Practical Linux Tutorials and Command-Line Guides

Search hundreds of step-by-step tutorials for Bash, Ubuntu, networking, security, and more.

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May 9, 2026 • 6 min read

SSH Permission Denied (publickey): Causes and Fixes

How to troubleshoot the SSH "Permission denied (publickey)" error in Linux. Covers file permissions, missing keys, SELinux, SSH agent issues, and server-side debugging.

Use SCP Command to Securely Transfer Files

Apr 24, 2026 • 7 min read

scp Command in Linux: Secure File Transfer Examples

SCP copies files securely between local and remote hosts over SSH. This guide covers syntax, common options, and practical examples for everyday file transfers.

Aug 4, 2026 • 7 min read

Linux Folder Size: How to Check File and Directory Sizes

Check folder and file sizes in Linux with du. Compare directory totals, rank subdirectories, exclude paths, and check free space with df.

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Aug 22, 2026 • 6 min read

How to Change the Hostname in Linux

Change the hostname in Linux with hostnamectl and /etc/hosts. Covers permanent, temporary, cloud-init, and non-systemd methods.

Three illustrated server towers beside the text Change Hostname in Linux

Aug 22, 2026 • 7 min read

curl POST Request Examples

Send data with curl -d, --json, and -F: POST examples for HTML forms, JSON APIs, file uploads, and reading the body from a file or stdin.

Aug 22, 2026 • 12 min read • series

Sudo Command in Linux: Run Commands as Root

The sudo command runs programs as root or another user. This guide covers sudoers setup, root shells, sudoedit, credential caching, and common sudo options.

Linux sudo command running a command as root in a terminal

Aug 21, 2026 • 6 min read • series

How to Generate SSH Keys on Linux with ssh-keygen

Generate an SSH key pair on Linux with ssh-keygen, choose between Ed25519 and RSA, and install the public key on a server, a Git host, or a cloud provider.

Aug 21, 2026 • 9 min read • new

DNS Record Types Explained: A, AAAA, CNAME, MX, TXT, and More

DNS record types map domains to servers, route email, publish verification data, and control certificate issuance. See zone-file examples and dig queries.

DNS record cards linking a domain to IP addresses, mail servers, and security policies

Aug 21, 2026 • 12 min read

How to Extract tar.xz Files in Linux

Extract .tar.xz and .txz archives in Linux with tar. Covers extracting to a directory, listing contents, decompressing plain .xz files with unxz, and installing software from a tar.xz download.

Aug 21, 2026 • 6 min read

Initial Server Setup on Ubuntu 26.04

Prepare a new Ubuntu 26.04 server with a sudo user, SSH key authentication, UFW firewall rules, a hostname, timezone settings, and system updates.

Aug 21, 2026 • 16 min read

Linux cp Command: Copy Files and Directories

The cp command copies files and directories in Linux. This guide covers recursive and archive copies, copying directory contents, overwrite control, and attributes.

Using the Linux cp command to copy files and directories

Aug 21, 2026 • 9 min read • series

How to Set Up Passwordless SSH Login

Set up passwordless SSH login with Ed25519 or RSA key pairs. Copy public keys with ssh-copy-id, use the ssh-agent, and disable password authentication for hardened access.

Aug 20, 2026 • 13 min read

How to Use sed to Find and Replace Strings in Files

Replace strings in files with sed: run sed -i 's/old/new/g' file. Covers global, case-insensitive, word-boundary, regex, line-range, and recursive replace.