HB Computer Security | Aide Memoire
  • Introduction
  • Core Technical Skills
    • Core Skills
      • Linux
        • Getting to Know Linux
          • Using the Shell
            • Shells, Terminals, and Virtual Consoles
            • Choose your Shell
            • Shell Commands
              • Non-PATH Commands
              • Command History
                • Command Line Editing
                  • Keystrokes for Navigating Command Lines
                  • Keystrokes for Editing Command Lines
                  • Keystrokes for Cutting and Pasting Text from within Command Lines
                • Command Line Recall
                  • Keystrokes for Command Line Recall
              • Connecting and Expanding Commands
                • Piping Between Commands
                • Sequential Commands
                • Expanding Commands
            • Shell Variables
              • Common Shell Variables
            • Aliases
            • Create your Own Shell Environment
              • Modification Ideas
          • Navigating the Linux File System (LFS)
            • Filesystem Commands
            • Listing Files and Directories
            • File Permissions and Ownership
              • Modifying Permissions with chmod
              • Modifying Default Permissions with umask
              • Change File Ownership with chown
            • Copying, Moving, and Removing Files
            • Finding Files
              • locate
              • find
              • grep
            • Downloading Files
              • axel
              • wget
              • curl
                • User-Agent: Googlebot
          • Working with Text Files
            • Using vim and vi to Edit Text Files
              • Starting with vi
              • Adding Text
              • Moving Around in the Text
            • Text Manipulation
        • System Administration
          • Installing Linux
            • Installing from Live Media
            • Installing in the Enterprise
            • Partitioning Hard Disks
              • Tips for Creating Partitions
          • Account Administration
            • The root Account
              • Becoming root with su
              • sudo
                • The /etc/sudoers File
                • Granting sudo privileges
                  • visudo Guidance
                • Useful sudo Hints
            • Other Administrative Accounts
            • Standard User Accounts
              • Risks of userdel: Orphaned Files
          • Graphical Remote Administration
            • Cockpit
              • Installation Guide
            • Remote Desktop Protocol with xrdp
              • Installation and Configuration
            • Remote Desktop with vnc
              • Installation and Configuration
              • Running VNC as a System Service
          • Managing Running Processes
            • Listing Processes
              • ps
              • top
              • htop
            • Backgrounding and Foregrounding
              • Starting a Background Process
              • Using Foreground and Background Commands
            • Killing and Recining Processes
              • kill and killall
          • Managing Software
            • Managing Software from the Desktop
            • Going Beyond the Limitations of Software Center
              • Debian Packages
                • Advanced Package Tool (apt)
                • Repositories
                • dpkg
        • Shell Scripting
          • Variables
            • Command Substitution
            • Arguments
          • Reading User Input
          • if, else, and elif
          • BOOLEAN Logic
          • Loops
            • for Loops
            • while Loops
          • Functions
          • Local Vs Global Variables
          • Summary
        • Securing Linux
      • Windows
        • Security Hardening
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  1. Core Technical Skills
  2. Core Skills
  3. Linux
  4. Getting to Know Linux
  5. Navigating the Linux File System (LFS)

File Permissions and Ownership

PreviousListing Files and DirectoriesNextModifying Permissions with chmod

Last updated 1 year ago

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After you’ve worked with Linux for a while, it's almost inevitable that you'll bump into a "Permission Denied" message at some point. It's Linux's polite way of keeping order – preventing you from peeping into someone else's private files or inadvertently meddling with crucial system files.

Every file and directory has a set of nine permission bits, looking something like -rwxrwxrwx. These little guys dictate who can do what – read, write, or execute a file.

Here's a breakdown:

  • The first three bits apply to the owner’s permission

  • The next three apply to the group assigned to the file

  • The last three apply to everyone else

In this permission , the r stands for read, the w stands for write, and the x stands for execute permissions. If a dash appears in place of a letter, it means that permission is turned off for that associated read, write, or execution bit.

But here’s the twist: files and directories might be different beasts, but they share the same permission bits. The only difference is how these permissions play out for each. Let’s break down what each permission lets you do:

Permission

File

Folder

READ

View what's in the file

Permits listing the directory's contents

WRITE

Change the files contents, rename it, or delete it

Allows creating, deleting, or renaming files in the directory

EXECUTE

Run the file as a program

Permits accessing the directory and its contents

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