Dns

A quick bash one-liner to pull offending IP addresses from exim relay-denied entries and resolve them to hostnames, making it easier to identify which gateways are misconfigured.

A quick workflow for triggering a DNS zone reload with rndc and confirming the result in the system log. Covers the two commands you need and what to look for in the output.

Learn how to configure BIND9 views to serve different DNS records to internal and external clients from a single server. This guide walks through zone files, ACLs, recursion control, and the $include directive to keep your setup clean and secure.

A valid PTR record must resolve to a name that resolves back to the original address. Multiple PTR records for a single address break name resolution and can cause Kerberos ticket verification to fail.

A quick troubleshooting guide for the ‘Server not found in Kerberos database’ error, covering the four most common root causes and how to verify each one.

Inconsistent forward and reverse DNS lookups can cause a cascade of cluster and security issues. This guide walks through quick Python and Java one-liners to verify that your hostname, IP, and reverse record all line up.