feat: dig examples

knowledge base/dig.md

@@ -1,7 +1,40 @@
 # Dig
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
+## TL;DR
+
+```sh
+# Installation.
+apt-get install 'dnsutils'
+yum install 'bind-utils'
+
+# Perform a DNS lookup.
+dig 'google.com'
+dig 'google.com' 'A'
+
+# Perform a reverse lookup.
+dig -x '172.217.14.238'
+
+# Only show the IP from the result.
+dig 'google.com' '+short'
+
+# See resolution trace.
+dig 'google.com' '+trace'
+
+# Ask a specific DNS server.
+dig '@8.8.8.8' 'google.com'
+
+# Return all results.
+dig 'google.com' 'ANY'
+```
+
 ## Sources
 
+- [How to Use Linux dig Command (DNS Lookup)]
 - [Using dig +trace to Understand DNS Resolution from Start to Finish]
 
 <!--
@@ -9,4 +42,5 @@
   -->
 
 <!-- Others -->
+[how to use linux dig command (dns lookup)]: https://phoenixnap.com/kb/linux-dig-command-examples
 [using dig +trace to understand dns resolution from start to finish]: https://ns1.com/blog/using-dig-trace