Linux is an open-source operating system based on the Linux kernel. This operating system was designed for PC but later evolved to use in a wide range of devices and applications. You will be surprised to know that Android is also powered by Linux. Linux has a powerful command line utility but you need to learn Linux commands to use it properly. So, I have made a list of Linux commands. Have a look at the Linux commands cheat sheet.
Basic Linux commands
| Command | Description |
| ls | Lists all files and directories in the present working directory |
| ls -R | Lists files in sub-directories as well |
| ls -a | Lists hidden files as well |
| ls -al | Lists files and directories with detailed information like permissions, size, owner, etc. |
| cd or cd ~ | Navigate to the HOME directory |
| cd .. | Move one level up |
| cd | To change to a particular directory |
| cd / | Move to the root directory |
| cat > filename | Creates a new file |
| cat filename | Displays the file content |
| cat file1 file2 > file3 | Joins two files (file1, file2) and stores the output in a new file (file3) |
| mv file “new file path” | Moves the files to the new location |
| mv filename new_file_name | Renames the file to a new filename |
| sudo | Allows regular users to run programs with the security privileges of the superuser or root |
| rm filename | Deletes a file |
| man | Gives help information on a command |
| history | Gives a list of all past commands typed in the current terminal session |
| clear | Clears the terminal |
| mkdir directoryname | Creates a new directory in the present working directory or an at the specified path |
| rmdir | Deletes a directory |
| mv | Renames a directory |
| pr -x | Divides the file into x columns |
| pr -h | Assigns a header to the file |
| pr -n | Denotes the file with Line Numbers |
| lp -nc , lpr c | Prints “c” copies of the File |
| lp-d lp-P | Specifies the name of the printer |
| apt-get | Command used to install and update packages |
| mail -s ‘subject’ -c ‘cc-address’ -b ‘bcc-address’ ‘to-address’ | Command to send email |
| mail -s “Subject” to-address < Filename | Command to send an email with an attachment |
File Permission commands
| Command | Description |
| ls -l | to show file type and access permission |
| r | read permission |
| w | write permission |
| x | execute permission |
| -= | no permission |
| Chown user | For changing the ownership of a file/directory |
| Chown user:group filename | change the user as well as a group for a file or directory |
Environment Variables command
| Command | Description |
| echo $VARIABLE | To display the value of a variable |
| env | Displays all environment variables |
| VARIABLE_NAME= variable_value | Create a new variable |
| Unset | Remove a variable |
| export Variable=value | To set the value of an environment variable |
User management commands of Linux
| Command | Description |
| sudo adduser username | To add a new user |
| sudo passwd -l ‘username’ | To change the password of a user |
| sudo userdel -r ‘username’ | To remove a newly created user |
| sudo usermod -a -G GROUPNAME USERNAME | To add a user to a group |
| sudo deluser USER GROUPNAME | To remove a user from a group |
| finger | Shows information of all the users logged in |
| finger username | Gives information about a particular user |
Networking command
| Command | Description |
| SSH username@ip-address or hostname | login into a remote Linux machine using SSH |
| Ping hostname=”” or =”” | To ping and Analyze network and host connections |
| dir | Display files in the current directory of a remote computer |
| cd “dirname” | change the directory to “dirname” on a remote computer |
| put file | upload ‘file’ from local to a remote computer |
| get file | Download the ‘file’ from the remote to the local computer |
| quit | Logout |
Process command
| Command | Description |
| bg | To send a process to the background |
| fg | To run a stopped process in the foreground |
| top | Details on all Active Processes |
| ps | Give the status of processes running for a user |
| ps PID | Gives the status of a particular process |
| pidof | Gives the Process ID (PID) of a process |
| kill PID | Kills a process |
| nice | Starts a process with a given priority |
| renice | Changes priority of an already running process |
| df | Gives free hard disk space on your system |
| free | Gives free RAM on your system |
VI Editing Commands
| Command | Description |
| i | Insert at cursor (goes into insert mode) |
| a | Write after the cursor (goes into insert mode) |
| A | Write at the end of the line (goes into insert mode) |
| ESC | Terminate insert mode |
| u | Undo last change |
| U | Undo all changes to the entire line |
| o | Open a new line (goes into insert mode) |
| dd | Delete line |
| 3dd | Delete 3 lines |
| D | Delete the contents of the line after the cursor |
| C | Delete the contents of a line after the cursor and insert new text. Press the ESC key to end insertion. |
| dw | Delete word |
| 4dw | Delete 4 words |
| cw | Change word |
| x | Delete the character at the cursor |
| r | Replace character |
| R | Overwrite characters from cursor onward |
| s | Substitute one character under the cursor and continue to insert |
| S | Substitute the entire line and begin to insert at the beginning of the line |
| ~ | Change case of individual character |
