I have found that the Pear 8 mix of software works on a wider range of hardware than anything else, but since it was discontinued at the 13.04 release of Ubuntu updates for it have disappeared. Here is how I managed to upgrade it to the Ubuntu 14.04 tree and keep the Mac-like launcher at the bottom.

First, changes the repository in the main sources.list as well as /etc/apt/sources.list.d, but then disable the added repositories in /etc/apt/sources.list.d until later:

sudo sed -i 's/raring/trusty/g' /etc/apt/sources.list
find /etc/apt/sources.list.d -type f -exec sudo sed -e 's/raring/trusty/g' -i {} \;
for foo in /etc/apt/sources.list.d/*list; do sudo mv -v $foo $foo.disabled; done

Edit the sources.list file and put a hash-mark (#) in front of any pearlinus-repo.fr entries near the top. For example:

sudoedit /etc/apt/sources.list

# deb http://pearlinux-repo.fr/ Rocha main

Then:

sudo apt-get update
sudo apt-get dist-upgrade

You can do those both on one line with two ampersands (&&) between them, but I like to do them separately so I can check out any errors from the first before going on to the second. For example, I have some third-party repositories that do not have “trusty” releases, so I see some messages such as:

W: Failed to fetch http://ppa.launchpad.net/webupd8team/experiments/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found

I can perform the upgrade with these warnings, but it's good to be told what I will be losing in advance so I can think about it before continuing with the dist-upgrade step. The launchpad.net entry can be checked by going to launchpad.net and typing in the project name, in this case “webupd8team”, to see what may have changed.

On a couple of my machines I ended up with this issue:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Failed
The following packages have unmet dependencies.
 python3-apt : Depends: python3 (< 3.4) but 3.4.0-0ubuntu2 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

This is an annoying problem to fix. Here's how I did it:

Now you can remove obsolete software and update the boot loader:

sudo apt-get autoremove
sudo update-grub

On one of my machines a part of apt disappeared, so I did:

apt-get install software-properties-common

Now enable the extra software repositories and update them:

for foo in /etc/apt/sources.list.d/*list; do sudo mv -v $foo $foo.disabled; done

Finally, re-install the docking bar/launcher:

sudo add-apt-repository ppa:ricotz/docky
sudo apt-get update
sudo apt-get install plank