If you work with Ubuntu, Debian or Fedora, as soon as you have your default installation, you will probable have nslookup utility installed, but, if you are like me, working on Arch Linux, you will have to install it.
Just enter this.
sudo pacman -S dnsutils
And you will nslookup and other dns utilities ready to run.
The GNU Core Utilities, the basic file, shell and text manipulation utilities of the GNU operating system, is now at version 8.20. GNU Core Utilities 8.20 is just a bug fix release and it includes a very important regression fix for cp since 8.11, where cp could corrupt copies on very fragmented sparse input files.