DEV Community: Aryan Vaishnani

Shell Basics (Bash, Zsh, Sh)

Aryan Vaishnani — Mon, 25 May 2026 07:36:39 +0000

A shell is a command-line interpreter that allows users to interact with the Linux operating system.

The shell:

Accepts commands
Executes programs
Manages scripts
Handles automation
Controls system operations

What is a Shell?

When you type a command like:

ls

The shell:

Reads the command
Finds the executable
Executes it
Displays output

Common Linux Shells:

Shell	Full Name	Main Usage
sh	Bourne Shell	Original Unix shell
bash	Bourne Again Shell	Most common Linux shell
zsh	Z Shell	Advanced interactive shell

1. Sh (Bourne Shell)

About

One of the oldest Unix shells
Created for early Unix systems
Lightweight and simple

Features

Basic scripting
POSIX compatible
Minimal functionality

Location

/bin/sh

Usage

sh script.sh

2. Bash (Bourne Again Shell)

About

Most widely used Linux shell.

Default shell in many Linux distributions.

Bash

Features of Bash

Command history
Tab completion
Variables
Scripting support
Aliases
Job control
Pipes and redirection

Check Current Shell

echo $SHELL

Bash Configuration Files

File	Purpose
~/.bashrc	Interactive shell config
~/.bash_profile	Login shell config
/etc/bashrc	Global bash config

3. Zsh (Z Shell)

About

Advanced shell with better user experience and customization.

Features of Zsh

Better auto-completion
Smart suggestions
Advanced themes
Plugin support
Better productivity

Install Zsh

Ubuntu/Debian

sudo apt install zsh -y

Change Default Shell to Zsh

chsh -s $(which zsh)

Logout and login again.

Zsh Configuration File

~/.zshrc

Install Oh My Zsh

Popular Zsh framework.

Oh My Zsh Official Website

Install:

sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

Real-World Zsh Plugins

Git Plugin

Edit:

nano ~/.zshrc

Add:

plugins=(git docker kubectl)

Reload:

source ~/.zshrc

Real-World Practical Example

DevOps Engineer Shell Setup

A DevOps engineer managing:

Docker
Kubernetes
Git
Cloud servers

Usually configures shell for faster operations.

Practical Bash Example

Create Productivity Aliases

Edit:

nano ~/.bashrc

Add:

alias k='kubectl'
alias d='docker'
alias dc='docker compose'
alias gs='git status'
alias gp='git pull'
alias tf='terraform'

Reload:

source ~/.bashrc

Now commands become:

k get pods
d ps
gs
tf apply

This is heavily used in:

DevOps
Cloud engineering
Kubernetes administration
Linux server management

Useful Shell Commands

View Current Shell

echo $0

List Available Shells

cat /etc/shells

Switch Shell Temporarily

bash
zsh
sh

Shell Scripting Example

Simple Script

Create:

nano backup.sh

Add:

!/bin/bash

echo "Backup Started"
tar -czf backup.tar.gz /home/user/data
echo "Backup Completed"

Run:

chmod +x backup.sh

./backup.sh

Real-World Usage

Area	Common Shell
Linux servers	Bash
DevOps	Bash + Zsh
Automation	Bash
CI/CD pipelines	Sh/Bash
Kubernetes management	Zsh/Bash
Cloud administration	Bash

Getting Help (man pages, info, --help)

Aryan Vaishnani — Mon, 25 May 2026 07:26:08 +0000

Linux provides built-in help systems to learn commands, options, and usage.

The most common help methods are:

man pages
info pages
--help option

1. man Pages

What is man?

man stands for manual pages.

It provides detailed documentation for Linux commands, system calls, configuration files, and utilities.

Basic Syntax

man command_name

Example:

man ls

This opens the manual page for the ls command.

Sections in man Pages

Section	Description
NAME	Command name and purpose
SYNOPSIS	Command syntax
DESCRIPTION	Detailed explanation
OPTIONS	Available flags/options
EXAMPLES	Usage examples
SEE ALSO	Related commands

Important man Navigation Keys

Key	Action
Arrow Up/Down	Scroll
Space	Next page
/word	Search word
n	Next search result
q	Quit

Search man Pages

Search by Keyword

man -k network

Equivalent to:

apropos network

Short Description Only

whatis ls

2. info Pages

What is info?

info provides more detailed and structured documentation than man.

