did you READ THE WARNING that the kali devs posted !!!!!!
in the "is kali right for you"
As the distribution developers, one would likely expect us to recommend that everyone use Kali Linux. The fact of the matter is however, that Kali is a Linux distribution specifically geared towards professional penetration testing and security auditing and as such, it is NOT a recommended distribution for those unfamiliar with Linux.
In addition, misuse of security tools within your network, particularly without permission, may cause irreparable damage and result in significant consequences.
If you are looking for a Linux distribution to learn the basics of Linux and need a good starting point, Kali Linux is not the ideal distribution for you. You may want to begin with Ubuntu or Debian instead.
kali is a very special distro
designed FOR EXPERTS BY EXPERTS
basically you , the user, should already be able to FROM MEMORY write a install guide all on your own
the basics like installing you should already KNOW BETTER than the back of your hand
and by expert i do mean some one that is a grad or postgrad in network SECURITY
you might want to reread the install docs
they are not much
BUT you are expected to already know all that information
as to external drive
i would use an encrypted usb thumb drive with persistence
but Kali is a single user OS
it ONLY has the root user
-- BE WARNED!!!!
running x11 as root is normally a VERY BAD IDEA