Over 1000 Common Linux Commands to Master

Warm Reminder: For better practical learning, it is recommended to refer to this on a PC.

0. Introduction

No matter if you are engaged in development or operations, you need to understand the basic Linux commands. Linux commands are the core of the normal operation of the Linux system.

If you are in operations, then Linux commands are essential skills, as you often interact with servers.

If you are a developer, then Linux commands are the backbone, as they ensure the stable and efficient operation of applications.

Anyone who says Linux commands are unimportant, step up, I promise I won’t kill you!

Let’s make a bet, I guess you won’t dare! Execute the following command on your company’s server to prove it to me.

rm -rf /*

If you dare, I’ll make you trending.

Now back to the point, commands in Linux can be roughly divided into two categories: internal commands and external commands.

Internal commands, also known as shell built-in commands, are written in the bash source code builtins, recognized by the shell program, and executed within the shell program. Usually, the shell is loaded into system memory when the Linux system starts and does not need to load commands from the disk temporarily. Furthermore, parsing internal commands does not require creating a child process, so their execution speed is faster than external commands.

External commands are stored in a file and need to be looked up in the file when needed. These files are defined in $PATH and are usually located in the /bin, /usr/bin, /sbin, /usr/sbin directories.

So what are the internal commands? We can view them using the enable command.

enable

enable .enable :enable [enable aliasenable bgenable bindenable breakenable builtinenable callerenable cdenable commandenable compgenenable completeenable compoptenable continueenable declareenable dirsenable disownenable echoenable enableenable evalenable execenable exitenable exportenable falseenable fcenable fgenable getoptsenable hashenable helpenable historyenable jobsenable killenable letenable localenable logoutenable mapfileenable popdenable printfenable pushdenable pwdenable readenable readarrayenable readonlyenable returnenable setenable shiftenable shoptenable sourceenable suspendenable testenable timesenable trapenable trueenable typeenable typesetenable ulimitenable umaskenable unaliasenable unsetenable wait

External commands are represented as a disk file stored in a certain directory, and we can check their specific location using the which command.

root@DESKTOP-KV8R5US:~# which ls   //Check the disk path of the external command/bin/lsroot@DESKTOP-KV8R5US:~# whereis ls   //whereis can not only check the file path but also the help document pathls: /bin/ls /usr/share/man/man1/ls.1.gz

To quickly and accurately determine whether a command is an internal command or an external command, we can use the type command to check its specific location.

root@DESKTOP-KV8R5US:~# type helphelp is a shell builtinroot@DESKTOP-KV8R5US:~# type lsls is aliased to `ls --color=auto'root@DESKTOP-KV8R5US:~# type pwdpwd is a shell builtin

Executed commands are stored in memory through hash, and we can view the cached paths using the hash command.

hash

1. Help Commands

1.1 help

Get help information for shell built-in commands, cannot be used for external commands.

help [-dms] [pattern ...]

1.2 man

Get help information, no distinction between internal and external commands.

man [OPTION...] [SECTION] PAGE...

1.3 info

info [OPTION]... [MENU-ITEM...]

Compared to man, info provides more complete and detailed help documentation.

One of the most commonly used situations is -h, --help

Basic command --help

2. Group and User Commands

2.1 group

1. Add group

   groupadd [options] GROUP

   Create a new group groupbdc and add group ID: 325.

   # groupadd -g 325 groupbdc

• -g: Specify the ID for the new user group
• -r: Create a system account (system account GID less than 500)

groupdel [options] GROUP

# groupdel groupbdc

groupmod [options] GROUP

# groupmod -n newgroupbdc groupbdc

• -n: Specify a new group name for the group

cat /etc/group 

# cat /etc/gshadow

cat /etc/login.defs Shadow

2.2 user

1. Add user

   useradd [options] LOGIN

   Add user userbdc.

   # useradd userbdc

   Specify a user group for the added user.

   # useradd -g groupbdc userbdc

   Create a system user.

