30 Essential Linux Basic Commands You Must Know

Linux is basically an open source operating system (OS), which has been favored by people who have sound technical background along with for people who are just sick of seeing the lack of liberty and right kind of privacy in Windows and other operating systems. And when it comes to using the Linux, you need number of commands, which has to be employed for the primary functions including setting up the date, time, changing the password and even when you want to log out from the Linux based PC. 

Though the professionals using the Linux based systems are well versed with these steps or commands, however, the beginners are simply not aware of the same. They often are seen encountering bad time while working on the Linux based systems. The novices are supposed to press the key- Enter to start putting down the respective commands to see the needful. And if you are seen struck at any point of time, you have to press the command for help as well. So using this interface is pretty different from the user friendly interface of Windows, but it has other benefits over the other operating systems. The following are the top ten commands for novices, let’s check them out:

Important note: Linux commands are case sensitive.

Commands For Beginners

clear

This is the command to clear screen. When you work with Linux you have a great amount of possibility of trying loads of commands. This means you need to clean up the screen time and again so that you could focus on your desired job. In order to clear the mess you need the command of clear wherein you simply have to type ‘clear’ over the command prompt to see things clean over your screen. This command is also useful when you have to type long commands, which can confuse the users to see different details over the screen.

ls 

Shows list of files and directories.
This is probably one of the most commonly typed commands. This has many options to see different types of files and it also supports wild cards.

• Show all files in current directory
ls
• Show all files in a directory /mydir/some/path
  
  ls /mydir/some/path
  
• Display details of all file in the list 
  ls -l
• Display all hidden files as well (including the files name start with a do )
  ls -a
• Display all file that have names starting with my
  
  ls my*

cd 

Used to change directory

• Go to the home directory of logged in user
  cd
• Go to a specific directory named /mydir/some/path
  cd /mydire/some/path

cp

Copy a file or directory from one location to another. 

• Copy a file name file1 with name file2
  cp file1 file2
• Copy the directory name dir1 to dir2
  cp -r dir1 dir2

mkdir

Create one or more directories

• Create a directory named mydirecory
  mkdir mydirectory
• Create 3 directories name dir1, dir2 and dir3
  mkdir dir1 dir2 dir3

man
Used to read more details about how to use any command
There are hundreds of commands and each of these commands are supported with dozens of options. You can always use this command to explore more options supported by a command. 

• Show help for ls command 
  man ls
• Show help for grep command 
  man grep

mv - Rename command

Used for renaming a file or directory. 

Rename file1 to file2

mv file1 file2

System Information

date

The command to see current date or set system date/time
In order to type the date in two digit month formats, two digit time formats, two digit date, two digit minutes, you need this command. This will in changing and setting the date and time over your Linux based computer. This command is very much useful when you want to log on being a root.

• Display current date
  date
• Set current system date to "June 20, 1985, 5:27 PM"
  
  date 0620172785

df

The command for checking available disc space
The computer users are often known to check the availability and consumed memory space over their systems for both the Linux and Windows desktop PCs. You can easily check the amount of memory available over the disk at your Linux system by simply typing the command of DF. It helps in offering you the status of file system disk space over your Linux based system.

df -h

du

Display disk space use by each file in the file system 

• Display disk usage by each file in Documents directory
  du -h Documents
• Display disk usage by the whole Documents direcotry 
  du – sh Documents

top

Display the top running processes on the system with memory and cpu utilization. 

• Display all top running processes
  top
• Display all top running processes from user fromdev 
  top -U fromdev

ps

Show the status of running processes

• Display all running process status for current user
  ps
• Display the list of all running processes on system with their status.
  ps -al

uname 

Find information about version and details of operating system
uname -a

File Operations

gzip

This command will compress a file in gzip format. 

gzip file1

gunzip

Uncompress the gzip file.
gunzip file1.gz

tail

Display last few lines contents of a file. Very useful to watch latest content updates on log file.

• Watch running content of a logfile name logfile1 
  tail -f logfile1
• Display last 100 lines of a file name myfile
  tail -100 myfile

scp

Copy a file to or from a remote host

Copy the file "myfile.txt" from a remote host to the local host
scp your_username@remote-server:foobar.txt /path/to/local/directory

Copy a local file myfile.txt to remote server 
scp myfile.txt your_username@remote-server:/path/to/copy/

Copy the directory "mydir" from the local host to a remote host's directory "myremotedir"

scp -r mydir your_username@remote-server:/path/to/remote/directory/myremotedir

sftp

This can be used for doing file transfer using secure ftp protocol. To open a sftp command prompt on a sftp server try this

sftp your_username@remote-server

cat

Used to display the content of the file on console without opening it in a editor.. 
cat myfile

more 

Used to display the content of a file on console with option to navigate in case the content is too large to fit in screen.
more myfile

find

Find a file or directory on the system using this command

• Find a file myfile.txt in current directory and its subdirectories. 
  find . -name “myfile.txt”
• Find all files in Documents directory that are larger that 25MB in size
  find . -size +25M -exec du -h {} \;
• Find all .doc files on the system that have been modified in the last 5 days.
  find . –name “*.doc” –mtime -5
• Find all .txt files on the system that were modified in last 15 minutes
  find . –name “*.txt” –mmin -15
• Find all files that contain a string “I am inside file”.
  find . -name "*" -exec grep -i -H "I am inside file" {} \;

grep

This command is used to search all the lines in all files in a specified location containing a string. 

