You can not add Launchpad itself as a source but you can add specfic PPA's sources for packages.
For instance the Launchpad Project Old and New Python Versions has a PPA settings block where it details the information needed to add that PPA to your software sources
By doing so, the packages listed on this page will be made available to you.
If you can figure out what DEB goes first here is a list of all the DEBs you need for python 2.5: packages Open the 'python2.5 - 2.5.5-8~ppa2~natty3' and you get to see all the DEBs involved!
You don't need a PPA for that, the package you are mentioning is part of the official Ubuntu repositories, more precisely the universe
repository for Xenial.
This can be verified using the command apt policy libguestfs-tools
, which should directly display you that package from the xenial/universe
repo as installation candidate.
Installing it then is as simple as
sudo apt install libguestfs-tools
You know that a package on Launchpad is part of the official Ubuntu repositories if the author (see the big headline right at the top of the page, with the icon) is "Ubuntu" and not any Launchpad user name. The URL starts with /ubuntu
as well for packages from the official repos.
As you specified an older version in your link, which got updated and is no longer existing in the official repositories, you have no real way of still getting that old version from any repository or PPA.
The Ubuntu repos do not keep old replaced versions of packages around and there also is no Launchpad PPA where they get automatically available. You can download the package directly from the link given on that site, but there will be no real PPA where you get that old version from unless any user manually creates it and rebuilds that old version there themselves.
Best Answer
Just simply run:
it's a supported package which already exist in official repository, and the link you provide is the source of it.
The fact is that you already have access to the source of this package, if you want to download the source you can run:
And if you want to compile and install it from source code:
first install the built dependencies.
then use this command to fetch and compile nwchem
then install it:
or you can use things like gdebi to handle dependencies too.