Can I see why a package is installed?

Question

For a specific package, can I find out why it is installed?

So, can I see or it's manually installed, or that it is installed as a dependency of another package? Or that it is installed as part of the distro?

Answer 1

A quick solution is:

aptitude why $package

With the following command

apt-cache rdepends $package

you can see what are the other packages that depend directly on this package, and this can help in understand. You can add the --recurse option, to list all packages that depends directly or indirectly on this package.

Answer 2

Yes, you can, and it's a pretty obvious command, in fact. Assuming you've aptitude installed, you can open up a Terminal Window ad type:

aptitude why package

That should give a list of packages that depend on that specific package. If it's a manually installed package, it will say something like "It wasn't possible to find a reason to install package".

Answer 3

You can also use plain old dpkg.

For example, "dpkg -p zip" provides the following information:

dpkg -p zip
Package: zip
Priority: optional
Section: utils
Installed-Size: 616
Maintainer: Ubuntu Developers
Architecture: i386
Version: 3.0-2
Replaces: zip-crypt (<= 2.30-2)
Depends: libbz2-1.0, libc6 (>= 2.7)
Recommends: unzip
Conflicts: zip-crypt (<= 2.30-2)
Size: 318238
Description: Archiver for .zip files
This is InfoZIP's zip program. It produces files that are fully
compatible with the popular PKZIP program; however, the command line
options are not identical. In other words, the end result is the same,
but the methods differ. :-)
.
This version supports encryption.
Original-Maintainer: Santiago Vila

R.

Answer 4

Here's a simple way that doesn't rely on aptitude, which 10.10 doesn't ship by default anymore.

Notice

You do need root access to run these commands.

Graphically

Open Synaptic and try to remove it.

If a dialog pops up asking you to delete other packages, those are the packages that (recursively) depend upon it.

From terminal

apt-get remove package_name_goes_here -s

Again, the packages that would be removed as a result are all those that (recursively) depend on it. (The -s parameter tells apt-get to not actually remove the package.)