How to tell from what Ubuntu or Debian repository a package comes?

On a Debian-based system, including Ubuntu, how can one tell which repository a package will be downloaded from, without actually beginning the download? aptitude show and apt-cache info will show the section (e.g., metapackage, base, graphics), but not the repository to which a package belongs (e.g., http://ppa.launchpad.net/mactel-support/ppa/ubuntu or http://us.archive.ubuntu.com/ubuntu/).

When installing the package, the actual repository appears during the download (it is printed out in the "downloading from ..." output from apt and similar programs), but how can one obtain information on the repository containing the package (or a specific version of a package) without downloading and installing it first?

Additionally, how can one determine the source repository for a package that is already installed?

I run apt-cache policy <package name>:

$ apt-cache policy wajig
wajig:
  Installed: 2.1
  Candidate: 2.1
  Version table:
 *** 2.1 0
        100 /var/lib/dpkg/status
     2.0.47 0
        500 file:/home/wena/.repo_bin/ squeeze/main i386 Packages
        500 ftp://ftp.is.co.za/debian/ squeeze/main i386 Packages

That means that there are three wajig packages:

• One that is installed (/var/lib/dpkg/status)

• One that is available from a local repository (file:/home/wena/.repo_bin/)

• One that is available from a remote repository (ftp://ftp.is.co.za/debian), which also happens to have the same version (2.0.47) as the one in a local repository

Additionally, apt-cache madison <package name> will display similar information in a tabular format.

 wajig |        2.2 | mirror://mirrors.ubuntu.com/mirrors.txt/ precise/universe amd64 Packages
 wajig |        2.2 | mirror://mirrors.ubuntu.com/mirrors.txt/ precise/universe Sources

Aha! Apparently, the proper apt command is not apt-cache info, but instead, apt-cache showpkg.

$ apt-cache showpkg linux-generic
Package: linux-generic
Versions: 
2.6.31.19.32 (/var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_karmic-updates_main_binary-amd64_Packages) (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_karmic-security_main_binary-amd64_Packages) (/var/lib/dpkg/status)
 Description Language: 
                 File: /var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_karmic-updates_main_binary-amd64_Packages
                  MD5: 5d722da329763b9342d322f5a140005c

2.6.31.14.27 (/var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_karmic_main_binary-amd64_Packages)
 Description Language: 
                 File: /var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_karmic_main_binary-amd64_Packages
                  MD5: 5d722da329763b9342d322f5a140005c


Reverse Depends: 
Dependencies: 
2.6.31.19.32 - linux-image-generic (5 2.6.31.19.32) 
2.6.31.14.27 - linux-image-generic (5 2.6.31.14.27) 
Provides: 
2.6.31.19.32 - 
2.6.31.14.27 - 
Reverse Provides: 

The File: line provides the repository information after the /var/lib/apt/lists/.

There is a bug report that aptitude cannot display the source repository, but it seems at present the feature is still on the wish list.

I wonder why no one mentioned aptitude. I use it all the time.

Aptitude is:

• Shipped by default with many Debian-based distributions. Can be installed to other (such as Ubuntu) via sudo apt install aptitude.

• Does not require administrative privileges (at least for the command below).

• Does have a nice ncurses GUI (but most of the time used without it).

• Provides a really pretty output. To show versions of packages, use aptitude versions command:

   me@wheezy:~$ aptitude versions kde-standard
   Package kde-standard:                        
   i A 5:77+deb7u1     stable              500
   p A 5:84            testing,unstable    130
  

• Does NOT have Super Cow Powers.

The letter in front of each string indicates the package's status, i is installed and p is purged (or never installed), stable, testing and unstable are repository definitions, the number in the end is a pin priority.

One caveat regarding recent versions of aptitude worth a mentioning here: by default it shows all the packages, which include the name you search, so use a regex magic a little to search by the strict name, for example aptitude versions ^kde-workspace$.

This works for me (shows where the 2vcard package is):

$ grep 2vcard /var/lib/apt/lists/* | grep "Filename:"

/var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_karmic_universe_binary-i386_Packages:Filename: pool/universe/2/2vcard/2vcard_0.5-3_all.deb

You can apply additional filtering to check versions, etc., if multiple versions are available.