> "cd /; tar cf - .??* [a-m]* [o-z]* | (cd nroot; tar xvpf -)" 

As much as I like GNU tar (and I like it a lot), some jobs seem to be
better handled by cpio.  Whenever I have to do this type of copy, I use a
variation on

find -x / -print | sed '/^n/d' | cpio -pvdum /nroot

Of course, the sed command can be modified for whatever, or you can even
split up into two lines and use a temporary file in the middle that you
can tweak (in which case you just cat file | cpio ...). 

I moved and shuffled my partitions around this week, involving two root
partition copies with the cpio command above without a hitch. 

Just my $.02... 

--scott