Linux Essentials for Cloud — Part 1

Basic Linux you need to know to get started in Cloud.

Hi—this is Kisan from The Cloud Handbook. Each week I share about Cloud, DevOps, System Design deep dives and technologies around it. If you have not subscribed yet, you can subscribe here.

This is the Part 1 of the Linux Essential for Cloud series. There will be 3 parts where I will share the essential Linux knowledge and skill you will need in Cloud.

Let’s get started.

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1. Linux Basics

Linux is an open-source, Unix-like operating system.

From official Linux.com website:

Just like Windows, iOS, and Mac OS, Linux is an operating system. In fact, one of the most popular platforms on the planet, Android, is powered by the Linux operating system. An operating system is software that manages all of the hardware resources associated with your desktop or laptop. To put it simply, the operating system manages the communication between your software and your hardware. Without the operating system (OS), the software wouldn’t function.

Linux kernel source code can be found at: https://www.kernel.org/

In cloud computing, Linux dominates for several key reasons:

Cost Effectiveness: No licensing fees make it ideal for large-scale deployments where hundreds or thousands of instances might be running simultaneously.

Performance and Resource Efficiency: Linux's lightweight nature means more resources are available for applications rather than the operating system overhead.

Security and Stability: The open-source nature allows for rapid security patches, and Linux systems can run for months without requiring restarts.

Containerization Ready: Linux provides native support for containers through features like namespaces and cgroups, making it the natural choice for Docker and Kubernetes deployments.

Automation Friendly: Linux's command-line interface and scripting capabilities make it perfect for Infrastructure as Code and automation workflows.

Linux Distributions Commonly Used in the Cloud

Ubuntu: The most popular choice for cloud deployments, especially for development and web applications. Ubuntu's Long Term Support (LTS) versions provide 5 years of security updates, making them ideal for production environments.

Amazon Linux: AWS's own distribution, optimized for EC2 instances. It comes pre-configured with AWS CLI tools and is tuned for optimal performance on AWS infrastructure.

Red Hat Enterprise Linux (RHEL): Enterprise-grade distribution favored by large organizations. Provides commercial support and is known for stability and security.

CentOS/Rocky Linux: Community-driven alternatives to RHEL, offering similar features without licensing costs. Popular for enterprise environments that need RHEL compatibility.

Alpine Linux: Ultra-lightweight distribution (typically 5MB base image) commonly used for containers and microservices due to its minimal attack surface.

Debian: Known for stability and security, often used as a base for other distributions. Popular for servers that need long-term reliability.

Distrowatch.com

There are tens of thousands of Linux distros available today. You can learn more about distros at https://distrowatch.com/dwres.php?resource=popularity

Using SSH to Connect to Linux Servers

SSH (Secure Shell) is the primary method for connecting to Linux servers in the cloud. Understanding SSH is fundamental for cloud engineers.

Basic SSH Connection:

ssh username@server-ip-address
ssh ubuntu@192.168.1.100

Using SSH Keys (Recommended): SSH keys provide more security than passwords. Cloud providers typically use key-based authentication by default.

# Generate an SSH key pair
ssh-keygen -t rsa -b 4096 -C "your-email@example.com"

# Connect using a specific private key
ssh -i /path/to/private-key username@server-ip
ssh -i ~/.ssh/aws-key.pem ubuntu@ec2-instance-ip

SSH Configuration File: Create ~/.ssh/config to simplify connections:

Host web-server
    HostName 192.168.1.100
    User ubuntu
    IdentityFile ~/.ssh/web-server-key.pem
    Port 22

SSH Security Best Practices:

• Disable password authentication

• Change default SSH port from 22

• Regularly rotate SSH keys

• Disable root login over SSH

The video tutorial below explains everything you need to know about SSH if you are still confused.

Terminal Essentials and Shell Overview

The shell is your primary interface for interacting with Linux systems. Understanding shell basics is crucial for cloud operations.

Bash (Bourne Again Shell): The default shell on most Linux distributions. Provides command history, tab completion, and extensive scripting capabilities.

Zsh (Z Shell): Popular alternative shell with enhanced features like better tab completion, spell correction, and theme support.

