Basic Linux Commands


title: Basic Linux Commands

Basic Linux Commands

When starting out with Linux, there are some basic commands everyone should know.

  1. cd – change directory
  • cd followed by a directory or file path will take you inside that directory (folder).
  1. ls – list command
  • Type ls and the contents of the current directory will be displayed.
  • Two common flags used with ls are -l and -a, they can be used together and chained as such: ls -la. The -l flag will show you files in list order and in long format including a display of permissions, -a will show dot type files which are typically hidden in a GUI file finder such as .env files
  • Flag ordering does not matter, so the previous command could be written as ls -al
  1. man – manual command
  • Shows you the manual for the following command. This is very helpful when trying to figure out how an unfamiliar command works. For example, type man ls for everything you need to know about the ls command. Type q to exit.
  • You can search a term or phrase on entire manual pages database to discover which pages match on them using the parameter -k. For example, man -k "open files" search the term “open files” on the synopsis of all man pages.
  1. pwd – path
  • Type pwd to display the path to your current directory.
  1. mkdir – make directory
  • This command, followed by the name you wish to name your directory, creates a new directory. mkdir folder1 will make a new directory called folder1.
  1. rmdir – remove directory
  • Removes the directory that follows the command. rmdir folder1 will delete the directory named folder1 if it exists.
  1. rm – remove
  • This command removes files, not directories. rm file.txt will remove the file named file.txt as long as it exists and is in the current directory.
  • To remove directories that have files inside use rm -r DIRECTORY_NAME. r mean recursive and will delete both directory and files inside.
  • Warning, this command is capable of destroying entire systems, use with caution
  1. touch – sets modification and access times of files, creates new files
  • The touch command sets the modification and access times of files to the current time by default. To set the access time and/or modification time of files to a different date or that of another file, certain flags can be used with the command. If the touch command is used with a filename that does not exist, it creates the file. touch new.txt will create a new text file with the name new.
  1. mv – move
  • Use the mv command to move files through the command line. We can also use the mv command to rename a file. For example, if we want to rename the file “text” to “new”, we can use mv text new.
  • Warning, this command is capable of destroying entire systems, use with caution
  1. right-click – copy and paste
  • This one is less of a command and more of a how-to, however, it is very useful for doing almost anything in a terminal on Linux. To begin, highlight text like normal and then “right-click” on your mouse to copy a selection. You should see the highlighted portion become un-highlighted, this means you copied the selection. Now “right-click” on where you want to paste the selection and you’re done.
  1. less – view file content
  • Use less filename.txt to view contents of a file and navigate through them. By default, less will go through the file page by page.
  1. cat – display file’s textual contents
  • Use this command to display text from within a given file on your terminal. Entering cat myFile.txt in your terminal will display the contents of the file myFile.txt on screen. The cat command can be a very handy tool when used with the terminal pipes.
  1. clear – clear terminal
  • Use clear to simply clear all output from your terminal.
  1. cp – copy files and directories
  • Use ‘cp’ to copy a file or a direcotry with files inside it to another location using command cp CURRENT_FILE-LOCATION DESTINATION_FOLDER. Add ‘-r’ flag to copy a directory that is not empty.
  1. du – estimate file space usage
  • Use ‘du’ to estimate file space usage. du is abbreviation of “disk usage”. This command tool reports usage by given directory
  1. df -h Checks disk space in human readable form
  2. ln – link LINKNAME to TARGET file/directory
  • Link is pointer which connects file name to actual bytes of data on the disk. More than one link can point on the same data.
  • Use ln to create a link to targeted file with linkname. Link to target is created in current working directory. By default ln creates hard link and requires existance of TARGET file/directory. If we add -s(–symbolic) to the command, symbolic link will be created.
  1. top – shows the system load
  • Use top to get information about running processes of your system, the amount or RAM they allocate and the CPU percentage that they use. ‘Top’ is interactive so do not forget to press q when you want to quit.
  • Shows the size, amount used, amount available and capacity percentage of mounted drives/partitions.
  1. grep – The grep searches any given input files, selecting lines that match one or more patterns.
  • use grep to find a file, a directory, some text in the file/directory.
  1. sudo – execute a command as super user
  • A widely used command in the Linux command line, sudo stands for “SuperUser Do”. So, if you want any command to be done with administrative or root privileges, you can use the sudo command.
  1. kill – stops runing process
  • The kill command sends a signal to a running process. This default action normally stops processes. If you want to stop a process, specify the process ID (PID) in the ProcessID variable. The shell reports the PID of each process that is running in the background (unless you start more than one process in a pipeline, in which case the shell reports the number of the last process). You can also use the ps command to find the process ID number of commands.
  1. find – search for files in a directory hierarchy
  • find searches the directory tree rooted at each given file name by evaluating the given expression from left to right, according to the rules of precedence, until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name.
  1. ps – Show active processes
  • Use ps to see running processes, and their process IDs
    Example: ps
  1. history
  • Use history to see previously entered commands
    Example: history
  1. passwd – changes user passwords
  • Use passwd -h to look at the options available for changing passwords.
  1. whoami – display current user
  • Use this command to display the username of the current user to the console.
  1. chmod – change permission
  • Use ‘chmod’ to make a file executable and to change the permissions granted to it in Linux. For the example , imagine you have a file named myFile.txt . But it can’t executable because you not have a permission to this file , you can use the command chmod +x myFile.txt or chmod 755 myFile.txt.
  1. locate
  • Used to locate a file in the system
    Example:
locate sample.txt /home/rajasimha/Desktop/sample.txt

Useful Resources for Practice:

  • JSLinux: Run the terminal inside your browser. Great for practice.
  • LearnShell: Interactive Linux shell (terminal) tutorials.
  • LinuxJourney: A collection of beginner-friendly terminal tutorials.

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