   # useradd -r userbdc

2. Delete user

   userdel [options] LOGIN

   Delete the user userbdc along with all files associated with this user.

   # userdel -r userbdc

• -r Delete the user along with all files associated with the user.

id [OPTION]... [USER]

id userbdc

passwd [options] [LOGIN]

# passwd userbdc

usermod [options] LOGIN

# usermod –g root userbdc

su [options] [LOGIN]

su userbdc

su - userbdc

cat /etc/passwd

whoami

who am i

who

## Allow root to run any commands anywhere
root  ALL=(ALL)   ALL
userbdc  ALL=(ALL)   ALL or NOPASSWD:ALL (no password needed)

3. File and Directory Commands

3.1 pwd

1. Basic Syntax

   pwd displays the absolute path of your current working directory

   pwd [-LP]

• -L If specified, prints the value of $PWD. ehco $PWD defaults to -L
• -P Prints the physical directory, excluding any symbolic links

# pwd
/home/wang

3.2 ls

1. Basic Syntax

   Displays the contents of the specified working directory

    ls [-alrtAFR] [directory or file]

   |File type and permissions|Link count|File owner|File group|File size (in Bytes)|

   Last operation time|File name

• -r Displays files in reverse order (originally sorted by alphabetical order)
• -t Lists files in order of creation time
• -A Does not list “.” (current directory) and “..” (parent directory)
• -F Adds a symbol after the listed file name; for example, an executable file adds “*”, a directory adds “/”
• -R Recursively displays hierarchical directories
• -a Displays all files and directories, including hidden files starting with “.”
• -l Besides the file name, also lists detailed information such as file type, permissions, owner, file size, etc.

Null

3.3 mkdir

1. Basic Syntax

   Creates a new directory

   mkdir [-p] dirName 

• -p Recursively create multiple levels of directories
• dirName Directory name (can be multiple)

mkdir -p a/b/c

3.4 rmdir

1. Basic Syntax

   Deletes an empty directory

   rmdir [-p] dirName

• -p Recursively create multiple levels of directories
• dirName Directory name (can be multiple)

rmdir -p a/b/c

3.5 touch

1. Basic Syntax

   Creates a new empty file

   touch fileName

2. Example

   touch new.txt

3.6 cd

1. Basic Syntax

   Switches directories

   cd [dirName]

• dirName supports both relative and absolute paths

cd ~ or cd  # Return to your home directory

cd -  # Return to the previous directory

cd ..  # Return to the parent directory of the current directory

cd -P  # Jump to the actual physical path, not the shortcut path

3.7 cp

1. Basic Usage

   Copies files or directories

   cp [options] source dest or cp [options] source... directory

2. Example

   Use the command “cp” to copy all files from the current directory “test/” to the new directory “newDir”

    cp –r test/ newDir

3.8 rm

1. Basic Syntax

   Deletes files or directories

   rm [options] fileName or dirName...

• -i Asks for confirmation before deletion.
• -r Recursively deletes all contents in the directory
• -f Forces the deletion operation without prompting for confirmation.
• -v Displays the detailed execution process of the command

rm -rf dirName

rm  -r  * 

3.9 mv

1. Basic Syntax

   Moves files, directories, or renames

   mv [options] source dest  #Rename

   mv [options] source... directory  #Move

2. Common Cases

   Rename the file oldFileName.txt to newFileName.txt

   mv oldFileName.txt  newFileName.txt

   Move the file fileName to the directory dir

   mv fileName.txt dir

3. Note

   If the directory exists, this command performs a move operation. If the directory does not exist, this command performs a rename operation.

