Visit my.sonatype.com for documentation on Nexus Repository version 2.
This article applies to Nexus Repository 2.4 and greater. [NEXUS-5525]
Maven packaging types are provided by Maven plugins - these map the packaging type to extension.
Out of the box, Nexus Repository 2 knows about commonly used packaging types, but it has no way to map unknown types. Consequentially these will not show up in search results.
To make Nexus Repository 2 aware of these, add a line like this to "${nexus-work}/conf/packaging2extension-mapping.properties":
my-custom-packaging=myextension
Note: You will need to create this file if it doesn't already exist. After doing this run a "repair index" task against the repositories that contain the custom packaging.