On Debian-based distributions, such as Ubuntu, you can install Jenkins through apt-get.

Recent versions are available in an apt repository. Older but stable LTS versions are in this apt repository.

You need to have a JDK and JRE installed. openjdk-7-jre and openjdk-7-jdk are suggested. As of 2011-08 gcj is known to be problematic - see https://issues.jenkins-ci.org/browse/JENKINS-743.

Please make sure to back up any current Hudson or Jenkins files you may have.

Installation

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

Upgrade

Once installed like this, you can update to the later version of Jenkins (when it comes out) by running the following commands:

sudo apt-get update
sudo apt-get install jenkins

(aptitude or apt-get doesn't make any difference.)

What does this package do?

If your /etc/init.d/jenkins file fails to start jenkins, on line 108 you may change su -l <username> -c <command> with sudo -u <username> <command>. This fixed init.d script for me (icarito, July 2013).

Deploying on Ubuntu in a cloud (EC2, HP Cloud, OpenStack)

The Ubuntu Jenkins maintainer also maintains the Juju charm deployment/management script for deployment in clouds. It's designed to make it easy to deploy a master with multiple slaves:

juju deploy jenkins
juju deploy -n 5 jenkins-slave
juju add-relation jenkins jenkins-slave

The default password for the 'admin' account will be auto-generated. You can set it using:

juju set jenkins password=mypassword

Always change it this way - this account is used by the charm to manage slave configuration. Then feel free to expose your jenkins master:

juju expose jenkins

Setting up an Apache Proxy for port 80 -> 8080

do not do this next command if you already have virtual hosting setup that depends on the default site. See my comment below - danapsimer

<VirtualHost *:80>
	ServerAdmin webmaster@localhost
	ServerName ci.company.com
	ServerAlias ci
	ProxyRequests Off
	<Proxy *>
		Order deny,allow
		Allow from all
	</Proxy>
	ProxyPreserveHost on
	ProxyPass / http://localhost:8080/ nocanon
	AllowEncodedSlashes NoDecode
</VirtualHost>

Setting up an Nginx Proxy for port 80 -> 8080

This configuration will setup Nginx to proxy port 80 to 8080 so that you can keep Jenkins on 8080. Instructions originally found in a GitHub Gist from rdegges: https://gist.github.com/913102

Where to go from here?