Jenkins's home directory - jenkins

Question

My Jenkins is installed on the default location: /var/lib/jenkins. Every time it builds, it changes my root directory of my workspace (on my local machine /home/john/p4) to /var/lib/jenkins/..., which shouldn't happen?
How to specify my root directory of my client(workspace) so that the build won't change its location? Should I change $JENKINS_HOME? If I should change it, then that's equavilent to the fact that I have to re-install Jenkins to the location I want, because $JENKINS_HOME is supposed to be the root directory for all jenkins files and builds.
What should be the correct behavior of Jenkins and P4 client? Also, does it have anything to do with the user who starts the builds in Jenkins? Does Jenkins user have anything to do with the Linux user who installs Jenkins?

Answer 1

The p4-plugin Jenkins requires it's own Perforce workspace and it WILL set the Perforce workspace root to match the Jenkins workspace root.
Let Jenkins create a new Perforce workspace (use a name that does not exist, I generally prefix it with jenkins-). If you want to be dynamic use a name like:
jenkins-${NODE_NAME}-${JOB_NAME}
...as ${NODE_NAME} and ${JOB_NAME} will expand.
Next define a view mapping (or streams path) to specify the location of the files in Perforce and how you want them to appear in the workspace. e.g.:
View:
//depot/myProj/main/... //jenkins-${NODE_NAME}-${JOB_NAME}/...
As for the user that connects to Perforce, that is defined in the Perforce Credentials, but the files sync'ed to the Jenkins Master (or Slave if you have a build farm) will use the UID/GID of the Jenkins service.
You can find the documentation for the p4-plugin here.