4.1.3 Networking & firewalls
Every entry filed under Networking & firewalls and its subtopics.
Level
- Beginner 5
- Intermediate 5
- Advanced 0
What kind of help
- Guided project 2
- Explains an idea 0
- Step by step 5
- Cheat sheet 1
- Fixes an error 2
Works on
- Linux 11 (selected, select to remove)
- macOS 2
- Windows 0
- Browser 0
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
11 entries match these filters
- 0344 ufw and firewalld: open and close ports Allow and remove ports and services on the two standard Linux host firewalls, restrict a port to one source network, and make… Beginner · Step by step · Linux Article Firewalls · Networking & firewalls 15 Oct 2026
- 0349 Set up a WireGuard VPN with wg-easy in Docker Run a WireGuard server with a web admin page on one Linux host, open the UDP port, add a client from the… Intermediate · Guided project · Linux Article Networking & firewalls · VPN & tunnels 15 Oct 2026
- 0320 Fix: address already in use (EADDRINUSE) Something is already listening on the port your program wants. Find the process with lsof or ss, stop it or pick another… Beginner · Fixes an error · Linux, macOS Article Networking & firewalls · Node.js · Processes & ports 15 Oct 2026
- 0342 Which process is using a port, and how to free it Find the program behind a busy port with ss, lsof or fuser, decide whether to stop it properly or kill it, and… Beginner · Step by step · Linux, macOS Article DNS, IP addresses & ports · Networking & firewalls 15 Oct 2026
- 0249 Set up and harden a fresh Linux server in one afternoon Take a new Ubuntu, Debian or Rocky/Alma server from first login to a safer baseline: sudo admin, SSH keys only, firewall, automatic… Beginner · Guided project · Linux Article Networking & firewalls · Packages & updates · Users, sudo & hardening 15 Oct 2026
- 0173 Set a static IP address: nmcli on RHEL vs netplan on Ubuntu RHEL, Rocky and AlmaLinux configure networking with NetworkManager (nmcli); Ubuntu Server uses netplan YAML. Here is the same static IP setup in… Intermediate · Step by step · Linux Article Networking & firewalls 15 Oct 2026
- 0174 Network and DNS troubleshooting commands: ip, ss, dig, resolvectl A layer-by-layer cheat sheet for "the server cannot reach X": interfaces and routes with ip, listening ports with ss, and name resolution… Beginner · Cheat sheet · Linux Article Networking & firewalls 15 Oct 2026
- 0175 Open ports with firewalld and ufw firewalld (RHEL, Rocky, AlmaLinux) and ufw (Ubuntu) are friendly front ends to the kernel firewall. Allow SSH first, then open only the… Intermediate · Step by step · Linux Article Networking & firewalls 15 Oct 2026
- 0180 firewalld: zone-based firewall daemon Upstream source of firewalld, the default firewall manager on RHEL, Rocky Linux, AlmaLinux and Fedora, including firewall-cmd and its service definitions. Linux Repo Networking & firewalls 15 Oct 2026
- 0167 Fix: Job for nginx.service failed because the control process exited with error code systemctl prints this when a service's start command exits with an error. The real reason is in journalctl; for nginx it is… Intermediate · Fixes an error · Linux Article Networking & firewalls · Services & systemd 15 Oct 2026
- 0103 Proxmox VE networking: Linux bridges (vmbr0) and VLANs Guests reach the network through Linux bridges such as vmbr0, defined in /etc/network/interfaces. Learn the default setup, VLAN-aware bridges, VLAN tags for… Intermediate · Step by step · Linux Article Installation & first steps · Networking & firewalls 15 Oct 2026