rsync is a program for comparing directories and copying files as a result. It can be useful for synchronization.
Because it compares first before copying things, it is much much faster that copying it you have two similar directory structures to start with.
Examples
Local update
rsync -av /path/to/source/ /different/path/to/destination
This copies the entire contents of /path/to/source into /different/path/to/destination, including subdirectories, including timestamps and permissions. This is different from
rsync -av /path/to/source /different/path/to/destination
(note missing trailing slash) which creates a new subdirectory /different/path/to/destination/source
include acls and extended permissions
Many of our linux volumes now include access control lists (ACLs). To make sure everything is copied:
rsync -avAX /path/to/source /different/path/to/destination
v for verbose
-v makes it verbose so you see a list of the files being copied.
Local update making exact copy
rsync -av --delete /path/to/source/ /different/path/to/destination
By default, don't delete
--delete is necessary to get rid of files or directories in destination that were not in source.
Copying over a network with ssh
rsync -av -e ssh /path/to/source/ username@otherbox.brandeis.edu:/different/path/to/destination
This copies the entire contents of /path/to/source into /different/path/to/destination on otherbox.brandeis.edu, authenticating as username.
Steven Karel - 16 Mar 2008