.JRN File

The jrn file extension is generally used for journal files probably used by Journaling file systems supported by Linux, OS/2 and others.

Journaling file system keeps track of the changes that will be made in a journal (usually a circular log in a dedicated area of the file system) before committing them to the main file system.

How to open:

It does not seem to be possible to open *.jrn files directly.

How to convert:

You cannot convert *.jrn files to anything else.