User and Privileges.md

Users and Privileges

File Permissions

Here we can see the highlighted portion. This posrtion tells the user permissions for each file. Lets break the highlighted portion down:

drwxr-xr-x

Here:

• d denotes that the current folder is a directory
• r stands for read access
• w stands for write access
• x stands for execute access

Permissions For Users

Now lets see what our user (kali) and other user on this machine have permissions for the highligted folder called Documents

Reading from left to right we know that d stands for directory.

After that the permissions are listed.

• The first permissions are of the owner of the file (which is in this case kali):

  rwx denotes that the kali user has all three read, write and execute permission on this directory

• After that we have the permission for the group users:

  r-x meaning that the group user only has the read and execute permissions not the write permission

• Lastly we have the third settings for all users:

  r-x meaning that both read and execute only and no write access

Granting Permissions Through The chmod Command

Here we have created a file named hello.txt through the echo command. On viewing the permissions we come to know that our current user and owner of this file has only read and write but no execute permissions for this file.

In order to change this permissions we use the chmod command. There are two ways of doing it:

• Method 1: Symbolic Mode

  

  Here we used the following command syntax: chmod +<permissions> <filename>

• Method 2: Numeric Mode

  

  Here we have used the following command: chmod <numeric_permissions> <filename>

  Each permission (read, write, execute) is represented by a digit:

  • Read = 4

  • Write = 2

  • Execute = 1

  Example:

  For example:

  chmod 755 hello.txt

  This gives:

  • Owner: read + write + execute (7)

  • Group: read + execute (5)

  • Others: read + execute (5)

Below are the tables for easier understanding of these representations:

🔐 Permission Values Table

Symbol	Permission	Binary	Value	Description
r	Read	100	4	View file contents / list directory
w	Write	010	2	Modify file / create-delete in dir
x	Execute	001	1	Run file as program / enter directory
-	No perm	000	0	No permission

---

🔢 Numeric Permission Examples (for chmod)

Command	Owner	Group	Others	Meaning
chmod 777 file	rwx	rwx	rwx	Full access for everyone
chmod 755 file	rwx	r-x	r-x	Owner full, others can read & execute
chmod 700 file	rwx	---	---	Only owner has full access
chmod 644 file	rw-	r--	r--	Owner can read/write, others can only read
chmod 600 file	rw-	---	---	Only owner can read and write

Adding A User

Command

sudo adduser <name>

Switching Users

su <username>

Here we have created a user named John and switched from user kali to john using the su command

grep Command

grep "<word>" <filename/path>