DevOps

What is Linux?

Linux is an open source operating system. Just like other operating system (Windows, Mac OS and Android etc.). An operating system is software that manages all of the hardware resourcess associated with your desktop or laptop.

what is Shell?

A shell is user interface or an environment for accessing operating system services. Using shell we can run our command, program and shell script.

Type of shell

• There are two type of shell. ### 1. Command line shell
  • Command line shell require the user to enter text command to excecute specific program. For Example
    • Bash (the default shell for Linux and macOS)
    • DOS
    • cmd.exe (the default shell for Windows)

      2. Graphical shell (GUI)

  • Graphical shells provide a GUI for interacting with the operating system. For Example
    • macOS Finder
    • Windows Explorer
    • GNOME Shell (the default shell for GNOME desktop environment)
    • KDE Plasma (the default shell for KDE Plasma desktop environment)

Linux Commands

1. whereis - Find the path of an executable file.

2. man <command_name> - Get information about a command.

3. List command:
   • ls - Show all the files and folders under a specific folder/directory.
   • ls -a - Show all the file/folder including hidden files.
   • ls -al - Show all the file/folder including hidden files with detailed information.
   • ls -R - Show all the file/folder in a directory and its subdirectory recursively.
4. pwd (Print Working Directory)
   • pwd - It’s print current working directory
5. cd (Change Directory):
   • cd <folder_name> - Go to a specific folder/directory.
   • cd . - Go to the present directory.
   • cd .. - Go to the previous directory.
6. cat (Concatenate or Display Files):
   • cat <file_name> - Read/display the data of a file.
   • cat > <file_name> - Create a new file.
   • cat <file1> <file2> > <file3> - Concatenate multiple files together.
   • cat <file1> | tr a-z A-Z > <file2> - Translate file1 data to uppercase and insert into file2.
7. man (Manual):
   • man <command_name> - Get information about a command.
8. mkdir (Make Directory)
   • mkdir <folder_name> - use to create new folder/directory
9. touch (Create New File)
   • touch <file_name> - user to create empty new file
10. cp (Copy Command) -
    • cp <file_name> <destination> - use to Copy a file.
    • scp command
      • scp <file_name> username@destination_host:/home/folder_addr> - it’s used to copy local to remote server
      • scp username@destination_host>:/home/folder/file_name /home/folder/file1 - it’s used to copy remote to lcoal

11. man (use to give info about any command)

    • man <command_name> - it’s give the info about commands

12. tr (use to translate or delete the character)

    • cat <file1> | tr a-z A-Z > <file2> - it’s traslate file1 data to upper case and insert into file2

13. mv ( move or rename file/directory)

    • mv <source_file> <destination_file> - its move to destination file

    • mv <source_file> <new_file> - its rename the files

14. rm (remove file)
    • rm file_name - remove files
      • -r - Recursively delete directories and their contents.
      • -f - Forcefully delete files without asking.
      • -i - Prompt before deleting each file.
      • -l - Prompt only once before deleting multiple files.
      • -v - Verbosely list the files that are being deleted.
15. df (disk free)
    • df - used to check the capacity and storage details.
      • -m - in megabytes
      • -h - in gigabytes
16. du (disk usage)
    • du - show the disk usage
      • -h - human readable
17. head
    • head <file_name> - display first 10 lines.
18. tail
    • tail <file_name> - display last 10 lines.
19. diff
    • diff <file1> <file2> - show the different between two files
20. locate
    • locate <file> - to find out file.
21. find
    • find <file/folder_name> - Find a file/folder.
    • find <dir_name - find files inside directory.
    • find .-type d - Show only directory.
      • .-type f - show only files.
      • .-type f -name "*.txt" - Show only files with that specific name.
      • .-type f -iname "*.txt" - Show only files with that specific name - not case sensitive
      • .-type f -mmin -20 - Show files which modify less than 20 min ago.
      • .-type f -mmin +20 - show files which modify more than 20 min ago.
      • .-type f -maxdepth 2 - Will only show 1 folder deep.
      • .-size +1k - will only show file/folder with size of 1kb
22. chmod (change file mode access)
    • chmod 777 <file_name> - will change file permission access
23. chown (change owner of file/dir)
    • chown <owner_name> <file_name> - change file owner i.e - chown root file1.txt - file1.txt only access by root user
24. grep (search the text in the file)
    • grep <text> <file_name> - search text in files
      • -w <text> <file_name> - search and show whole text
      • -n <text> <file_name> - show line number of text
      • -i <text> <file_name> - show text without case sensetive
      • -c <text> <file_name> - print the number of match found
      • -v <text> <file_name> - invert the search, so that only show the text that are not with search
    • grep -win <text> ./*.txt - search text in all .txt file that is available in current directory

Terminal Shortcut:

• ctrl+a - cursor go to at start point
• ctrl+e - cursor go to at end point
• ctrl+k - remove all the word after the cursor
• ctrl+u - remove all the word
• history - To see all the previous used commands

Networking commands

• nslookup - To get the IP address of Domain name. i.e - nslookup google.com

• netstat - To check the network status.
• hostname - To check the hostname.
• whoami - To check the current user.
• ping google.com - To check the connectivity

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