It supports:

Navigation menus
Hyperlink-like structure
Detailed GNU documentation

Basic Syntax

info command_name

Example:

info bash

info ls or info pwd

Features of info

Detailed explanations
Node-based navigation
Better for large documentation

Navigation Keys in info

Key	Action
Arrow Keys	Move
Enter	Open node
u	Go up
n	Next node
p	Previous node
q	Quit

3. --help Option

Most Linux commands provide quick help using:

command --help

Example:

ls --help

Purpose of --help

Shows:

Command syntax
Options
Short explanations

Advantages of --help

Fast and simple
No manual navigation needed
Good for quick reference

Locate Command Documentation

whereis bash

View Command Path

which python

Basic Boot Process

Aryan Vaishnani — Mon, 25 May 2026 07:21:48 +0000

Basic Boot Process in Linux

The boot process is the sequence of steps that happens when a computer starts until the Linux operating system becomes ready for use.

1. Power On

User presses the power button.
CPU starts executing firmware instructions stored on motherboard.

2. BIOS or UEFI

BIOS

Basic Input Output System

UEFI

Unified Extensible Firmware Interface

These firmware systems:

Check hardware components
Detect CPU, RAM, disks, keyboard
Perform POST (Power-On Self Test)
Find bootable device

POST (Power-On Self Test)

Checks:

RAM
CPU
Storage devices
Keyboard and peripherals

If hardware fails, system may show error beeps or messages.

3. Bootloader Stage

The bootloader loads the Linux kernel into memory.

Most Linux systems use:

GNU GRUB

Responsibilities of GRUB

Shows boot menu
Select operating system
Loads Linux kernel
Loads initramfs/initrd

GRUB Configuration Location

Common files:

/boot/grub/

/boot/grub2/

Main config:

grub.cfg

4. Linux Kernel Loading

After GRUB:

Linux kernel loads into RAM
Kernel initializes hardware
Drivers are loaded
Root filesystem is mounted

Kernel file example:

vmlinuz

initramfs / initrd

Temporary filesystem loaded during boot.

Purpose:

Load required drivers
Prepare root filesystem
Help kernel access storage devices

5. Init/Systemd Process

After kernel initialization, the first userspace process starts.

Traditionally:

init

Modern Linux systems mainly use:

systemd

Process ID:

PID 1

Responsibilities of systemd/init

Start system services
Mount filesystems
Configure networking
Start login services
Manage system targets/runlevels

5. Starting Services

System services start in background.

Examples:

SSH server
Network manager
Database services
Docker daemon
Web servers

Example:

sshd
docker
nginx

6. Login Screen or Shell

Finally system provides:

GUI login screen
Terminal login shell

User enters:

Username
Password

System becomes ready for use.

Linux Boot Flow Diagram

Power On
↓
BIOS / UEFI
↓
POST Check
↓
Bootloader (GRUB)
↓
Linux Kernel
↓
initramfs/initrd
↓
systemd/init
↓
Services Start
↓
Login Screen / Shell

Important Boot Files

File/Component	Purpose
BIOS/UEFI	Hardware initialization
GRUB	Bootloader
vmlinuz	Linux kernel
initramfs	Temporary boot filesystem
systemd	Service manager
/boot	Boot files directory

Common Commands Related to Boot

Check Current Kernel

uname -r

View Boot Logs

journalctl -b

Check Running Services

systemctl list-units --type=service

Check Default Target

systemctl get-default

Common Boot Problems

Corrupted GRUB
Missing kernel files
Filesystem corruption
Failed services
Wrong fstab configuration
Kernel panic

Kernel Panic

A critical kernel error where the system cannot continue booting.

Causes:

Driver failures
Hardware problems
Corrupted kernel
Memory issues

Installing Linux (VM & Bare Metal)

Aryan Vaishnani — Mon, 25 May 2026 07:15:03 +0000

Linux can be installed in two main ways:

Virtual Machine (VM) Installation
Bare Metal Installation

Requirements for VM Installation

ISO image of Linux distribution
Virtualization software
Minimum RAM and storage

Popular VM Software

Oracle VM VirtualBox
VMware Workstation
Microsoft Hyper-V

Steps to Install Linux in VM

Step 1: Download Linux ISO

Download ISO from official website.

Examples:

Step 2: Install Virtualization Software

Install:

VirtualBox
VMware
Hyper-V

Step 3: Create New Virtual Machine

Configure:

VM name
RAM allocation
CPU cores
Disk size
ISO file selection

Example:

RAM: 4 GB
Disk: 25 GB

Step 4: Start VM

Boot VM using Linux ISO.

Linux installer screen will appear.

