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208 lines
2.6 KiB
Markdown
208 lines
2.6 KiB
Markdown
# Linux – File Permissions (Day 2)
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## What are File Permissions?
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File permissions control **who can read, write, or execute** a file or folder in Linux.
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They protect the system from:
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- accidental deletion
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- unauthorized access
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- hacking
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---
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## Why Permissions are Important for DevOps?
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DevOps engineers manage **live servers**.
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Wrong permissions can:
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- break applications
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- expose data
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- allow hackers access
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So permissions are **critical**.
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---
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## Permission Types
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There are 3 permissions:
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- r → read
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- w → write
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- x → execute
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---
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## Permission Groups
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Permissions are set for 3 types of users:
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- u → user (owner)
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- g → group
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- o → others
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Order is always:
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## user | group | others
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---
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## Checking Permissions
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```bash
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ls -l
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-rwxr-xr--
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Meaning:
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user → rwx
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group → r-x
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others → r--
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Add values to set permissions.
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Examples:
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7 = rwx (4+2+1)
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6 = rw- (4+2)
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5 = r-x (4+1)
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4 = r--
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```
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---
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## Setting Permissions
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```bash
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chmod 755 file.txt
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```
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Meaning:
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user → 7 (rwx)
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group → 5 (r-x)
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others → 5 (r-x)
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## Symbolic Method
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```bash
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chmod u+x file.sh
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chmod g-w file.sh
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chmod o+r file.sh
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```
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## Common Permission Examples
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```bash
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chmod 755 file.txt
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chmod 644 file.txt
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chmod 777 file.txt
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chmod 666 file.txt
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chmod 700 file.txt
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chmod 600 file.txt
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```
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## Execute Permission (Very Important)
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To run a script:
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```bash
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./script.sh
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```
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If permission denied:
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```bash
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chmod +x script.sh
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```
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## Folder Permissions Rule
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```bash
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r → list files
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w → create/delete files
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x → enter folder
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```
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Without x, you cannot cd into folder.
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## Execute Permission (Very Important)
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To run a script:
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```bash
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./script.sh
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```
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If permission denied:
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```bash
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chmod +x script.sh
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```
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## Folder Permissions Rule
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```bash
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r → list files
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w → create/delete files
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x → enter folder
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```
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Without x, you cannot cd into folder.
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## Mini Practice Task
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```bash
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mkdir test
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touch test/app.sh
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ls -l test
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chmod 755 test/app.sh
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ls -l test
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```
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## Common Mistakes
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- Giving 777 permissions (very dangerous)
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- Not understanding folder execute permission
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- Changing permissions blindly on production servers
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## Changing Ownership
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To change the owner of a file:
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```bash
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sudo chown username file.txt
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```
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To change both owner and group:
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```bash
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sudo chown username:groupname file.txt
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```
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To change the group ownership:
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```bash
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sudo chgrp groupname file.txt
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```
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## Recursive Changes
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Apply permissions or ownership to a directory and all its contents:
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```bash
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chmod -R 755 folder_name/
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chown -R username:groupname folder_name/
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```
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## Checking Current Permissions
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To see detailed permissions for all files in a directory:
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```bash
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ls -la
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```
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