linux-commands.md

Linux

Linux is an open-source operating system based on the Unix architecture, widely used for its stability, security, and flexibility. It powers servers, desktops, and embedded systems, offering A wide range of distributions like Ubuntu, Fedora, and CentOS.

Command Line Interface

CGI (Common Gateway Interface) is A protocol used to enable interaction between web servers and external programs, allowing dynamic content generation on websites.

Graphical User Interface

GUI (Graphical User Interface) is A visual interface that allows users to interact with Ad system or software through graphical elements like windows, icons, and buttons, instead of using text-based commands.

Windows uses GUI where Linux uses both CLI & GUI.

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Linux Commands

• pwd : Gives Information of on what directory you are right now. (Parent)

• ls : Gives what your current pwd directory contains. (Children)

• mv : Move Command
  Example : mv txt1 folder/

  This command Move txt1 inside folder file

• cp : Copy Command
  Example : cp txt2 folder/

  This command Copy txt2 inside folder file

• cd : Used when we need to enter inside some other directory. Example : cd <directory>

  Through this command we can enter inside desired directory. You can use ls Command afterward to Go inside <directory> directory.
  You can use cd .. Command afterward to goto home directory.

• mkdir : used to make directory.
  Example : mkdir fl

  through this command you can make directory inside or outside your directory.

Types of Users :

1. Root User : Controls Terminal as Admin.
2. Regular User : A regular user with limited access.

To use terminal as Admin use command sudo su .

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Linux 50 Commands

• ls : list the files and directories in the current directory
  ls

• cd : change the current directory
  cd <dir_name>

• mkdir : create a new directory
  mkdir Vasu

• rmdir : remove a directory
  rmdir Vasu

• pwd : print the current working directory
  pwd

• cp : copy files or directories

We will copy a file called example.txt from the current directory to a directory called backup
cp example.txt backup/

• mv : move or rename files or directories
  mv example.txt backup/

• rm : remove files or directories
  rm example.txt

• touch : create a new empty file or update the timestamp of an existing file
  touch shayan.txt

• cat : concatenate and display files
  cat example.txt

• man : manual for a command
  man ls

• htop : an interactive process viewer and system monitor
  htop

• chmod : change the permissions of a file or directory

// The first digit represents the owner of the file/directory
// The second digit represents the group that the file/directory belongs to
// The third digit represents all other users
// 0 (no permission)
// 1 (execute only)
// 2 (write only)
// 3 (write and execute)
// 4 (read only)
// 5 (read and execute)
// 6 (read and write)
// 7 (read, write, and execute)

chmod 700 file.txt

• chown : change the owner of a file or directory
  chown new_owner example.txt

• tar : create or extract compressed archive files

// x: extract files from an archive
// t: list the contents of an archive
// r: append files to an existing archive
// z: use gzip compression
// j: use bzip2 compression
// cf: create file
// xf: extract file
tar cf archive.tar file1 file2 file3

• gzip : compress files
  gzip file.txt

• gunzip : decompress compressed files
  gunzip file.txt.gz

• ssh : connect to a remote server securely
  ssh username@server_address

• scp : securely copy files between systems
  scp myfile.txt user@remotehost:/home/user/

• ping : test network connectivity
  ping 8.8.8.8

• ifconfig : display or configure network interfaces
  ifconfig

• netstat : display network connection information
  netstat

• route : view or configure network routing tables
  route [options] [add/delete/show]

• top : display system resource usage and processes
  top

• ps : display information about running processes
  ps aux

• kill : terminate a process
  kill [PID]

• systemctl : control system services and settings

// Start the nginx service
systemctl start nginx

// Check the status of the nginx service
systemctl status nginx

// Stop the nginx service
systemctl stop nginx

• service : control system services
  service apache2 start

• useradd : add a new user to the system
  useradd Harry

• passwd : change the password for a user
  passwd Harry

• userdel : delete a user from the system
  userdel Harry

• su : switch user to become another user
  su John 

• sudo : execute a command as another user or with elevated privileges
  sudo

• uptime : display system uptime and load average
  uptime

• df : display disk space usage
  df

• du : display disk usage by file or directory
  du

• mount : mount a file system
  sudo mount /dev/sdb1 /mnt/USB

• umount : unmount a file system
  sudo umount /mnt/USB

• date : display or set the system date and time
  date

• whoami : display the current user name
  whoami

• which : locate a program or command in the system path
  ls

• finger : displays all the information about user
  finger Harry

• uname : display system information
  uname
uname -a

• history : display a list of previously executed commands
  history

• echo : display text or variables to the console
  echo 'I need Tshirt from codeswear!'

• tee : redirect output to both a file and the console
  $ ls | tee file.txt

• locate : locate any file on the system
  locate file.txt

• sort : sort lines of text in a file or input
  cat file.txt
banana
orange
apple
sort file.txt
apple
banana
orange

• uniq : remove duplicate lines from a file or input
  cat file.txt
apple
orange
banana
apple
banana
uniq file.txt
apple
orange
banana

• head/tail : display the first/last few lines of a file or input
  #display first 10 lines
head file.txt

display last 10 lines
tail file.txt`