Unix rsync command
Alternative to cp
rsync -HAaux --delete --progress <dir1>/ <dir2>
where you can prepend either <dir1> or <dir2> with a prepending
"<host>:" spec for remote rsync(1)...
the above will maintain hard links, ACLs, and such...
i guess i should actually run down the flags to give you some
background:
-H - preserve hard links
-A - preserve ACLs
-a - archive (i.e. preserve most other stuf and do
a recursive copy)
-u - update-only, do not overwrite newer files
-x - one filesystem (which implies NOT following symbolic
links in the copy)
--delete - prune (delete files in the destination that
don't exist in the source, so you won't want
to use this flag if other products are already
installed)
--progress - show you what's happening in a meaningful way
and... perhaps the most important thing to remember is to always
add the trailing slash to the source (but not the dest) directory...
as that indicates you want to sync the actual absolute locations,
instead of making a copy of the source INSIDE the dest...
rsync(1) is more powerful than cp(1) and it uses SSL-encryption (via SSH) for any data transfers over a network.

