Quick description of the used rsync parameters

        -a, --archive               archive mode; equals -rlptgoD (no -H,-A,-X)

        -r, --recursive             recurse into directories
        -l, --links                 copy symlinks as symlinks
        -p, --perms                 preserve permissions
        -t, --times                 preserve modification times
        -g, --group                 preserve group
        -o, --owner                 preserve owner (super-user only)
        -D                          same as --devices --specials

        -x, --one-file-system       don't cross filesystem boundaries
            --numeric-ids           don't map uid/gid values by user/group name
            --stats                 give some file-transfer stats

        -H, --hard-links            preserve hard links

            --link-dest=DIR         hardlink to files in DIR when unchanged

EXIT VALUES
       0      Success
       1      Syntax or usage error
       2      Protocol incompatibility
       3      Errors selecting input/output files, dirs
       4      Requested action not supported: an attempt was made  to  manipu-
              late  64-bit files on a platform that cannot support them; or an
              option was specified that is supported by the client and not  by
              the server.
       5      Error starting client-server protocol
       6      Daemon unable to append to log-file
       10     Error in socket I/O
       11     Error in file I/O
       12     Error in rsync protocol data stream
       13     Errors with program diagnostics
       14     Error in IPC code
       20     Received SIGUSR1 or SIGINT
       21     Some error returned by waitpid()
       22     Error allocating core memory buffers
       23     Partial transfer due to error
       24     Partial transfer due to vanished source files
       25     The --max-delete limit stopped deletions
       30     Timeout in data send/receive
       35     Timeout waiting for daemon connection

rsync -axH --stats --numeric-ids \
  --link-dest=/backup/server/2015.12.01-11\:10/ \
  server:/ \
  /backup/server/2015.12.01-11\:15/
