Registered: Apr 2010
Distribution: Debian, Ubuntu, Fedora, RedHat, DSL, Puppy, CentOS, Knoppix, Mint-DE, Sparky, Vsido, tinycore, Q4OS
If he does not need access to any files other than those you place for him to examine, look into IBSH (Iron Bound Shell). With it you can configure EXACTLY what commands the user can execute, and they are ROOTED into their directory tree. What is more, no files in that directory tree can remain executable, links are delinked, etc. to make them VERY well secured.
I modified the source code a while ago to make a version that would allow links out of the home tree to remain. Very nice source, well coded, easy to understand.