$ sudo apt-get update
$ sudo apt-get install iscsitarget-source 

iscsitarget-source is installed in your system.

Make ensure the iscsitarget-source package were installed using the commands given below,

$ sudo dpkg-query -l | grep iscsitarget-source *

You will get with iscsitarget-source package name, version, architecture and description in a table

iscsitarget-source package basic information: