How to Linux

Foundational Linux skills for running a server: the command line, SSH, users and permissions, packages, services, and files.

7 guides in this section.

How to Set Up a Firewall with UFW on Ubuntu and DebianHow to configure the UFW firewall on Ubuntu or Debian: allow SSH and your services, enable the firewall, check its...

Linux Basics

How to Fix an IPv6 dadfailed Address on a Linux ServerFix an IPv6 address marked dadfailed on Linux: find the duplicate MAC in the kernel log, check the server's own...

How to Fix GRUB After a BIOS/UEFI Mismatch on an Ubuntu ServerFix an Ubuntu server that will not boot after a BIOS/UEFI GRUB mismatch: identify the boot mode, chroot from rescue...

How to Upgrade Ubuntu Server to a New Release over SSH SafelyHow to upgrade an Ubuntu server to a new release over SSH with do-release-upgrade: recovery access, backups,...

Initial Server Setup with Ubuntu on a Noiz VPSThe first things to do on a new Noiz VPS running Ubuntu: update the system, create a non-root sudo user, set up SSH...

SSH

How to Set Up SSH Key-Based Authentication on a Linux ServerHow to log in to a Linux server with SSH keys instead of a password: generate a key pair, install the public key on...

Where SSH Keys Are Stored in LinuxWhere SSH keys live on a Linux system: your own keys in ~/.ssh, the server's authorized_keys and known_hosts, the...