rsync : file-copying tool
[SYNOPSIS] rsync OPTION SRC DEST
OPTION
-v increase verbosity
-q suppress non-error messages
-a archive mode is -rlptgoD (no -A,-X,-U,-N,-H)
-r recurse into directories
-R use relative path names
-u skip files that are newer on the receiver
-d transfer directories without recursing
-l copy symlinks as symlinks
-L transform symlink into referent file/dir
-k transform symlink to dir into referent dir
-K treat symlinked dir on receiver as dir
-H preserve hard links
-A preserve ACLs (implies --perms)
-n perform a trial run with no changes made
-z compress file data during the transfer
--exclude=PATTERN exclude files matching PATTERN
-delete delete extraneous files from dest dirs