On Debian systems (and derivatives):

$ dpkg --search /bin/ls coreutils: /bin/ls 

That is, the file /bin/ls belongs to the Debian package named coreutils.

But this only works if the package is installed. What if it's not?

On Debian systems (and derivatives):

$ dpkg --search /bin/ls coreutils: /bin/ls 

That is, the file /bin/ls belongs to the Debian package named coreutils.

But this only works if the package is installed. What if it's not?