This post covers the section listed below on the Certified Jenkins Engineer (CJE) exam.
Section #1: Key CI/CD/Jenkins Concepts
- What are fingerprints?
- How do fingerprints work?
What are fingerprints?
Jenkins utilizes fingerprints for tracking a specific instance of a file. This is critically important when attempting to determine which particular version of a file was used during a build. The fingerprint of a file is simply a MD5 checksum that can be used for comparing files.
An example fingerprint (MD5 checksum) is provided below for reference.
How do fingerprints work?
The fingerprints are stored as xml files in the $JENKINS_HOME/fingerprints directory on the Jenkins master. The xml file contains the Jenkins job name, build number, MD5 checksum, and fingerprinted file name.
<?xml version='1.0' encoding='UTF-8'?> <fingerprint> <timestamp>2016-03-15 19:26:54.777 UTC</timestamp> <original> <name>Test</name> <number>1</number> </original> <md5sum>d41d8cd98f00b204e9800998ecf8427e</md5sum> <fileName>testfile.txt</fileName> <usages> <entry> <string>Test</string> <ranges>1</ranges> </entry> </usages> <facets/> </fingerprint>