$ sudo apt-get update
$ sudo apt-get install libldns1-dbg 

libldns1-dbg is installed in your system.

Make ensure the libldns1-dbg package were installed using the commands given below,

$ sudo dpkg-query -l | grep libldns1-dbg *

You will get with libldns1-dbg package name, version, architecture and description in a table

libldns1-dbg package basic information: