-%d %H:%M:%S" (Function description: display year, month, day, hour, minute and second)

data -s Set system time

date -s "2017-06-19 20:52:18"

User Group

user

adduser

cat /etc/passwd View user

• -c<Note>: Add the notes text. The notes text will be saved in the comments column of passwd;
  -d<Login Directory>: Specify the start directory when the user logs in;
  -D: Change the preset value;
  -e<valid period>: The validity period of the specified account;
  -f<buffer days>: Specify how many days after the password expires;
  -g<group>: Specify the group to which the user belongs;
  -G<group>: Specify the additional group to which the user belongs;
  -m: Automatically create the user's login directory;
  -M: Do not automatically create the user's login directory;
  -n: Uncreate a group named after the user name;
  -r: Create a system account;
  -s: Specify the shell used by the user after logging in;
  -u: Specify the user ID.

Set the Tom user group
 usermod -g users tom
 Add Tomcat to sys, root group
 usermod -G sys,root tomcat

 usermod -g users tom
 usermod -c "hr tom" tom Add comment

Add new user Create zxy directory in the home directory

adduser zxy

passwd

Set the password to modify

sudo passwd tangseng

id

id zxy

Check whether the username exists

cat /etc/passwd

See how many users have been created

userdel

Delete users

(1) userdel username (Function description: delete the user but save the user home directory)

(2) userdel -r username (Function description: both user and user home directory, deleted)

usermode

Modify user group

sudo usermod -aG sudo zhangzhong #Group is in front User is in back

su

Switch users

su User name (Function description: Switching the user, you can only obtain the user's execution permissions, but you cannot obtain the environment variables)

su - User name (Function description: Switch to the user and obtain the user's environment variables and execution permissions)

Group

groupadd

sudo groupadd xitianqujing

groupdel delete group

sudo groupdel xitianqujing

groupmod -n New group name Old group name Modify group

groupmod -n xitian xitianqujing

usermod -g Group name Username Modify user main group

On Linux and Unix systems, each user has a primary group and possible multiple additional groups. The user's primary group is specified when the user is created, with the default name as the user. When the user creates a new file or directory, these files or directories are assigned to the user's primary group by default.

sudo usermod -g zhuxiaoyi zxy

groups

Find the user's group

groups d

cat /etc/group View user groups

The /etc/group file stores the mapping relationship between the user and the attached group. Each line corresponds to a user group. The third colon is followed by a user list with the group as the attached group. The list is empty to indicate that no user has used it as the attached group.

usermod -aG Group Name Username Specify the user to join the additional group

usermod -aG gdm zxy

deluser

Username Group Name User deleted from the group

deluser zhubajie atguigu

Check how many users there are in a group

grep "^Group name:" /etc/group | awk -F: '{split($4,users,","); print length(users)}'

 ### File permissions

Check who the users in a group are

getent group sudo | cut -d: -f4 | tr ',' '\n'

Permissions

In Linux, the first character means that the file is a directory, a file, or a link file, etc.

• Represents file d Represents directory l Link document (link file)

(2) Positions 1-3 determine that the owner (the owner of the file) has permissions to the file. ---User

(3) In bits 4-6, determine that the group (the owner's same group user) has permissions to the file, ---Group (

(4) Positions 7-9 determine that other users have permissions to the file ---Other

[r] stands for readable (read): can be read, view

 [ w ] means write: it can be modified, but it does not mean that the file can be deleted. The prerequisite for deleting a file is to have write permissions to the directory where the file is located before the file can be deleted.

 [ x ] stands for executable: can be executed by the system

chmod


U: Owner g: All groups o: Others a: All people (sum of u, g, o)

1

chmod +x file name The owner can execute

chmod g+w group can be executed

2

U: Owner g: All groups o: Others a: All people (sum of u, g, o)

r=4 w=2 x=1 rwx=4+2+1=7

Change permissions

chmod ug+w,o-w can set two

chown

Used to change the owner or group authorization of a file or directory, so that the user becomes the owner of the specified file or change the group to which the file belongs. The user can be a user or user D, and the user group can be a group name or group id. A file name can make a file list separated by spaces, and can contain wildcard characters in the file name.