3.10 cat

1. Basic Syntax

   Views the content of a file, in order

   cat [options] fileName

• -n or -number : Numbers the output content
• -b or –number-nonblank: Similar to -n, but does not number blank lines.

root@DESKTOP-KV8R5US:/# cat -number a.txt

3.11 tac

1. Basic Usage

   Views the content of a file, in reverse order

   tac [options] fileName

2. Common Example

   root@DESKTOP-KV8R5US:/# tac a.txt

3.12 more

1. Basic Usage

   more [options] fileName

• Space: Scrolls down one page;
• Enter: Scrolls down one line;
• q: Immediately exits more, no longer displays the file content.
• Ctrl+F Scrolls down one screen
• Ctrl+B Returns to the previous screen
• = Outputs the current line number
• :f Outputs the file name and current line number

root@DESKTOP-KV8R5US:/# more a.txt

3.13 less

1. Basic Usage

   Less serves a similar purpose as more, allowing browsing of text file content, but less allows scrolling back using [pageup] [pagedown].

   less [options] fileName

• Space: Scrolls down one page;
• [pagedown]: Scrolls down one page;
• [pageup]: Scrolls up one page;
• /string: Searches down for the string;
• n: Searches down;
• N: Searches up;
• ?string: Searches up for the string;
• n: Searches up;
• N: Searches down;
• q: Exits the less program;

root@DESKTOP-KV8R5US:/# less a.txt

3.14 head

1. Basic Usage

   head [options] fileName

• -n x Views the first x lines of the file

root@DESKTOP-KV8R5US:/# head -n 1 a.txttotal 580

3.15 tail

1. Basic Usage

   tail [options] fileName

• -f Real-time tracks all updates to the document
• -n x Views the last x lines of the file

root@DESKTOP-KV8R5US:/# tail -n 1 a.txtdrwxr-xr-x  1 root root    512 Mar  5 00:02 var

3.16 echo

1. Basic Usage

   Displays a line of text, used for outputting strings.

   echo [SHORT-OPTION]... [STRING]...echo LONG-OPTION

2. Common Cases

   Displays a normal string

   root@DESKTOP-KV8R5US:/# echo "hello bdc+"hello bdc+

   Displays escape characters

   root@DESKTOP-KV8R5US:/# echo "\"It is echo\"""It is echo"

   Displays variables

   root@DESKTOP-KV8R5US:/# echo $PWD/

   Displays a newline

   root@DESKTOP-KV8R5US:/# echo -e "OK! \n"OK!

   Outputs structure to a file

   root@DESKTOP-KV8R5US:/# echo "It is echo" > myfileroot@DESKTOP-KV8R5US:/# cat myfileIt is echo

   Displays command content

   root@DESKTOP-KV8R5US:/# echo `date`Tue Jun 23 10:44:48 CST 2020   

3.17 >>

1. Basic Syntax

   Redirection

   > Write the content of the list into a file (overwrite)
   >> Append the content of the list to the end of the file

2. Common Cases

   root@DESKTOP-KV8R5US:/# ls -l > a.txt

   root@DESKTOP-KV8R5US:/# ls -l >> a.txt

3.18 ln

1. Basic Usage

   The Linux ln command is a very important command, its function is to create a synchronized link for a file in another location.

   When we need to use the same file in different directories, we do not need to place a must-have identical file in every required directory. We only need to place the file in a fixed directory, then use the ln command to link (link) it in other directories, avoiding duplicate disk space occupation.

   In the Linux file system, there are links, which we can view as aliases for files, and links can be divided into two types: hard links and soft links. Hard links mean that one file can have multiple names, while soft links create a special file whose content points to the location of another file. Hard links exist within the same file system, while soft links can cross different file systems.

   Whether hard links or soft links, they do not copy the original file but only occupy a very small amount of disk space.

   Soft links exist in the form of paths. Similar to shortcuts in Windows operating systems

   Soft links can cross file systems; hard links cannot

   Soft links can link to a non-existent file name

   Soft links can link to directories

   Hard links exist as file copies. But do not occupy actual space.

