Security
Security hardening, SSH protection, firewalling, access control, and auditing tools.
How to Generate a Random Password or String in Linux
Generate random passwords and strings in Linux with openssl rand, /dev/urandom, pwgen, and Python. Choose hex, Base64, URL-safe tokens, or passphrases.
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.
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.
How to List and Delete UFW Firewall Rules
List UFW firewall rules with ufw status and ufw show, then delete them by number or by specification. Covers numbered output, the show reports, rule reset, and SSH lockout recovery.
How to Open a Port in the Firewall on Linux
Open a port in a Linux firewall with ufw, firewalld, nftables, or iptables, then make the rule persistent and test remote access.
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.
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.
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.
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.
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.
