Network - Fully Qualified Domain Name (FQDN)


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: Linux - Fully Qualified Domain Name (FQDN)


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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