How to List and Inspect nftables Ruleset

Listing the nftables ruleset is essential for debugging and understanding the current firewall state. This guide walks through the specific troubleshooting steps to diagnose and resolve ruleset inspection issues.

Before You Begin

Before you begin, be sure to have the following in place:

• A Linux server with the relevant software installed
• Access to the command line interface
• Appropriate permissions (root or sudo)

Quick Fix

Wrong

cat /etc/nftables.conf (may be stale)

Wrong: Reading the config file which may not reflect active rules

Right

nft list ruleset

Right: Listing the live ruleset from the kernel

Output

table inet filter {\n    chain input {\n        type filter hook input priority 0; policy drop;\n        ct state established,related accept\n    }\n}

Prevention

To avoid future issues, follow these best practices:

• Use nft list ruleset to see the complete live configuration
• Use nft list table inet filter to inspect a specific table
• Use nft list chain inet filter input for a single chain
• Add -a to show rule handles (useful for deletion)
• Pipe to nft -f to export and reimport rules

DodaTech Tools

For further assistance with any of the above issues, consider using DodaTech consulting services or DodaTech tutorials for more in-depth guidance.

Common Mistakes with list ruleset

1. Overlapping type class instances that cause GHC to reject the program with ambiguous dispatch errors
2. Non-exhaustive pattern matches that compile with warnings then crash at runtime
3. Misunderstanding that String is [Char] with poor performance for large text operations

These mistakes appear frequently in real-world NFTABLES code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