CopyFile copies the regular file at path src to dst.
dst is atomically replaced if it already exists and inherits src's mode.
Ownership will also be preserved if the EUID is 0.
MoveFile moves the file at src to dst.
The source and destination paths may be on different filesystems.
The mode will be preserved, and ownership will also be preserved if possible
(i.e. if called with an EUID of 0 or if moving the file within a filesystem).