Step 5: Install Linux

Typical installation steps:

Select language
Select keyboard layout
Configure disk partition
Create username and password
Install bootloader
Start installation

Step 6: Reboot VM

After installation:

Remove ISO
Restart VM
Login to Linux system

Advantages of VM Installation

Safe testing environment
No risk to host OS
Easy snapshots and backups
Multiple OS support
Good for learning DevOps and Kubernetes

Disadvantages of VM Installation

Lower performance than physical installation
Shares hardware resources
Limited graphics performance

Bare Metal Linux Installation

Bare metal means installing Linux directly on physical hardware.

Linux gets full access to:

CPU
RAM
Storage
Network devices

Requirements for Bare Metal Installation

Linux ISO
USB drive (8 GB or more)
Bootable USB creation tool

Tools to Create Bootable USB

Rufus
balenaEtcher
Ventoy

Steps for Bare Metal Installation

Step 1: Download Linux ISO

Download preferred Linux distribution ISO.

Step 2: Create Bootable USB

Use:

Rufus
Etcher
Ventoy

Select:

ISO file
USB drive
Start flashing

Step 3: Boot from USB

Insert USB
Restart computer
Open BIOS/UEFI boot menu
Select USB device

Step 4: Start Linux Installer

Linux installer menu will appear.

Options:

Try Linux
Install Linux

Step 5: Configure Installation

Choose:

Language
Timezone
Keyboard layout
Disk partitioning
Username/password

Partition Types

Partition	Purpose
/	Root filesystem
/home	User files
swap	Virtual memory
/boot	Boot files

Step 6: Install Bootloader

Usually:

GRUB bootloader is installed automatically.

GNU GRUB

Step 7: Complete Installation

Installation copies files
System reboots
Remove USB drive
Login to Linux

Advantages of Bare Metal Installation

Full hardware performance
Better speed
Better GPU and disk performance
Suitable for production systems

Disadvantages of Bare Metal Installation

Risk of data loss if partitioned incorrectly
Harder to test multiple systems
Less flexible than VMs

VM vs Bare Metal

VM Installation	Bare Metal Installation
Runs inside host OS	Runs directly on hardware
Easier for learning	Better performance
Safe testing	Production-ready
Resource sharing	Full hardware access
Easy snapshots	More complex recovery

Real-World Usage

VM Usage

Learning Linux
DevOps practice
Kubernetes labs
Testing applications

Bare Metal Usage

Production servers
Gaming systems
Database servers
High-performance workloads

Virtualization & Cloud Basics

Aryan Vaishnani — Mon, 25 May 2026 07:10:06 +0000

What is Virtualization?

Virtualization is a technology that allows multiple virtual machines (VMs) to run on a single physical computer.

It creates a virtual version of:

Servers
Operating systems
Storage
Networks
Applications

Using virtualization, one physical server can run many independent systems.

Virtual Machine (VM)

A Virtual Machine is a software-based computer that behaves like a real computer.

Each VM has:

Operating system
CPU allocation
Memory allocation
Storage
Network settings

Example:

One physical server can run:
- Ubuntu VM
- Windows VM
- CentOS VM

Hypervisor

A Hypervisor is software that creates and manages virtual machines.

It allows multiple VMs to share hardware resources.

Types of Hypervisors

1. Type 1 Hypervisor (Bare Metal)

Runs directly on hardware.

Features

Better performance
High security
Used in data centers

Examples

VMware ESXi
Microsoft Hyper-V
Xen

2. Type 2 Hypervisor (Hosted)

Runs on top of an operating system.

Features

Easy to use
Good for learning and testing

Examples

Oracle VM VirtualBox
VMware Workstation

Benefits of Virtualization

Better hardware utilization
Reduced infrastructure cost
Faster server deployment
Easy backup and recovery
Isolation between systems
Easy scaling
Supports cloud computing

What is Cloud Computing?

Cloud computing means delivering computing services over the internet.

Instead of owning physical servers, users rent resources like:

Servers
Storage
Databases
Networking
Software
Computing power

Characteristics of Cloud Computing

On-demand access
Pay-as-you-use
Scalability
High availability
Remote access
Automation

Types of Cloud Deployment

1. Public Cloud

Cloud services shared over the internet.

Examples

Amazon Web Services
Microsoft Azure
Google Cloud

Advantages

Low cost
Easy scaling
No hardware management

2. Private Cloud

Cloud infrastructure dedicated to one organization.

Advantages

Better control
More security
Custom configurations

3. Hybrid Cloud

Combination of public and private cloud.

Advantages

Flexibility
Better workload distribution
Improved disaster recovery

Cloud Service Models

1. IaaS (Infrastructure as a Service)

Provides virtual infrastructure.

