mirror of
https://github.com/thecyberlearn/devops-notes.git
synced 2026-08-18 09:32:51 +00:00
164 lines
2.1 KiB
Markdown
164 lines
2.1 KiB
Markdown
# Linux – SSH & Remote Server Access (Day 5)
|
||
|
||
## What is SSH?
|
||
SSH (Secure Shell) is used to securely connect to a remote server.
|
||
DevOps engineers use SSH daily to manage cloud servers.
|
||
|
||
---
|
||
|
||
## Why SSH is Important for DevOps?
|
||
- Access cloud servers (AWS EC2, VPS)
|
||
- Deploy applications
|
||
- Debug production issues
|
||
- Manage configurations
|
||
|
||
No SSH = no DevOps work.
|
||
|
||
---
|
||
|
||
## Basic SSH Syntax
|
||
```bash
|
||
ssh user@server_ip
|
||
```
|
||
|
||
Example:
|
||
```bash
|
||
ssh ubuntu@13.234.56.78
|
||
```
|
||
|
||
---
|
||
|
||
## Default SSH Port
|
||
- Port 22
|
||
|
||
Custom port example:
|
||
```bash
|
||
ssh -p 2222 user@server_ip
|
||
```
|
||
|
||
---
|
||
|
||
## SSH First-Time Connection
|
||
You may see:
|
||
```
|
||
Are you sure you want to continue connecting (yes/no)?
|
||
```
|
||
|
||
Type:
|
||
```text
|
||
yes
|
||
```
|
||
|
||
---
|
||
|
||
## SSH Key-Based Authentication (VERY IMPORTANT)
|
||
|
||
Instead of passwords, DevOps uses SSH keys.
|
||
|
||
Benefits:
|
||
- More secure
|
||
- No password typing
|
||
- Required by cloud providers
|
||
|
||
---
|
||
|
||
## Generate SSH Key
|
||
```bash
|
||
ssh-keygen
|
||
```
|
||
|
||
Press Enter for defaults.
|
||
|
||
This creates:
|
||
- private key → ~/.ssh/id_rsa
|
||
- public key → ~/.ssh/id_rsa.pub
|
||
|
||
---
|
||
|
||
## Copy SSH Key to Server
|
||
```bash
|
||
ssh-copy-id user@server_ip
|
||
```
|
||
|
||
Or manually copy:
|
||
```bash
|
||
cat ~/.ssh/id_rsa.pub
|
||
```
|
||
|
||
Paste into server:
|
||
```bash
|
||
~/.ssh/authorized_keys
|
||
```
|
||
|
||
---
|
||
|
||
## Login Using SSH Key
|
||
```bash
|
||
ssh user@server_ip
|
||
```
|
||
|
||
(No password needed)
|
||
|
||
---
|
||
|
||
## SSH Config File (PRO TIP)
|
||
Create:
|
||
```bash
|
||
~/.ssh/config
|
||
```
|
||
|
||
Example:
|
||
```text
|
||
Host myserver
|
||
HostName 13.234.56.78
|
||
User ubuntu
|
||
IdentityFile ~/.ssh/id_rsa
|
||
```
|
||
|
||
Now connect using:
|
||
```bash
|
||
ssh myserver
|
||
```
|
||
|
||
---
|
||
|
||
## Common SSH Commands
|
||
```bash
|
||
exit # logout
|
||
whoami # check user
|
||
hostname # server name
|
||
uptime # server running time
|
||
```
|
||
|
||
---
|
||
|
||
## Common SSH Errors
|
||
- Permission denied
|
||
- Wrong user
|
||
- Wrong key
|
||
- Port blocked by firewall
|
||
|
||
---
|
||
|
||
## DevOps Best Practices
|
||
- Disable password login
|
||
- Use key-based auth only
|
||
- Never share private key
|
||
- Use least privilege users
|
||
|
||
---
|
||
|
||
## Real DevOps Scenario
|
||
1. Create EC2 instance
|
||
2. SSH into server
|
||
3. Install Docker
|
||
4. Deploy application
|
||
|
||
SSH is the entry point.
|
||
|
||
---
|
||
|
||
## Summary
|
||
Today I learned SSH basics, key-based authentication,
|
||
and how DevOps engineers securely connect to remote servers.
|