How to list dependent packages (reverse dependencies)?

Question

In order to research what caused the installation of a given package, I'd like to get a list of packages which depend on that package. I couldn't find anything obvious in man dpkg.

Answer 1

apt-cache rdepends packagename should do what you want

Answer 2

aptitude has a fairly nice way of handling this:

$ aptitude why bash
i   foomatic-filters PreDepends bash (>= 2.05)

By default, it only lists the "most installed, strongest, tightest, shortest" reason, but you can use aptitude -v why to make it output everything it finds.

Answer 3

apt-cache showpkg <pkgname> 

Example:

apt-cache showpkg lightdm

Answer 4

There are more than one way, with each method showing a different output.

For a detailed view of the dependency tree;

aptitude install apt-rdepends
apt-rdepends bash

Alternatively;

apt-cache showpkg bash

Or a concise list:

apt-cache rdepends bash

Answer 5

In addition to other good answers, doing:

sudo apt -s remove <pkgname>

( -s Does a "simulated" removal. )

The removal command will normally list any dependencies/programs/libraries that will be affected or that can removed (orphaned) along with specified pkg. (If they exist.)