How can be found from which repository package has been installed if source was purged from source list

Question

I have several repositories listed in my source list and some ppa added as sources

Can I know from which one specific package has been installed?

It is still possible if after installation repository was removed from source list?

Answer 1

Using apt-cache:

apt-cache policy <your_package_name>

After the removal of the repository, you can't access this information.

---

Example

% apt-cache policy atom
atom:
  Installed: (none)
  Candidate: 1.0.0-1~webupd8~0
  Version table:
     1.0.0-1~webupd8~0 0
        500 http://ppa.launchpad.net/webupd8team/atom/ubuntu/ vivid/main i386 Packages

% sudo rm /etc/apt/sources.list.d/webupd8team-ubuntu-atom-vivid.list
% sudo apt-get update

% apt-cache policy atom                                              
N: Unable to locate package atom