173

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.

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  • Related: askubuntu.com/questions/13296/… – Seth♦ Feb 26 '15 at 3:58
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    The older question's answers all revolve around aptitude, something that hasn't been installed by default for years. In 2017, everyone on Ubuntu still has apt-cache. Anyone who follows the linked question is going to get lost in a discussion about a program few will have. – Lambart Aug 18 '17 at 17:48
216

apt-cache rdepends packagename should do what you want

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    Excellent! apt-cache rdepends tofrodos confirmed the suspicion that it was installed by another package (the obsoleted dos2unix). – l0b0 Apr 30 '12 at 13:12
  • Good deal. I do wish there was a recursive option. Sadly there is not as far as I am aware. – RobotHumans Apr 30 '12 at 13:27
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    As for today (apt version 0.9.9.1), there is --recurse option that works with rdepends. – jarno Dec 22 '13 at 14:00
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    If you add --installed, the output is even useful for packages which can be used by many others: apt-cache rdepends --installed packagename – quazgar May 27 '14 at 22:08
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    For the output, why do some of the packages have a vertical bar (pipe symbol) before them? – Vahid Pazirandeh Nov 16 '17 at 5:35
54

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.

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  • 4
    Seems like it considers only the installed packages, not everything available. And that was what I needed. – Tuukka Mustonen Jul 25 '13 at 10:06
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    For that you want reverse-depends in ubuntu-dev-tools – tumbleweed Jul 25 '13 at 11:38
  • How about debian? – Tuukka Mustonen Jul 25 '13 at 12:08
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    ubuntu-dev-tools is in Debian – tumbleweed Jul 26 '13 at 11:18
  • This is great. I learned that openssh-server recommended (and therefore installed) xauth on a headless server, dragging in hundreds of x11 dependencies and dozens of useless updates a month. That's the problem with automated package management! – BaseZen Mar 2 '18 at 3:17
16
apt-cache showpkg <pkgname>

Example: 

apt-cache showpkg lightdm
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14

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

For a detailed view of the full reverse dependency tree; 

aptitude install apt-rdepends
apt-rdepends -r bash

Alternatively;

apt-cache showpkg bash

Or a concise list: 

apt-cache rdepends bash
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  • What exactly does rdepends show in that tree? apt-rdepends php7.0-fpm shows sed. sed doesn't depend on PHP, let alone PHP FPM. – Dan Dascalescu Jan 9 '18 at 23:21
  • It is reverse depends, it means that PHP depends on sed. – Erik Berkun-Drevnig Apr 25 '18 at 3:30
  • Hi guys, actually "apt-rdepends" stands for "recursive dependency". If you want reverse recursive dependency, you have to type : apt-rdepends -r yourPackageNameHere – SebMa Apr 27 '18 at 12:56
  • The apt-cache man page says "rdepends shows a listing of each reverse dependency a package has". Whereas apt-rdepends requires the -r option to do reverse dependencies, as @SebMa says. – Anil G Feb 5 at 3:16
4

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.)

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  • apt remove -s php7.0-fpm shows The following additional packages will be installed: apache2 apache2-bin apache2-data libapache2-mod-php7.0 libaprutil1-dbd-sqlite3 libaprutil1-ldap liblua5.1-0. Why would apache get installed if I remove PHP FPM? – Dan Dascalescu Jan 9 '18 at 23:22
  • @DanDascalescu Hmm. Might be a bad install/remove script for apt pkg or might be you have some other dependencies that install apache2 as dep (meaning a webserver is needed - and I believe apache2 is default web server). Could be a few things. Just not sure. Has the smell of a good post on AskUbuntu if you haven't found an answer. – bshea Jul 10 '18 at 16:26
4

The simplest option is still:

apt rdepends package-name

which does not require you to install any package.

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  • 1
    What is this adding to the accepted answer? – l0b0 Nov 26 '18 at 23:58
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    The accepted answer has nothing to do with this one. The output is completely different and way more useful for human consumption than apt-cache's. The answer mentions that apt-cache is not installed by default everywhere - that alone should be a rather good hint why this answer has its purpose. finally, this is actually the answer I was looking for, so any downvote is rather silly. – stefanct Nov 28 '18 at 13:21
  • One very significant reason why this is better than the accepted version is that it includes the version of the dependencies, unlike apt-caches output. It's exactly what I needed right now (debugging a glibc 2.28 incompatibility, so upvoting) – Per Lundberg Jan 2 at 9:10
  • upvote for using just apt. at the time of the original answer, I'm not sure this just apt solution would have been valid, but if it is now, that's good. – RobotHumans Apr 20 at 11:53

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