How do I find out which package owns a file?

user@host:~$ dpkg-query -S /bin/bash 
bash: /bin/bash

Where bash is the package name.

To do this without installing any extra packages, run

user@host:~$ dpkg-query -S /bin/bash 
bash: /bin/bash

where bash is the package name.

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Alternatively, there are several utilites in Debian which perform this task; check this page for a description. I'll mention two of them, apt-file and dlocate.

apt-file searches its internal cache, thus allowing you to not install all the packages you want to search. Below you will find more detailed guide.

dlocate is a fast alternative to dpkg -L (the command that lists package contents), and as so, it searches only installed packages. Search is performed by dlocate -S file.name.

Also you can search packages online using packages.debian.org server (the Search the contents of packages section).

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Installing and using apt-file

It's a good idea to update first:

sudo apt-get update

See what apt-file is for:

apt-cache show apt-file

Install it:

sudo apt-get install apt-file

Read data from repositories (this works also without sudo but creates user's cache then; with sudo the cache is system-wide):

sudo apt-file update

Perform search. In this example we want to know in which package xrandr executable is:

apt-file search xrandr

It lists many packages with unxrandr, lxrandr.mo or source_lxrandr.py. Not very useful in our case. More clever search:

apt-file search -x /xrandr$

($ denotes end of line). Example output:

bash-completion: /usr/share/bash-completion/completions/xrandr
x11-xserver-utils: /usr/bin/xrandr

The first result doesn't look like executable, the second one does. We can investigate further. Run:

apt-cache show x11-xserver-utils

Bingo! This is the package.

Another alternative:

$ dpkg -S /bin/bash
bash: /bin/bash

On my Ubuntu at least, both seem to be in the dpkg package, so no real advantage to any specific one...