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How to Parse Command-Line Options in Bash with getopts
Parse short options in Bash scripts with getopts: option strings, OPTARG and OPTIND, silent error handling, long-option workarounds, and complete script examples.

How to Find Which Process Is Using a Port in Linux
Find the Linux process listening on a TCP or UDP port with ss, lsof, fuser, or netstat, then inspect and stop it safely.

CIDR Notation and Subnetting Explained
CIDR notation defines IP network size with a prefix length. This guide explains subnet masks, address ranges, host counts, and practical IPv4 subnetting.

SSH Connection Refused: Causes and Fixes
Fix the SSH "Connection refused" error by checking the destination, listening port, OpenSSH service or socket, firewall rules, and port forwarding.

How to Upgrade to Ubuntu 26.04
Upgrade Ubuntu 25.10 or 24.04 LTS to Ubuntu 26.04 Resolute Raccoon, including the early command-line path before the 26.04.1 point release.

How to Connect to a Docker Container
This guide explains how to connect to a running Docker container using docker exec and docker attach, with examples for getting a shell, running commands, and viewing logs.

Dockerfile COPY vs ADD: Which to Use
Compare Dockerfile COPY and ADD for local files, build stages, remote URLs, Git repositories, and tar extraction, with clear guidance on when to use each.

Linux uname Command: Print System Information
The uname command prints kernel name, version, architecture, and hostname. This guide covers all uname options with examples and practical scripting uses.

which Command in Linux: Find Executable Locations
Use the which command to locate executables in PATH, list every match, and check command availability. Compare which with command -v, type, and whereis.

How to Set or Change the Time Zone in Linux
Check and change the Linux system time zone with timedatectl, choose the correct Region/City value, verify /etc/localtime, and handle non-systemd systems.

Series
Cheatsheets
mount Cheatsheet
Quick reference for the mount command: mount and unmount filesystems, mount options, UUID and label mounts, network shares, and /etc/fstab entries
head Cheatsheet
Quick reference for showing the first lines or bytes of files and limiting command output with head in Linux
sha256sum Cheatsheet
Quick reference for generating and verifying SHA-256 and MD5 checksums with sha256sum, md5sum, and related Linux hash commands
Docker Compose Cheatsheet
Docker Compose quick reference: lifecycle commands, Compose file directives, health checks, environment variables, profiles, scaling, and cleanup.




