1 wget -q -O - https://jenkins-ci.org/debian/jenkins-ci.org.key | sudo apt-key add -
2 sudo sh -c 'echo deb http://pkg.jenkins-ci.org/debian binary/ > /etc/apt/sources.list.d/jenkins.list'
3 sudo apt-get update
4 sudo apt-get install jenkins

The 4th command failed to setup jenkins successfully.

Refer:
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...
Processing triggers for ureadahead (0.100.0-16) ...
Processing triggers for ca-certificates (20141019ubuntu0.14.04.1) ...
Updating certificates in /etc/ssl/certs... 0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d....
done.
done.
Errors were encountered while processing:
jenkins
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@vagrant-ubuntu-trusty-64:~# echo $?
100