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207 lines
2.4 KiB
Markdown
207 lines
2.4 KiB
Markdown
# Linux – Users & Ownership (Day 3)
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## What are Users in Linux?
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Linux is a multi-user system.
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Each file and process runs under a specific user.
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This prevents:
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- accidental damage
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- security issues
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- one app affecting another
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---
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## Why Users Matter in DevOps?
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Applications **never run as root** in production.
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Each service has its own user for safety.
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DevOps engineers:
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- create users
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- assign ownership
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- control access
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---
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## User Types
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- root → superuser (full access)
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- normal user → regular work
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- system user → runs services (nginx, docker)
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---
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## Check Current User
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```bash
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whoami
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```
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## View All Users
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```bash
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cat /etc/passwd
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```
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## Create a New User
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```bash
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sudo useradd devuser
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```
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## Set password:
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```bash
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sudo passwd devuser
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```
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## Switch User
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```bash
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su devuser
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```
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## Exit user
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```bash
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exit
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```
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## Groups in Linux
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Users belong to groups.
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Groups help manage permissions easily.
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## Check groups:
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```bash
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groups
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```
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## Add user to group:
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```bash
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sudo usermod -aG sudo devuser
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```
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## File Ownership
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Each file has:
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owner
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group
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## Check ownership:
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```bash
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ls -l
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```
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## Change Ownership (chown)
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```bash
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sudo chown devuser file.txt
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sudo chown devuser:devuser file.txt
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```
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## Change Group Only
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```bash
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sudo chgrp devuser file.txt
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```
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## Real DevOps Scenario
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Application folder:
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owned by app user
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not by root
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correct permissions
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Example:
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```bash
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sudo mkdir /var/myapp
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sudo chown devuser:devuser /var/myapp
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sudo chmod 755 /var/myapp
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```
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## Common Mistakes
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Running apps as root
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Wrong ownership causing permission denied
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Using sudo unnecessarily
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DevOps Rule
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❌ root everywhere
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✅ least privilege access
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## Exit user:
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```bash
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exit
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```
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## Groups in Linux
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Users belong to groups.
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Groups help manage permissions easily.
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## Check groups:
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groups
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## Add user to group:
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sudo usermod -aG sudo devuser
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## File Ownership
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Each file has:
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owner
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group
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## Check ownership:
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```bash
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ls -l
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```
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## Change Ownership (chown)
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```bash
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sudo chown devuser file.txt
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sudo chown devuser:devuser file.txt
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```
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## Change Group Only
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```bash
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sudo chgrp devuser file.txt
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```
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## Real DevOps Scenario
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Application folder:
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owned by app user
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not by root
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correct permissions
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Example:
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sudo mkdir /var/myapp
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sudo chown devuser:devuser /var/myapp
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sudo chmod 755 /var/myapp
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## Common Mistakes
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Running apps as root
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Wrong ownership causing permission denied
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Using sudo unnecessarily
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## DevOps Rule
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❌ root everywhere
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✅ least privilege access |