-r Recursive operation

chown [Options] [End User]: [Group] [File or Directory]

chown sunwukong 

When changing the owner, you can also change all groups. First, the owner is the group name.

chown zhangzhong:qianrushi qianrushi
 Change the owner of the qianrushi directory and the group to which it belongs

chgrp

Change the group

chgrp [end user group] [file or directory]

sudo chgrp root 

Pipeline commands

The pipeline command of Linux is '|', through which data can be processed continuously, and its schematic diagram is as follows

Commonly used as receiving data pipeline commands are: less, more, head, tail, while ls, cp, mv cannot.

wc - Statistics of word count
 The number of Bytes, words, or columns of a file can be calculated. If the file name is not specified, or the file name given is "-", the wc instruction will read data from the standard input device.

tar

gzip file (Function description: compress the file, you can only compress the file into *.gz file)

gzip -d -d decompression or gunzip

gunzip file.gz (Function description: Decompress file command)

tar pack

-c generates .tar package file

-v Show details

-f Specify the compressed file name

-z Package and compress at the same time. With gzip attribute

-x Unpacking.tar file

-j has bz2 attribute

tar -zcvf hadoop #Packaging
 tar -zxvf # Decompression
 tar -jxvf.bz2 -C /usr/ #Decompress to the specified path

tar -zxvf file -c decompress path

jar format
 Compression: jar -cvf [target file name].jar [original file name/directory name]
 Unzip: jar -xvf [original file name].jar
 Note: If the Java class library is packaged and the main class exists in the class library, you need to write a META-INF/configuration file, with the following content:
 Manifest-Version: 1.0
 Created-By: 1.6.0_27 (Sun Microsystems Inc.)
 Main-class: the_name_of_the_main_class_should_be_put_here
 Then use the following command to package:
 jar -cvfm [target file name].jar META-INF/ [original file name/directory name]
 In this way, you can use the "java -jar [file name].jar" command to directly run the public static void main method in the main class.

Select commands according to file type:

File Type	Decompression command	Sample command
.	tar -xzf	tar -xzf mysql-8.4.
.gz	gzip -d	gzip -d
.tar	tar -xf	tar -xf

disk

df -h Check disk usage

du View disk space occupied by files and directories

-a Displays large files in the current directory and subdirectories

process

1. Check the user's recent login status
 Last
 lastlog
 2. Check the hard drive usage
 df
 3. Check the file size
 du
 4. Check memory usage
 free
 5. View the file system
 /proc
 6. View the log
 ls /var/log/
 7. View the system error log
 tail /var/log/messages
 8. View the process
 top
 9. End the process
 kill 1234
 kill -9 4333

ps can only view commands in the current window

ps -aux Show all processes

-a Select all processes

-u Show all processes for all users

-x Show process without terminal

ps -ef View the relationship between child and parent processes

UID: User ID  PID:

Process ID  PPID:

Parent process ID

kill kill process

-9 Process number

killall process name

disk

free -m View overall memory

top View system status

top -d n refresh every n seconds

top -i does not display idle or dead processes

operate

Function P is sorted by CPU usage,

This is the default item M is sorted by memory usage

N Sort by PID

q Exit top

After executing the above command, you can sort the queryed process results by P, M, and N.

netstatPort number

netstat -p | grep port number

-n Reject display alias, and can display all numbers that are converted into numbers

-l Only list the service status in listen

-p indicates which process is calling

netstat -nlp | grep 12345   

Check whether the port number is occupied

crontab system timing service

sudo systemctl status crontab 

Check whether the crontab service is started

-e Edit crontab timing tasks

-l Query crontab tasks

-r Delete all crontab tasks of the current user

-u Specify user creation tasks

other

echo

Output content to console

echo [Options] [Output Content]  Options:

 -e: Character conversion that supports backslash control control characters function

\Output\Origin

\n Line break

\t Tab, that is, Tab key

Output redirection

1 > Output Redirection >>Append

l is content

(1) ls -l > File (Function description: Write the content of the list into the file (overwrite))

(2) ls -al >> File (Function Description: The content of the list is appended to the end of the file)

(3) cat file l > file 2 (Function description: Overwrite the content of file 1 to file 2)

(4) echo "Content" >> File

ln

The ln command is used to create links for files. The link types are divided into two types: hard link and symbolic link. The default link type is hard link. If you want to create a symbolic link, you must use the "-s" option.

-sCreate a soft connection

ln -s [original file or directory] [soft link name] After creation is completed, the soft link name is in front of it

ln -s  1111

Delete soft link: rm -rf soft link name, not rm -rf soft link name/

rm -rf 1111

history

View history commands

history n query n command history 10 query last few commands

!n Execute the n command ! In English

!281

!10s Execute the first 10s commands

find

Search range Options

-name Query by file name

find ./ -name "*.txt" Search in the current directory

-user Specify username query

find ./ -user atguigu

-size Query by file size

find ./ -size +200c

b —— Block (512 bytes)

c —— Bytes

w —— Word (2 bytes)

k ——Kilometres bytes

M —— Megabytes

G ——Just byte

whichFind the directory for installation

python@ubuntu:/var/lib/mlocate$ which locate
/usr/bin/locate

grepfilter

The pipe character, "|", means that the processing result of the previous command is output to the subsequent command processing.

compression

wget

Test connection wget --spider URL

download

-c Breakpoint continuous transmission

wget -c /

-O Download Save with different names

wget -O  /?id=1080

-b Background download

wget -b /
tail -f wget-log

Download multiple files

 wget -i
 First, save a download link file:

 cat >
 url1
 url2
 url3
 url4