Task 1: Understanding File Permissions 📂🔍

Create a simple file and run ls -ltr to see the details of the files.

Each of the three permissions is assigned to three specific categories of users. The categories are:
- Owner: The person who owns the file or application. 👤
  - Use chown to change the ownership of a file or directory.
- Group: The group that owns the file or application. 👥
  - Use chgrp to change the group ownership of a file or directory.
- Others: All users who have access to the system, excluding those in the group. 🌐
  - Use chmod to change the permissions for other users on a file or directory.
Task: Change the user permissions of the file and note the changes after running ls -ltr. ✏️📄

a. Create a file and view details: 📄🔍


   touch myfile.txt  # Create a simple file
   ls -ltr myfile.txt  # View detailed permissions and metadata

You'll see an output like this:

-rw-r--r-- 1 user group 0 Oct 14 10:00 myfile.txt

First character (-): Indicates the file type (- for regular file, d for directory).
Next nine characters (rw-r--r--): Indicate permissions for owner, group, and others (in that order).
- r (read), w (write), x (execute).

b. Change ownership (chown): 🔄👤

sudo chown newuser myfile.txt  # Change the owner of the file to 'newuser'
ls -ltr myfile.txt  # Verify the changes

c. Change group ownership (chgrp): 🔄👥

sudo chgrp newgroup myfile.txt  # Change the group owner to 'newgroup'
ls -ltr myfile.txt  # Verify the changes

d. Change permissions (chmod): 🔧✨

codechmod 764 myfile.txt  # Owner: rwx, Group: rw, Others: r
ls -ltr myfile.txt  # Verify the changes

Task 2. Writing an Article:

Understanding Linux File Permissions 🐧

In Linux, file permissions control who can access or modify files and directories. Permissions are divided into three categories: owner, group, and others. Each category can have read (r), write (w), and execute (x) permissions. 🔐

Viewing Permissions 👀

You can view file permissions using the ls -l command📜:

codels -l myfile.txt

Output:

code-rw-r--r-- 1 user group 0 Oct 14 10:00 myfile.txt

-rw-r--r--: The first set of characters shows the permissions for owner, group, and others.
- rw-: Owner can read and write.
- r--: Group can read.
- r--: Others can read.

Changing Permissions 🔄🔐

Permissions can be modified using the chmod command:

Symbolic mode: ✨

    codechmod u+x myfile.txt  # Add execute permission for the owner

Numeric mode:🔢

  codechmod 764 myfile.txt  # Owner: rwx, Group: rw, Others: r

You can also change the ownership and group of a file:

chown: Change the owner. 👤🔄
```
  codesudo chown newuser myfile.txt
```
chgrp: Change the group. 👥🔄
```
  sudo chgrp newgroup myfile.txt
```

Special Permissions: Sticky Bit, SUID, and SGID

Sticky Bit: 🧷 Applied to directories to prevent users from deleting files they don’t own.
```
    codechmod +t /tmp/shared_directory
```
SUID: Allows a file to run with the owner's privileges. 🚀
```
  codechmod u+s /usr/bin/passwd
```
- SGID: Ensures new files in a directory inherit the directory's group. 📂👥
```
  codechmod g+s /mydir
```
  Task 3. Access Control Lists (ACL): 🔐
- a. Reading about ACL: Access Control Lists (ACL) provide more detailed control than standard permissions by allowing specific users or groups to have customized permissions for a file or directory. 📚
- b. Commands for ACL: 🛠️
  - View ACL (getfacl): 👀

        codegetfacl myfile.txt  # View ACL entries for the file

Set ACL (setfacl): ✍️

        codesudo setfacl -m u:username:rwx myfile.txt  # Grant 'username' full permissions
        sudo setfacl -m g:groupname:rx myfile.txt  # Grant 'groupname' read and execute permissions
        getfacl myfile.txt  # Verify ACL entries

c. Task:

Create a directory and apply ACL: 📂🔐

        codemkdir mydir  # Create directory
        sudo setfacl -m u:anotheruser:rwx mydir  # Give 'anotheruser' full access
        getfacl mydir  # Verify ACL permissions

Task 4. Additional Tasks:

a. Script to change permissions of multiple files: 📜🔧

  code#!/bin/bash
  echo "Enter the directory path:"
  read dir
  echo "Enter permission (e.g., 755):"
  read permission
  for file in $dir/*; do
    chmod $permission $file
    echo "Changed permissions of $file to $permission"
  done

Save this script as change_permissions.sh, make it executable:

        codechmod +x change_permissions.sh

b. Script to set ACL permissions based on user input: 🎛️📝

  code#!/bin/bash
  echo "Enter filename:"
  read filename
  echo "Enter username to set ACL:"
  read username
  echo "Enter permission for ACL (e.g., rwx):"
  read permission
  sudo setfacl -m u:$username:$permission $filename
  echo "Set ACL for $username with $permission on $filename"

Save this as set_acl.sh, and run it similarly to the other script.

Task 5. Sticky Bit, SUID, and SGID:

Sticky bit: 🧷 Ensures only the owner of a file (or root) can delete or rename it within a shared directory.
- Example:
  
  bash codemkdir /tmp/shared_directory chmod 1777 /tmp/shared_directory # Apply sticky bit
SUID (Set User ID): 🚀 When an executable with SUID is run, it executes with the permissions of the file's owner.
- Example:
```
  codesudo chmod u+s /usr/bin/passwd  # Example of an executable with SUID
```
SGID (Set Group ID): 🏷️ When SGID is set on a directory, new files inherit the directory's group.
- Example:
```
  codemkdir /tmp/sgid_test
  chmod g+s /tmp/sgid_test  # Apply SGID
```

Task: Demonstrate each with the above commands and explain the use cases.

Task 6. Backup and Restore Permissions: 🔄💾

a. Backup permissions: 🗄️✨

        code#!/bin/bash
        echo "Enter directory path:"
        read dir
        getfacl -R $dir > permissions_backup.txt
        echo "Permissions backed up to permissions_backup.txt"

b. Restore permissions: 🔄🛠️

        #!/bin/bash
        echo "Enter directory path:"
        read dir
        setfacl --restore=permissions_backup.txt
        echo "Permissions restored from permissions_backup.txt"

Save them as backup_permissions.sh and restore_permissions.sh, and make them executable as before.

Day 6 Task: File Permissions and Access Control Lists📃

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