This is on Mac OS X Lion, and I use the following to back up a project folder
cp -Rp ~/foo /Volumes/KINGSTON
cp -a ~/foo /Volumes/KINGSTON
-a is so that the timestamps of the files are preserved. (KINGSTON is the USB flash drive, and Get Info says I have permission to read and write on this device).
But it will give many errors such as:
cp: chflags: /Volumes/KINGSTON/Proj/Proj/Color.h: Invalid argument
Can this be fixed? thanks.