Network - Fully Qualified Domain Name (FQDN)

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FQDN stands for fully qualified domain name.

It's a name that is said to be absolute (ie that includes the local domain and ends with a dot).

This name identifies uniquely a node in the namespace.

It's also known as:

  • the complete name.
  • absolute name
  • or canonical name

See the absolute name section on the name page to known more about relative and absolute name.


poneria.ISI.EDU. is a fully qualified name whereas poneria is a relative name.


The FQDN is needed to define the URLs. This is the value that you would got in the CN of a web server certificate.

keytool -list -v -storetype jks -keystore truststore.jks -storepass changeit
Alias name: alis_name
Creation date: 26-Sep-2019
Entry type: PrivateKeyEntry
Certificate chain length: 1
Owner:, OU=Gerardnico, O=Gerardnico, L=Oegstgeest, ST=Netherlands, C=NL
Issuer:, OU=Gerardnico, O=Gerardnico, L=Oegstgeest, ST=Netherlands, C=NL
Serial number: 54065f1a
Valid from: Thu Sep 26 05:02:02 UTC 2019 until: Fri Sep 25 05:02:02 UTC 2020



The FQDN is:

  • defined locally in the Host file as the first name after the IP,
  • created by the DNS service when a DNS record is added

On Linux

This article will show you how to manage the FQDN on Linux: How to see and update the Fully Qualified Domain Name (FQDN) on Linux


If your full qualified domain name is too long, you can create fixed length unique identifier with the version 3 and 5 of UUID and the fqdn namespace.

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