http://netbsd.i2p/docs/guide/en/preface.html
You should know, for example, what a
file and a directory are, and how to use an editor. There are plenty
of books explaining basic Unix and operating system concepts, and you
should consult one if you need more background information.
It is better to choose a general book and avoid titles like “ Learning Unix-XYZ, version 1.2.3.4 in 10 days ” , but this
is a matter of personal taste.