Essential Shell Concepts:

• Command Prompt: Shows current user, hostname, and working directory

• Command History: Access previous commands with up arrow or history command

• Tab Completion: Press Tab to auto-complete commands and file names

• Pipes and Redirection: Combine commands and redirect output

• Environment Variables: Store configuration and system information

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2. Basic Linux Commands

You will use this basic commands frequently. So, understand this commands and what they do.

• File and directory navigation: ls, cd, pwd, tree

• File operations: cp, mv, rm, mkdir, touch

• Viewing and editing files: cat, less, more, head, tail, nano, vim

• Permissions and ownership: chmod, chown, ls -l, umask

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3. Permissions and Ownership

Linux permissions are crucial for security, especially in cloud environments where multiple users and services interact.

Permission Types:

• r (read): Permission to read file contents or list directory

• w (write): Permission to modify file or create/delete files in directory

• x (execute): Permission to run file as program or enter directory

chmod - Change Permissions:

chmod 755 script.sh                 # rwxr-xr-x (owner: rwx, group: r-x, others: r-x)
chmod +x script.sh                  # Add execute permission for all
chmod u+w file.txt                  # Add write permission for owner
chmod go-r file.txt        # Remove read permission for group and others
chmod -R 644 /var/www/html/         # Recursively set permissions

Common Permission Patterns:

• 644: Files (owner: rw-, group: r--, others: r--)

• 755: Directories and executables (owner: rwx, group: r-x, others: r-x)

• 600: Private files (owner: rw-, group: ---, others: ---)

• 700: Private directories (owner: rwx, group: ---, others: ---)

chown - Change Ownership:

chown user:group file.txt           # Change owner and group
chown user file.txt                 # Change only owner
chown :group file.txt               # Change only group
chown -R user:group directory/      # Recursively change ownership

ls -l - View Detailed File Information:

ls -l                          # Show permissions, ownership, size, date
ls -la                         # Include hidden files

If you are still confused, you can watch this tutorial here.

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3. Process and Resource Management

• Checking system usage: top, htop, free, uptime

• Managing processes: ps, kill, killall, nice, renice

• Background jobs: &, jobs, fg, bg, nohup

Checking System Usage

top - Real-time System Monitor:

$ top                                 # Interactive process viewer
                                    # Press 'q' to quit, 'k' to kill process, '1' to show all CPU cores

htop - Enhanced Process Viewer:

$ htop                                # More user-friendly than top
# Use arrow keys to navigate, F9 to kill, F10 to quit

free - Memory Usage:

$ free                                # Show memory usage in KB
$ free -h                             # Human-readable format (MB/GB)
$ free -s 5                           # Update every 5 seconds

uptime - System Load and Uptime:

$ uptime                              # Show uptime and load averages
# Load averages: 1-minute, 5-minute, 15-minute

Managing Processes

ps - List Running Processes:

ps                                  # Show processes for current user
ps aux                              # Show all processes with detailed info
ps -ef                              # Show all processes in different format
ps -C nginx                         # Show processes by command name

kill and killall - Terminate Processes:

kill 1234                           # Kill process by PID
kill -9 1234                        # Force kill (SIGKILL)
kill -15 1234                       # Graceful termination (SIGTERM)
killall nginx                       # Kill all processes named nginx
killall -9 nginx                    # Force kill all nginx processes

nice and renice - Process Priority:

nice -n 10 command                  # Start command with priority 10
renice -10 1234                     # Change priority of existing process
# Priority range: -20 (highest) to 19 (lowest)

Background Jobs

Running Commands in Background:

command &                           # Run command in background
nohup command &                     # Run command immune to hangups

Job Control:

jobs                                # List active jobs
fg %1                               # Bring job 1 to foreground
bg %1                               # Send job 1 to background
disown %1 

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Conclusion

Basic Linux Commands, Process management, Permissions, ssh are non negotiable skills while you are getting started in cloud. You will require these concepts at work frequently.

In the Part II of this series, we will be talking about

• File System and Storage

• Users, Groups and Permissions

• Package Management

• System Logs and Troubleshooting

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