my-docs/Linux/Basic Administration/19-chmod-chown.md

📁 Linux File Permissions: A Quick & Clear Guide

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🔍 Example: Output of ls -lh

Run this command in your terminal:

ls -lh

Example output:

drwxr-xr-x 3 root root 4.0K Jul  1 22:22 dir1
-rw-r--r-- 1 root root 2.0G Jul  1 21:59 test2.tar

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🧠 Understanding the Output Columns

Column	Description
d / -	File type (d = directory, - = file)
rwxr-xr-x	Permissions (user, group, others)
3	Number of hard links
root	Owner (user)
root	Group
4.0K / 2.0G	File size
Jul 1 22:22	Last modification date
dir1 / test2.tar	File or directory name

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🔤 First Character: File Type Indicator

• d → Directory 📂
• - → Regular file 📄

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🔠 File Permissions Breakdown

drwxr-xr-x
│││ │ │ │
│││ │ │ └─ Permissions for Others (o)
│││ │ └── Permissions for Group (g)
│││ └──── Permissions for User (u)
│└──────── File type (d = directory, - = file)
└───────── Read (r), Write (w), Execute (x)

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🔐 Permission Symbols Explained

Symbol	Meaning
r	Read
w	Write
x	Execute

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👥 Permission Entities

Symbol	Meaning
u	User (owner)
g	Group
o	Others
a	All

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🔢 Numeric Permission Values (Octal)

Value	Binary	Permissions	Meaning
0	000	---	No permissions
1	001	--x	Execute only
2	010	-w-	Write only
3	011	-wx	Write + Execute
4	100	r--	Read only
5	101	r-x	Read + Execute
6	110	rw-	Read + Write
7	111	rwx	Read + Write + Execute

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🛠️ Changing Permissions with chmod

Syntax:

chmod [permissions] [filename]

Example (numeric):

chmod 755 myscript.sh

What does 755 mean?

Entity	Value	Permission
User	7	rwx (read, write, execute)
Group	5	r-x (read, execute)
Others	5	r-x (read, execute)

Recursive permission change:

chmod -R <permission> <directory>

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👑 Changing Ownership with chown

Syntax:

chown [options] owner[:group] file

Examples:

Change owner only:

sudo chown radin file.txt

Change owner and group:

sudo chown radin:dev file.txt

Change owner and group recursively (for directories):

sudo chown -R radin:dev files/