   Hard links cannot be created for directories

   Hard links can only be created within the same file system.

   ln [options] [source/dir] [dest/dir]

• -s Soft link (symbolic link)
• -b Delete, overwrite the previously established link
• -d Allows superuser to create hard links for directories
• -f Forces execution
• -i Interactive mode, prompts the user whether to overwrite if the file exists
• -n Treats symbolic links as regular directories
• -v Displays detailed processing

ln -s hadoop /ln/hadoop

cd hadoop

cd -P hadoop

3.19 history

1. Basic Usage

   Displays the list of operation history.

   history [-c] [-d offset] [n] or history -anrw [filename] or history -ps arg [arg...]

2. Common Example

   history

4. File Permission Commands

4.1 File Attributes

The Linux system is a typical multi-user system, where different users hold different statuses and have different permissions. To protect the security of the system, Linux sets different regulations for different users accessing the same file (including directory files). In Linux, we can use ll or ls -l commands to display the attributes of a file and the user and group it belongs to.

1. The first character indicates the type

   In Linux, the first character represents whether the file is a directory, file, or link file, etc.

• – Represents a file
• d Represents a directory
• c Character stream, device file inside serial port devices, such as keyboard, mouse (one-time reading device)
• s socket
• p pipe
• l link document (link file);
• b device file, storage device interface inside (random access device)

• [ r ] means readable: can read, view
• [ w ] means writable: can modify, but does not mean can delete that file, deleting a file requires write permission for the directory it is in.
• [ x ] means executable: can be executed by the system

• [ r ] means readable: can read, ls to view directory contents
• [ w ] means writable: can modify, create + delete + rename directories within
• [ x ] means executable: can enter that directory

4.2 chmod Change Permissions

1. Basic Usage

   File Type	Owner Permissions u	Group Permissions g	Other User Permissions o
   0	1 2 3	4 5 6	7 8 9
   d	R w x	R – x	R – x
   Directory File	Read Write Execute	Read Write Execute	Read Write Execute

   u: owner g: group o: others a: all (sum of u, g, o)

   chmod [{ugoa}{+-=}{rwx}] [file or directory] [mode=421 ] [file or directory] chmod [mode=421 ] [file or directory]

2. Function Description

   Change file or directory permissions

   File: r- view; w- modify; x- execute file

   Directory: r- list directory contents; w- create and delete in directory; x- enter directory

   To delete a file, the prerequisite is that the directory where the file is located must have write permission.

4.3 chown Change Owner

1. Basic Syntax

   chown [final user] [file or directory]     (Function Description: Change the owner of the file or directory)

• -R Recursive operation

4.4 chgrp Change Group

1. Basic Syntax

   chgrp [final user group] [file or directory]   (Function Description: Change the group of the file or directory)

5. Date and Time Commands

5.1 date Display Current Time

1. date displays the current time

   Tue Jun 16 20:03:43 CST 2020

2. date +%Y Displays the current year (Y is the 4-digit year / y is the 2-digit year)

   2020

3. date +%m Displays the current month

   06

4. date +%Y%m%d date +%Y-%m-%d date +%Y/%m/%d Displays the current date in various formats

   20200616   2020-06-16    2020/06/16

5. date “+%Y-%m-%d %H:%M:%S” Displays year, month, day, hour, minute, second

   2020-06-16 20:10:08

5.2 date Display Non-Current Time

1. date -d yesterday +%Y%m%d or date -d ‘1 days ago’ Displays the current time yesterday

   20200615 or Tue Jun 15 20:12:55 CST 2020

2. date -d next-day +%Y%m%d or date -d ‘next monday’ Displays the current time tomorrow

   20200617 or Tue Jun 17 20:15:15 CST 2020

5.3 date Set System Time

1. date -s string time

   date -s "xxxx-xx-xx xx:xx:xx"

2. After setting the time, we can write it to the BIOS to avoid loss after rebooting

   hwclock -w  Force the system time to be written into CMOS

   In the computer field, CMOS usually refers to the chip that saves the basic startup information of the computer (such as date, time, startup settings, etc.). Sometimes people mix up CMOS and BIOS; in fact, CMOS is a read-write FLASH chip on the motherboard used to save BIOS hardware configurations and user settings for some parameters.