Examples

Virtual machines
Storage
Networks

Example Providers

Amazon Web Services EC2
Microsoft Azure Virtual Machines

2. PaaS (Platform as a Service)

Provides platform for application development.

Features

No server management
Easy deployment

Examples

Google Cloud App Engine
Heroku

3. SaaS (Software as a Service)

Provides ready-to-use software over internet.

Examples

Google Workspace
Microsoft 365
Zoom

Difference Between Virtualization and Cloud

Virtualization	Cloud Computing
Creates virtual machines	Delivers services over internet
Technology	Service model
Runs on physical hardware	Uses virtualization internally
Focus on resource sharing	Focus on service delivery

Linux Kernel vs User Space

Aryan Vaishnani — Mon, 25 May 2026 07:03:31 +0000

Linux operating system is mainly divided into two parts:

Kernel Space
User Space

Both work together to run the operating system.

Linux Kernel

The kernel is the core part of the Linux operating system.

It directly interacts with the computer hardware and manages system resources.

Main Responsibilities of Kernel

Process management
Memory management
Device management
File system management
CPU scheduling
Security and permissions
Network management

Characteristics

Runs in privileged mode
Has full hardware access
Very critical for system stability
Handles communication between hardware and software

Examples of Kernel Components

Device drivers
Scheduler
Memory manager
Network stack
File system manager

User Space

User space is the area where user applications and programs run.

Applications cannot directly access hardware. They use system calls to communicate with the kernel.

Main Responsibilities of User Space

Running applications
User interaction
Executing commands
Managing graphical interfaces
Running background services

Characteristics

Runs with limited permissions
Safer than kernel space
Application crash usually does not crash the whole system
Depends on kernel services

Examples of User Space Programs

Bash
Firefox
Apache HTTP Server
Docker
Text editors and terminal programs

Communication Between Kernel and User Space

Applications in user space communicate with the kernel using:

System calls
APIs
Libraries

Example:

When a user opens a file:
- User application sends request
- Kernel accesses disk
- Kernel returns data to application

System Call Example

When using command:

cat file.txt

Process:

cat runs in user space
It requests file access through system calls
Kernel reads the file from storage
Data is returned to user space
Output is displayed on terminal

Difference Between Kernel Space and User Space

Kernel Space	User Space
Core part of OS	Area for applications
Direct hardware access	No direct hardware access
Runs in privileged mode	Runs in restricted mode
High risk if crashed	Safer if application crashes
Manages system resources	Uses system resources
Faster hardware operations	Depends on kernel services

Open Source Philosophy

Aryan Vaishnani — Mon, 25 May 2026 06:44:17 +0000

Open source means the source code of software is publicly available. Anyone can:

View the code
Modify the code
Share the code
Improve the software

The main goal of open source is collaboration, transparency, learning, and freedom in software development.

Principles of Open Source

1.Freedom to Use

Users can run the software for any purpose.

2.Freedom to Study

Users can study how the software works.

3.Freedom to Modify

Users can change the software according to their needs.

4.Freedom to Share

Users can distribute original or modified versions.

Benefits of Open Source

Free to use
Community-driven development
Faster innovation
Better security through transparency
No vendor lock-in
Large developer community
Good for learning and research

Open Source Licenses

An open-source license defines how software can be used, modified, and distributed.

GPL License

Full Form

GNU General Public License

Developed By

Richard Stallman and the Free Software Foundation

Main Idea

GPL is a strong copyleft license.

If someone modifies GPL software and distributes it, they must also release their modified source code under the GPL license.

Features

Source code must remain open
Modified versions must also be open source
Users have freedom to modify and share
Prevents proprietary conversion

Advantages

Keeps software free forever
Encourages community contribution
Protects user freedom

Disadvantages

Strict rules for commercial companies
Some companies avoid GPL because they must share modifications

Examples

Linux kernel
WordPress
GIMP

2.MIT License

Developed By

Massachusetts Institute of Technology

Main Idea

MIT is a permissive open-source license with very few restrictions.

People can use, modify, and distribute the software even in commercial products.

Features

Very simple license
Allows commercial use
Allows private modifications
Does not require releasing modified source code

Advantages

Easy to use
Business-friendly
Maximum flexibility
Popular in startups and web development

Disadvantages

Modified software can become closed source
Less protection for open-source freedom

Examples

React
jQuery
Ruby on Rails

3.Apache License

Developed By

Apache Software Foundation

Main Idea

Apache License is a permissive license like MIT but includes patent protection.

