No record of which repository a package was installed from

[Matthew Paul Thomas]

Currently, for any given package you have installed, there is no record of which source/repository it was installed from.

This is important if, for example, you want to remove an experimental repository (such as a PPA). The repository may no longer contain those packages, and may no longer even exist, but you may still want to remove all software that was installed from that repository (bug 625628).

It may also be helpful, when diagnosing problems, to tell whether any installed packages are from unusual sources.

apt could record the source used whenever installing or upgrading/downgrading a package.

[John Swing (john-swing)]

If I'm not wrong I think the command apt-cache policy <package> show the source it was installed from.

[Dimitri John Ledkov (xnox)]

@ John Swing
If and only if the said package/version still exists in one of your sources. Otherwise it's reported as:
$ apt-cache policy linux-image-3.7.0-5-generic
linux-image-3.7.0-5-generic:
  Installed: 3.7.0-5.13
  Candidate: 3.7.0-5.13
  Version table:
 *** 3.7.0-5.13 0
        100 /var/lib/dpkg/status

Or a slightly more descriptive name in Synaptic is "local or obsolete"

[Daniel Hartwig (wigs)]

> If I'm not wrong I think the command apt-cache policy <package> show
> the source it was installed from.

That command shows the sources each version is /available/ from, not
where it was installed from.

> If and only if the said package/version still exists in one of your sources.

Some times, and only by coincidence. That is not a reliable indicated
of whether such a package was installed from a particular source.