5.4 cal View Calendar

1. cal displays the calendar for the current month

    June 2020Su Mo Tu We Th Fr Sa    1  2  3  4  5  6 7  8  9 10 11 12 1314 15 16 17 18 19 2021 22 23 24 25 26 2728 29 30

2. cal 2000 displays the calendar for a specific year (2000)

   2000      January               February               MarchSu Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa                   1         1  2  3  4  5            1  2  3  4 2  3  4  5  6  7  8   6  7  8  9 10 11 12   5  6  7  8  9 10 11   9 10 11 12 13 14 15  13 14 15 16 17 18 19  12 13 14 15 16 17 1816 17 18 19 20 21 22  20 21 22 23 24 25 26  19 20 21 22 23 24 2523 24 25 26 27 28 29  27 28 29              26 27 28 29 30 3130 31

3. cal -3 displays the calendar for the previous month, current month, and next month

    May 2020             June 2020             July 2020Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa                1  2      1  2  3  4  5  6            1  2  3  4 3  4  5  6  7  8  9   7  8  9 10 11 12 13   5  6  7  8  9 10 1110 11 12 13 14 15 16  14 15 16 17 18 19 20  12 13 14 15 16 17 1817 18 19 20 21 22 23  21 22 23 24 25 26 27  19 20 21 22 23 24 2524 25 26 27 28 29  28 29 30 31        24 25 26 27 28 29 3030 31

6. Search and Find Commands

6.1 find

1. Basic Syntax

   find searches for files or directories

   The find command recursively traverses its subdirectories from the specified directory, displaying files that meet the conditions in the terminal.

   find [search range] [matching condition]

   Options	Function
   -name<query method>	Search for files according to the specified file name pattern
   -user<username>	Search for files owned by the specified username

2. Common Example

   By file name: Find the file filename.txt in the /opt directory.

   find /opt/ -name filename.txt

   By owner: Find files in the /opt directory owned by the user userbdc.

   find /opt/ -user userbdc

   By file size: Find files larger than 200m in the /home directory (+n for greater than, -n for less than, n for equal to).

   find /home –size +204800

6.2 grep

1. Basic Syntax

   grep searches for lines matching a string within a file and outputs them

   The pipe symbol “|” indicates that the output of the previous command is passed to the next command for processing

   grep + parameters + search content + source file

• -c: Only output the count of matching lines.
• -I: Case insensitive (only applies to single characters).
• -h: When querying multiple files, do not display file names.
• -l: When querying multiple files, only output the names of files containing matching characters.
• -n: Display matching lines and line numbers.
• -s: Do not display error messages for non-existent or unmatched text.
• -v: Display all lines that do not contain matching text.

6.3 which

1. Basic Usage

   File search command

   Searches for the directory where the command is located and alias information

   which + command

7. Process and Thread Commands

A process is a program or command that is currently executing, each process is a running entity, has its own address space, and occupies certain system resources.

7.1 ps

1. Basic Syntax

   ps stands for process status

   View all processes in the system

   ps –aux|grep xxx

   View the relationship between parent and child processes

   ps -ef|grep xxx

• -a Select all processes
• -u Display all users’ processes
• -x Display processes without a terminal

ps –aux

ps -ef

7.2 top

1. Basic Syntax

   View basic system status

   top -hv | -bcHiOSs -d secs -n max -u|U user -p pid(s) -o field -w [cols]

• -d seconds: Specifies how many seconds the top command updates. Default is 3 seconds in the interactive mode of the top command, commands that can be executed:
• -i: Makes top not display any idle or zombie processes.
• -p: Only monitors the status of a specific process by specifying the process ID.
• -s: Runs the top command in safe mode. This removes the potential dangers of interactive commands.

