Upgrade Varnish on Ubuntu

So you want to switch from the Ubuntu universe package to the 'official' package from varnish-cache.org?

First, follow these instruction to configure the correct repository: https://www.varnish-cache.org/installation/ubuntu

Don't do this:

$ sudo aptitude install -V varnish                        
The following packages will be upgraded: 
  varnish [3.0.2-1ubuntu0.1 -> 3.0.4-1~precise]  
1 packages upgraded, 0 newly installed, 0 to remove and 2 not upgraded.

The problem is you also need to upgrade the shared library:

$ sudo aptitude install -V varnish libvarnishapi1                                                
The following packages will be upgraded: 
  libvarnishapi1 [3.0.2-1ubuntu0.1 -> 3.0.4-1~precise]  varnish [3.0.2-1ubuntu0.1 -> 3.0.4-1~precise]  
2 packages upgraded, 0 newly installed, 0 to remove and 1 not upgraded.