ufw — simple firewall management

💬 "ufw command"

ufw manages iptables with human-readable rules. It sets default policies and allowed ports.

Before making changes, it’s important to check the current rules with status.

• Concept: Manages firewall rules (allow/deny).
• status verbose: Shows current rules and default policies.
• allow/deny: Allows or blocks ports or services.
• Default policy: incoming deny, outgoing allow is typical.

Frequently used options

Three essential command combinations

• ufw status verbose — Check current rules (required before changes)
• ufw allow 443/tcp — Allow the HTTPS port
• ufw limit 22/tcp — Limit SSH connection attempts

💬 "Tell me the order to use when setting up a new server"

Here are common situations on production servers, arranged in order.

Step 1 · Check current rules

Check open ports and policies.

ufw status verbose

Step 2 · Allow only necessary ports

Open only the minimum service ports.

ufw allow 443/tcp

Step 3 · Apply and verify

Check status and actual connectivity.

ufw status | grep 443 && curl -sI https://example.com | head -1

How this is used in practice

1. Open a web port

Situation — A new service needs to be served on 443.

ufw allow 443/tcp && ufw status | grep 443

Result — The rule is added and the service becomes accessible from outside.

Key point — If you haven’t checked the SSH port first, you can lose remote access.

2. Clean up unnecessary ports

Situation — An old port 8080 is open.

ufw status | grep 8080 && ufw delete allow 8080/tcp

Result — The rule is removed, reducing exposure.

Key point — Remove rules only after verifying service impact.

Things to watch out for

• If the default policy is deny immediately after enable, remote access can be lost when there is no SSH rule.
• Because ufw runs on top of iptables/nftables, it can conflict with container networking.
• Rule changes affect production, so they require prior review and approval.

Actual output

This is the result of checking firewall rules and default policies.

!ufw command output: firewall rules

Production server

Source (HTML): https://games.aidebatehub.com/programs/linux/network/ufw.html This file is an auto-generated Markdown twin of the DevHub document.