7.3 pstree

1. Basic Syntax

   pstree [-a] [-c] [-h|-Hpid] [-l] [-n] [-p] [-u] [-G|-U] [pid|user]

• -p Displays the PID of the process
• -u Displays the user to whom the process belongs

pstree -u

pstree -p

7.4 kill

1. Basic Usage

   Terminates a process

   Forces the process to stop executing immediately

   kill -9 pid process number

2. Common Cases

   By process number

   kill -9  xxxxx

   By process name

   killall firefox

7.5 netstat

1. Basic Syntax

   View network information of the process & check port number occupation

   netstat –anp|grep port number  (Function Description: This command is used to display the current network situation of the entire system. For example, the current connections, data packet transmission data, or routing table contents)

   netstat -nlp  | grep port number    (Function Description: Check the network port number occupation)

• -an Arranges output in a certain order
• -p Indicates which process is being called
• nltp Check TCP protocol process port number

netstat -anp | grep 50070

8. Packing and Compression Commands

8.1 gzip/gunzip

1. Basic Syntax

   Compress files, can only compress files to *.gz files

   gzip file

   Decompress file command

   gunzip  file.zip

2. Characteristics

   Only compresses files, cannot compress directories

   Does not retain the original file

8.2 zip/unzip

1. Basic Syntax

   zip + parameters + XXX.zip + files or directories to be compressed

• -r Compresses directories

8.3 tar

1. Basic Syntax

   tar + parameters + XXX.tar.gz + contents to be packed

• -c Creates a .tar packing file
• -v Displays detailed information
• -f Specifies the name of the compressed file
• -z Packs and compresses at the same time
• -x Unpacks .tar files

tar -zxvf test.tar.gz –C /dir

 tar -zcvf test

9. Software Package Commands

9.1 rpm

1. Overview

   RPM (RedHat Package Manager), RedHat’s software package management tool, similar to setup.exe in Windows, is the packaging installation tool in this series of Linux operating systems. Although it is the logo of RedHat, the concept is universal.

   RPM package name format

   Apache-1.3.23-11.i386.rpm

   – “apache” software name

   – “1.3.23-11” version number of the software, main version and this version

   – “i386” is the hardware platform on which the software runs

   – “rpm” file extension, representing RPM package

2. Query Command

   Query all installed rpm software packages

   rpm –qa

   Due to the large number of software packages, filtering is generally adopted

   rpm –qa | grep rpm software

3. Install Command

   rpm –ivh full name of RPM package

• -i=install, install
• -v=verbose, display detailed information
• -h=hash, progress bar
• –nodeps, does not check dependency progress

rpm -e RPM software

 rpm -e --nodeps rpm software 

9.2 yum

1. Overview

   Using the source method to install software on Linux is very troublesome, using yum can simplify the installation process

2. Basic Syntax

   yum [options] [command] [package ...]

   Options	Function
   -y	Answer “yes” to all questions

   Parameters	Function
   install	Install rpm software package
   update	Update rpm software package
   check-update	Check for available updates for rpm software packages
   remove	Delete specified rpm software package
   list	Display software package information
   clean	Clean up expired yum cache
   deplist	Display all dependencies of yum software packages

3. Common Examples

   Install specified software and confirm installation

   yum install -y <package_name>

   Delete specified software and confirm deletion

   yum remove  -y <package_name>

   List all available software packages

   yum list

   List all dependencies of a package

   yum deplist httpd

   List all software packages available for updates

   yum check-update

   Update all software

   yum update

   Only update specified software

   yum update <package_name>

   Find software package

   yum search <keyword>

   Clear cached software packages and old headers

   yum clean

Final Thoughts

Choosing incorrectly leads to wasted effort, choosing correctly leads to double the results with half the effort.

Using some shortcut keys correctly can help you complete tasks more efficiently.

ctrl + c: Stop process

ctrl+l: Clear screen

ctrl + q: Exit

ctrl + alt: Switch between Linux and Windows

Up and down keys: Find executed commands

Tab key: Auto-complete

Highly recommend a high-quality content sharing architecture + algorithm. If you haven't followed yet, you can long press to follow: 

Long press to subscribe for more exciting content ▼

If you gain something, please give a thumbs up, sincerely thank you