I had installed Jenkins in my Ubuntu 12.04. And i forgot my Jenkins password
kumar@Ubuntu:~$ sudo su -l jenkins
jenkins@Ubuntu:~$ rvm reload
RVM reloaded!
jenkins@rome:~$ rvm install 2.0.0
Searching for binary rubies, this might take some time.
Installing requirements for ubuntu, might require sudo password.
[sudo] password for jenkins:
Sorry, try again.
[sudo] password for jenkins:
Sorry, try again.
[sudo] password for jenkins:
Sorry, try again.
sudo: 3 incorrect password attempts
Please let me know how to recover the password. Thanks
Login as root, do a
if you are not root, ask the administrator of your machine to do this.
BTW: this is not really a jenkins question, I've removed the jenkins tag and added linux.
Update: you might not have a root user with a password on your system, but your kumar user probably has sufficient rights using sudo. (sudo without specifying a user basically means 'do as root')
now you have to pay attention, since the first password you have to type is the password of your kumar user, and only after that the system will ask you for the new jenkins user password.