Linux on Documentation

Linux: Fundamentals of Swap Space

Wed, 08 Jul 2026 13:21:43 +0530

Linux swap memory is a portion of disk storage used as virtual memory to supplement RAM, allowing the system to continue running when physical memory is full.

Linux: Booting Process

Fri, 25 Jul 2025 19:33:51 +0530

High-level explanation of how the Linux is booted.

Package Management

Mon, 21 Jul 2025 19:48:46 +0530

Essential package management and real world examples that cover all fundamental operations for managing RPM/DEB packages.

What is LVM (Logical Volume Manager) and Why Use it?

Sun, 20 Jul 2025 19:35:31 +0530

What is LVM?

LVM is a special tool in Linux that let’s you manage disk storage in much more flexible way than traditional partitions.

Think of it as turning multiple hard drives into a big, flexible stroage pool that you can split, resize, or grow whenever you want, without worrying about the limits of classic disk partitions.

Why Use LVM?

Resize storage easily: You can expand or shrink volumes without reformatting or losing data.
Combine multiple disks: Make many drives look like one big storage area.
Add more space anytime: Plug in new hard drive and add its space instantly.
Move or migrate data: Shift storage between drives with little downtime.
Take snapshots: Save the exact state of you data at a moment in time, which helps with backups.

Practical Example

Classic Partitioning (without LVM)

You have 100GB disk with /home and /var partitions.
/home fills up, while /var has lots of free space.
Problem: You can’t take space from /var and give it to /home without migrating, deleting, repartitioning or copying data aroud. Which is possible but risky and time-consuming.

With LVM

Let’s say you have two physical disks:

Linux Environment Variables

Fri, 18 Jul 2025 23:36:37 +0530

Environment Variables

In Linux, Environment variables are named key-value pairs that store information about your operating environment and configuration. They are crucial because they let the operating system, applications, and scripts know about elements such as :

Where programs are location; _via _PATH.
Your user/currently logged-in directory; HOME.
Language or locale settings.
System-wide or app-specific configurations.

In simple terms, environment variables are a foundational way that Linux customizes, configues, and manages the actions of programs and users through simple “key=value” pairs.

Linux Messaging Basics: mail, wall & write

Fri, 18 Jul 2025 00:00:52 +0530

Use mail to send or receive stored messages & system notificaitons, wall to broadcast announcements to all users and use write for quick direct messages to another user.

Fundamentals of Regular Expressions

Sun, 13 Jul 2025 19:51:31 +0530

Regular Expression

Regular expression is a method of pattern matching. It allows you to define patterns of texts and search for it in other texts, no matter the complexity or the amount of text there is to process.

Using regular expression is considered a more efficient solution, when there’s complexity in searching for a text that you want to find. It is also called as regex.

Keep in mind that regular expression is supported in almost every programming language. If you were to face a situation when there’s complexity in searching a text, take a look at how the systax looks like other programming languages and utilize them.

Packaging: Debian File Deep Dive

Sat, 05 Jul 2025 22:29:13 +0530

Detailed explanation of Debian packaging file structure.

Packaging: RPM Spec File Deep Dive

Sat, 05 Jul 2025 12:39:02 +0530

Detailed explanation of RPM package file structure.

Linux Tools: Getting Started with the tar Command

Sat, 05 Jul 2025 10:13:55 +0530

The tar command (short for tape archive) is a foundational tool in Linux for archiving and compressing files and directories

Linux Tools: Basic File Viewing & Handling

Fri, 04 Jul 2025 21:40:45 +0530

Read and preview file contents using commands like cat, head, tail, less.

Linux Tools: Data Extraction & Manipulation

Fri, 04 Jul 2025 20:42:38 +0530

Focuses on shaping, refining, or deduplicating data using cut, sort, uniq commands.

Packaging: Build Your First Debian Package!

Fri, 04 Jul 2025 00:10:18 +0530

Create a simple “Hello World” C program, prepare necessary Debian packaging files (debian/) build the .deb pacakge, install it to test and remvoe it.

Packaging: Build Your First RPM Package!

Thu, 03 Jul 2025 14:13:41 +0530

Create a simple “Hello World” C program, write a .spec file, build an RPM package with rpmbuild, install it to test, and then remove it.

Linux Tools: Transform & Edit

Mon, 30 Jun 2025 16:00:03 +0530

Modify or reformat text streams or files; Command: awk & sed

Linux Tools: Search & Filter

Mon, 30 Jun 2025 15:20:08 +0530

Searches for patterns in text (files or streams) using regular expressions and Searches for files and directories based on name, size, date, permissions, etc.

Linux: Advanced Filtering and Analyzing System Logs with journalctl

Mon, 30 Jun 2025 10:38:19 +0530

What is `journalctl` Filters?

You can use filters with journalctl to narrow down and control which log entries are displayed. journalctl supports a wide range of filtering options, both by structured fields and by command-line flags.