Features

Allows commercial use
Allows modification and distribution
Includes patent rights protection
Can be used in proprietary software

Advantages

Business-friendly
Patent safety
Flexible and modern
Good for enterprise software

Disadvantages

Slightly more complex than MIT
Does not force modifications to stay open source

Examples

Apache HTTP Server
Kubernetes
Apache Hadoop

Linux Distributions

Aryan Vaishnani — Mon, 25 May 2026 06:39:43 +0000

A Linux distribution (Linux distro) is an operating system made using the Linux kernel along with software packages, package managers, and system tools.

Different distributions are designed for different purposes such as servers, desktops, security testing, cloud computing, or development.

Red Hat Enterprise Linux (RHEL)

Developed by Red Hat

Enterprise-grade Linux distribution

Mainly used in:

Large companies
Data centers
Cloud environments
Enterprise servers

Very stable and secure

Paid subscription-based support

Uses RPM package format

Package manager – yum and dnf.

Features

High security
Long-term support
Certified for enterprise applications
Stable updates
Popular in DevOps and cloud

Best For

Production servers
Enterprise infrastructure
Corporate environments

2.CentOS

Community version based on RHEL

Free and open-source

Used widely for servers before CentOS Stream changes

Very similar to RHEL

Features

Stable system
Free alternative to RHEL
Good for server environments
Enterprise-like experience

Best For

Learning RHEL
Hosting servers
Testing environments

Note

Traditional CentOS Linux was discontinued and replaced by CentOS Stream.

3.Ubuntu

Developed by Canonical

Based on Debian

One of the most popular Linux distributions

Features

Beginner-friendly
Large community support
Easy software installation
Regular updates
Strong cloud and container support

Package Manager

Best For

Beginners
Developers
Cloud servers
Desktop users

Popular Editions

Ubuntu Desktop
Ubuntu Server

4.Debian

One of the oldest Linux distributions

Known for stability and reliability

Ubuntu is based on Debian

Features

Very stable
Large software repository
Strong security
Community-driven project

Package Manager

Best For

Servers
Stable environments
Advanced Linux users

5.SUSE Linux Enterprise / OpenSUSE

Developed by SUSE
Available in:
- OpenSUSE (community)
- SUSE Linux Enterprise (commercial)

Features

Strong enterprise tools
YaST administration tool
Stable and secure
Good for enterprise workloads

Package Manager

zypper

Best For

Enterprise systems
SAP workloads
Professional administration

6.Arch Linux

Lightweight and highly customizable Linux distribution

Follows rolling release model

Features

Minimal installation
Latest software packages
Highly customizable
Advanced user-focused

Package Manager

pacman

Best For

Advanced Linux users
Developers
Custom Linux setups

Important

Requires manual setup and Linux knowledge.

History of Linux & Unix

Aryan Vaishnani — Mon, 25 May 2026 06:37:00 +0000

Unix

Unix was Created in 1969 at bell labs by ken Thompson, Dennis Ritchie, and others.

It was designed to be simple, multiuser, multitasking and portable across system.

In the 1970s, Unix become popular in universities and research organizations.

Dennies Ritchie developed the c programming language and Unix was rewritten in C, making it portable to many machines.

Different Unix versions later appeared:

BSD (Berkeley Software Distribution)
System V
Solaris
AIX
HP-UX

Important Features of Unix

Multiuser support
Multitasking
Strong security
File-based system design
Powerful command-line shell
Stability and reliability

Linux

Linux was created in 1991 by Linus Torvalds, a student from University of Helsinki.

Linux was inspired by Unix but was built as a free and open-source operating system kernel.

Linus Torvalds released Linux under the GNU Project license, allowing anyone to use, modify, and distribute it.

Linux combined with GNU tools formed complete operating systems called Linux distributions.

Popular Linux Distributions

Ubuntu
Debian
Red Hat Enterprise Linux
CentOS
Fedora
Kali Linux

Important Features of Linux

Open source
Secure and stable
Multiuser and multitasking
Highly customizable
Supports servers, cloud, DevOps, and containers
Widely used in supercomputers and enterprises

Difference Between Unix and Linux

Unix	Linux
Developed in 1969	Developed in 1991
Mostly proprietary	Open source
Used mainly in enterprises	Used everywhere
Expensive commercial versions	Mostly free
Original operating system family	Unix-like operating system

Impact of Unix and Linux

Unix became the foundation of modern operating system design.
Linux powers:
Web servers
Cloud platforms
Android devices
Supercomputers
DevOps infrastructure
Kubernetes and containers
Modern systems like macOS are also Unix-based.