从ubuntu 12.04升级到14.04后无法安装/恢复jenkins

我将Ubuntu从12.04升级到14.04，很惊讶地发现我先前安装和配置的jenkins已损坏。如果我做一个apt-get install jenkins或，那将更加令人痛苦apt-cache search jenkins。我没有看到jenkins或jenkins-cli或jenkins-common。

如果我执行，则会apt-get install jenkins收到错误消息：

buildman@pluto:~$ sudo apt-get install jenkins
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package jenkins is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'jenkins' has no installation candidate

我的操作系统详细信息：

buildman@pluto:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.1 LTS
Release:    14.04
Codename:   trusty

关于如何摆脱混乱（我创建的）的任何指示都将有很大的帮助。