Linux Commands

Command references for core Linux tools, syntax, examples, and practical one-liners.

Setting default file permissions with the Linux umask command

Jul 19, 2026 • 9 min read • series

umask Command in Linux: Set Default File Permissions

The umask command sets the default permission mask for newly created files and directories. This guide explains how umask works, how to calculate its value, and how to make it permanent.

Developer using the export command in a Linux terminal beside the Tux mascot

Jul 19, 2026 • 5 min read • series

export Command in Linux: Set Bash Environment Variables

Use export to turn Bash shell variables into environment variables that child processes inherit, list exported variables, and make them permanent across sessions.

Using the lsof command to list open files and network connections in Linux

Jul 18, 2026 • 8 min read

lsof Command in Linux: Find Open Files and What Is Using a Port

Use the lsof command to find what is using a port, identify processes holding files open, and locate deleted files that still consume disk space.

Jul 17, 2026 • 4 min read

How to Unzip a .gz File in Linux

Unzip a .gz file in Linux with gzip or gunzip, keep the original file when needed, and extract .tar.gz archives with tar.

GZ file icon beside the text unzip .gz file on a yellow background

Jul 16, 2026 • 8 min read

sha256sum and md5sum: Verify Checksums in Linux

Check a file's SHA-256 or MD5 checksum in Linux: generate digests with sha256sum and md5sum, verify SHA256SUMS lists with -c, and confirm ISO downloads.

Verifying file integrity with sha256sum and md5sum in Linux

Jul 16, 2026 • 4 min read • new

What Is stdin, stdout, and stderr in Linux

stdin, stdout, and stderr are Linux's three standard streams. See how file descriptors 0, 1, and 2 connect commands to terminals, files, and pipes.

Diagram of stdin entering a Linux process and stdout and stderr leaving it

Jul 14, 2026 • 5 min read

less Command in Linux: Navigate and Search Files

How to use the less command in Linux to view files page by page, search for text, follow log files in real time, and navigate with vi-style key bindings.

Jul 13, 2026 • 6 min read • series

passwd Command in Linux: Change User Passwords

Change your own, another user's, or the root password in Linux with the passwd command. Covers password expiry with chage, forcing a change at next login, and account locking.

Jul 13, 2026 • 6 min read • new

tree Command in Linux: Display Directory Structure

The tree command lists directories recursively as an indented tree. This guide covers installation, depth limits, filtering, sizes, and saving the output.

Displaying a nested directory structure in a Linux terminal with the tree command

Jul 12, 2026 • 11 min read

curl Command in Linux: Usage and Examples

The curl command transfers data to and from servers using HTTP, HTTPS, FTP, and other protocols. This guide covers downloads, headers, POST requests, verbose debugging, proxies, and API usage.

Using the curl command in Linux to transfer data and query APIs

Jul 11, 2026 • 8 min read

nohup Command in Linux: Background Jobs and Output

nohup keeps commands running after logout. The 'appending output to nohup.out' message is not an error. This guide covers background jobs, 2>&1 redirection, and stopping processes.

Using the nohup command in Linux to run commands after logout

Jul 11, 2026 • 8 min read

tmux Command in Linux: Sessions, Windows, and Panes

The tmux command lets you run persistent terminal sessions with multiple windows and panes. This guide covers creating and managing sessions, splitting panes, copy mode, and configuration.

Using tmux to manage terminal sessions, windows, and panes in Linux

Jul 11, 2026 • 5 min read

strace Command in Linux: Trace System Calls

Use the strace command to trace system calls and signals on Linux, debug why a program fails, find missing files, and measure where a process spends its time.

Tracing system calls with the strace command in Linux

Jul 10, 2026 • 7 min read

How to Manage Node.js Processes with PM2

How to install PM2, run and manage Node.js processes with clustering, zero-downtime reloads, log rotation, and systemd integration that survives reboots.

Jul 8, 2026 • 11 min read

htop Command in Linux: How to Monitor and Manage Processes

Monitor Linux processes in real time with htop: read CPU and memory meters, sort and filter the process list, and kill or renice processes from one screen.

Using the htop command to monitor processes interactively in Linux

Jul 8, 2026 • 7 min read

smartctl Command in Linux: Check Disk Health with SMART

Use smartctl in Linux to check SMART health, read disk attributes, run self-tests, troubleshoot USB enclosures, and monitor NVMe wear.

Checking disk SMART health with smartctl in a Linux terminal

Jul 8, 2026 • 10 min read

find Command in Linux: Search Files and Directories

The find command searches for files and directories by name, type, size, date, permissions, and more. This guide covers practical examples including wildcards, exec actions, and combining find with grep.

Using the find command to search for files and directories in Linux

Jul 6, 2026 • 5 min read

How to Create a Directory in Linux: mkdir Command Examples

Create single, multiple, and nested directories in Linux with mkdir, set permissions with -m, and fix 'Permission denied' and 'No such file or directory' errors.

Creating directories in Linux with the mkdir command

Jul 5, 2026 • 9 min read

ffmpeg Command in Linux: Convert, Compress, and Extract Media

Practical ffmpeg examples for converting between formats, compressing video with CRF, extracting audio, trimming clips, resizing video, and batch processing files on Linux.

Converting and compressing video files in a Linux terminal with the ffmpeg command

Jul 2, 2026 • 6 min read

du Command in Linux: Check Disk Usage

The du command reports disk space used by files and directories. This guide covers human-readable output, summary totals, depth limiting, sorting by size, and practical examples.