Security
Security hardening, SSH protection, firewalling, access control, and auditing tools.
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.
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.
How to Create a Self-Signed SSL Certificate with OpenSSL
Generate a self-signed SSL/TLS certificate and private key on Linux using the openssl command. Covers RSA and ECDSA keys, Subject Alternative Names (SAN), and non-interactive generation.
su Command in Linux: How to Switch Users
Use the su command to switch users, open a root login shell, and run commands as another account. Includes options, sudo su, troubleshooting, and examples.
chmod 777: What It Means and Why You Should Never Use It
chmod 777 grants every user full control of a file or directory. See why it is risky and when to use safer 755 or 644 permissions instead.
SSH Tunnel: Local, Remote, and Dynamic Port Forwarding
Set up SSH tunnels with the -L, -R, and -D options for local, remote, and dynamic port forwarding, with working examples for Linux, macOS, and Windows.
How to Enable and Disable Root User Account in Ubuntu
This guide explains how to enable and disable the root user account in Ubuntu using the passwd command, and covers safer alternatives like sudo -i and su -.
How to Change User Password in Ubuntu
Change a user password in Ubuntu from the command line with passwd, or through the GNOME Settings app. Covers your own account and other users.
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.
How to Encrypt and Decrypt Files with GPG
Encrypt files with GPG using a passphrase or a key pair, share encrypted files with other people, protect whole directories, and decrypt safely in scripts.
How to Change Root Password in Ubuntu Linux
Set or change the root password on Ubuntu using sudo passwd, switch to the root account, and understand why root login is disabled by default.
What Is an SSL/TLS Certificate and How Does It Work?
An SSL/TLS certificate proves a website's identity and encrypts traffic between the browser and the server. This guide explains how certificates work, what they contain, and the types available.
How to Use OpenSSL: Generate Keys, Certificates, and Test TLS
Practical OpenSSL guide for Linux: generate private keys, create CSRs and self-signed certificates, convert formats, inspect certificates, and test TLS connections.
SSH SOCKS Proxy: Create a SOCKS5 Tunnel for Browsing
Create an SSH SOCKS proxy with a SOCKS5 tunnel, configure Firefox or Chrome to use it, proxy DNS requests, and verify the browser exits through your SSH server.
SSH Hardening Guide: Best Practices for Linux Servers
SSH hardening best practices for Linux servers, including sshd_config checks, key-only logins, root login restrictions, firewall rules, timeouts, and Fail2Ban.
How to Change the SSH Port in Linux
Change the default SSH port 22 by editing sshd_config, adjusting the firewall, and reloading the SSH service on Linux.
ufw Command in Linux: Uncomplicated Firewall Reference
Reference for the ufw command on Linux, with examples for enabling the firewall, allowing and denying traffic, deleting rules, and managing application profiles.