• Search for a specific string “myname” in a file myfile.txt
  grep “myname” myfile.txt
• Search for a specific string “myname” with ignoring the case in a file myfile.txt
  grep -i “myname” myfile.txt
• Search for a specific string “myname” in a all files in current directory
  grep “myname” *
• Search for full word “myword” in a file myfile.txt
  grep -w “myword” myfile.txt
• Search a string “myname” in all files in all subdirectories recursively 
  grep -r “myname” *

rm 

Remove a file or directory using this command

Remove a file name myfile.txt 
rm myfile.txt

Remove a directory mydir 
rm -r mydir

Remove a file myfile.txt forcefully
rm -f myfile.txt

chmod

The command for manipulating the file permissions
For better security, the permissions for file in Linux OS are categorized into different groups, users and other sections. You have the option of controlling the permissions by assigning the users under the given divisions via the command of ‘chmod’. These permissions would help the users to write, read and execute the respective files. This option is very much handy when you have to run a script in order to install the package, which remains non executable in the default for security reasons. With the command of ‘chmod +x’ you could end up making the script executable over your Linux system.

• Provide execute permission on a file myfile.txt to all users
  chmod +x myfile.txt
• Provide read permission on a file myfile.txt to all users
  chmod +r myfile.txt
• Provide full permissions (read/write/execute) on a file myfile.txt to yourself but everyone else has only read and execute
  chmod 755 myfile.txt
• Provide full permissions (read/write/execute) on a file myfile.txt to everyone
  chmod 777 myfile.txt

chown 

Change ownership of a file. You should be either root or the owner of the file to successfully run this command. 

Change the ownership of a file myfile.txt to another_user who is part of another_group

chown another_user:another_group myfile.txt

Change the ownership of a directory mydir1 recursively to another_user who is part of another_group

chown -R another_user:another_group mydir1

Other Useful Commands

passwd 

This is the command for changing the password. Passwords play an important role in securing your data found in your desktop computer. In order to keep the system full proof against the hacking attacks, you need to keep on changing your passwords every three months. The users over Linux computers could do the same using a particular command of ‘change password’ over the command prompt and do the needful. After you type the command, all you need to do is to type the new password twice, and you are done with the same.

logout

Command for logging out. By typing this command, you would be logged out from your Linux based computer. This command will help in disconnecting from your Linux based PCs or simply help in logging out the session that you are seen over your desktop. All you need to do is to remember the account you have logged out as it may bring a couple of security issues. Hence it is highly suggested to use a log out the moment you finish your task over your PC.

kill -9

The command to terminate the process by its process id. You may find certain Linux applications not responding at such junctures, you could simply get away from this scenario by typing the kill command, which will help in terminating the process. For this you need the process ‘PID’ of the particular application, which could be done with the help of “ps” command. You could further use this command to kill the command to terminate the application, which is not responding.

Terminate a process with with ID 1234

kill -9 1234

”>” - The operator to redirect output

Though this may not be called as a command by many yet it is among the important steps to master while you start working with Linux over the command line. For this you need several tools, which also include the pipe. These help in redirecting the output (that is often printed over the screen) somewhere else like the text file or any other application. This command is used to complete any file over the Linux system.

• Copy content of file1 to file2
  cat file1 > file2
• Append content of file1 to file2
  cat file1>>file2
• Create a new file myfile.txt with text “some text” 
  echo “some text” > myfile.txt

pipe (|) operator

The pipe operator is a powerful operator that can be used to join two commands together. Usign this operator output of one command can become input to another command. For example

• Display live occurrence of text “myname” in a file myfile.log
  
  tail -f myfile.logs | grep “myname”
• Count the number of lines in a file myfile1 
  cat myfile1 | wc -l
• Find all running java processes on a system
  ps -aef | grep “java”
• Find all .txt files containing text “myname” 
  find . -name “*.txt” | xargs grep “myname”

history

This is the command for recall. 
You need to use history to rerun any command. If you enter this command without any kind of switch, you end up getting the history list along with the line numbers. Also, you could even perform some additional search of the given history list with this command.

exit

Use this to quit the command line shell on a linux system.

Final Word

Commands have great importance in Linux. You cannot move an inch while using the Linux based PC. The above are some of the best commands for the beginners, which are mandatory to run a Linux based computer.

It can be really frustrating to get started on any linux system if you do not have idea about basic operations. I hope these commands empower you to do something more productively. 

Are you still facing issues in doing something on linux? Share your experience on comments? 

Posted in: LUNIX