Structured Fields: SYSLOG_IDENTIFIER, _SYSTEMD_UNIT, _UID, etc
Command-Line Fields: --since, --until, -u, -p, --grep, etc

Common `journalctl` Filters

Filter Type	Example Command	Description
By Time	`journalctl --since "8 hours ago"`	Shows logs since a specific time
By Service/Unit	`journalctl -u nginx.server`	Show logs for a specific server/unit
By Priority	`journalctl -p warning`	Show logs at/above a certain severity
By Field	`journalctl SYSLOG_IDENTIFIER=sudo`	Show logs where a field matches a value
By Boot	`journalctl -b -1`	Shows logs from the previous boot
By Keyword	`journalctl --grep "error"`	Shows logs containing a keyword

Advanced `journalctl` Filters

Filter Type	Example Command	Description
By User ID	`journalctl _UID=user_id`	Filter logs by the user ID of the process that generated them
By Group ID	`journalctl _GID=group_id`	Filter logs by the group ID of the process that generated them
By Process ID	`journalctl _PID=process_id`	Filter logs by process ID
By Process name	`journalctl _COMM=nginx`	Filter by process name (eg. `_COMM=nginx`)
By Hostname	`journalctl _HOSTNAME=hostname`	Filter logs by hostname
By Executable Path	`journalctl _EXE=exe_path`	Filter logs by executable path (eg: `/usr/local/bin/hugo`)
By Boot Session	`journalctl _BOOT_ID=boot_id`	Filter logs by a specific boot session
By Audit Session	`journalctl _AUDIT_SESSION=session_id`	Filter logs by audit session ID
By Syslog Facility Code	`journalctl _SYSLOG_FACILITY=facility_number`	Filter by syslog facility code

Alternatively, you can find the available filters in journalctl by using:

Linux: Service Management with systemd

Sun, 29 Jun 2025 20:02:46 +0530

Checking Service Status In Detail

The systemctl status command provides detailed information about a service, including it’s current state (active, inactive, failed), recent log entries, and reasons for failure if the service is not running.

Example Command:

sudo systemctl status apache2
#or httpd service
sudo systemctl status httpd

Output:

iamyaash@pi5:~ $ sudo systemctl status firewalld.service
● firewalld.service - firewalld - dynamic firewall daemon
 Loaded: loaded (/lib/systemd/system/firewalld.service; enabled; preset: enabled)
 Active: active (running) since Sun 2025-06-29 20:30:48 IST; 1s ago
 Docs: man:firewalld(1)
 Main PID: 7956 (firewalld)
 Tasks: 2 (limit: 9585)
 CPU: 279ms
 CGroup: /system.slice/firewalld.service
 └─7956 /usr/bin/python3 /usr/sbin/firewalld --nofork --nopid

Jun 29 20:30:48 pi5 systemd[1]: Starting firewalld.service - firewalld - dynamic firewall daemon...
Jun 29 20:30:48 pi5 systemd[1]: Started firewalld.service - firewalld - dynamic firewall daemon.

The output includes:

Linux: Task Scheduling with systemd Timers

Sun, 29 Jun 2025 16:17:54 +0530

Practical guide to systemd timers, covering the differences from cron, the structure of timer files, key directives, and hands-on exercises.

Linux: Creating and Customizing systemd Units

Sun, 29 Jun 2025 12:15:36 +0530

Important directives: ExecStart, ExecStop, Restart policies; Dependencies and ordering: Requires, Wants, Before, After; Writing your own service units with examples; Overriding units using drop-in configurations (systemctl edit)

Linux: Manage File Permissions

Fri, 27 Jun 2025 20:16:49 +0530

This guide explains how to use Linux commands to manage file permissions, ownership and special permissions. Commands: chmod, chown, and chgrp.

Linux: How To Mount And Un-Mount Permanently/Temporarily

Thu, 26 Jun 2025 20:37:51 +0530

Know how to mount and unmount storage effectively for temporary and permanent storage.

Linux: Assigning Permissions and Group Ownership Automatically For Newly Created Files & Directories (umask & chgrp)

Wed, 25 Jun 2025 11:27:37 +0530

To ensure that new files created in a shared directory are automatically assigned to the directory’s group rather than the group of the user who created them.

Linux: firewalld & iptables

Tue, 24 Jun 2025 22:07:49 +0530

Firewalls in Linux system administration, focussing on both firewalld and iptables.

Linux Tools: dd Utility Tool

Sun, 22 Jun 2025 22:09:10 +0530

dd is a Linux tool, and it widely used for Linux system administration and is essential for many low-level tasks involving disks, partitions, and files at the block level.

Linux: Log Analysis and Journals

Sun, 22 Jun 2025 14:15:38 +0530

Understanding Linux log locations, using journalctl, analyzing traditional logs, filtering and searching logs with grep, less and time filters.

Linux: Networking Tools

Sun, 22 Jun 2025 11:22:47 +0530

Linux networking tools for system administration: ip, ss, netstat, ping, and more.

Linux: Systemd And Service Management

Sat, 21 Jun 2025 14:50:43 +0530

What is systemd and how it works? What are units, services, targets in systemd? Essential commands like systemctl & journalctl, and creating & managing custom services.

Linux: File Systems And Storage

Wed, 18 Jun 2025 16:12:05 +0530

How to manage file systems and storage in Linux operating systems.

Linux: Fundamentals Of File Permissions And Ownership

Tue, 17 Jun 2025 22:07:53 +0530

How to manage file permissions and ownership in Linux based operating systems.

Linux: User & Group Management

Sun, 15 Jun 2025 14:51:16 +0530

How to manage users & groups on Linux based operating systems, with exercise based explanations!

Linux: Directories

Sun, 30 Mar 2025 19:41:36 +0530

A table summarizing Linux directories for a quick reference.