SSL Certificates Are Expiring Faster: Every Change Through 2029
SSL certificate lifetimes drop to 200, 100 and then 47 days by 2029, and Let's Encrypt moves to 45 days. What changes when, and how to stay ahead.
SSH & Security
SSH tutorials and server security guides: OpenSSH, password and key authentication, MFA, X11 forwarding and SSL certificates.
Avoiding SSL Certificate Problems Before They Break Your Site
Why SSL certificates fail (expiry, revocation, hostname mismatch) and how to monitor them automatically so they never break your site or your users' trust.
How to Recover a Linux Cloud Instance with a Lost or Corrupted SSH Key
Locked out with 'Permission denied (publickey)'? Recover your Linux cloud instance by attaching its boot volume to a temp server and replacing the SSH key.
OpenSSH Step-by-Step Tutorial
Learn to connect to a remote server with OpenSSH: password authentication, key-based login with SSH keys and connecting on a non-default port. Video guide.
Set Up X11 Forwarding for Remote Graphical Applications
Run graphical apps from a remote server over SSH: install an X server (XQuartz, Xming), enable X11Forwarding in sshd_config and connect with ssh -X or -Y.
Configure MFA for SSH with Google Authenticator
Add multi-factor authentication to SSH on Ubuntu with libpam-google-authenticator: set up the app, configure PAM and sshd_config, and require MFA per user.
Enable SSH Password Authentication
Cloud servers disable SSH password login by default. Here's how to enable PasswordAuthentication in sshd_config, restart SSH and log in with a password.