been around for several releases.

              This option was added in rsync 3.2.3.  This  version  also  began
              the  forwarding  of  a  non‐default  setting  to the remote side,
              though rsync uses the backward‐compatible  options  --msgs2stderr
              and  --no‐msgs2stderr  to  represent the all and client settings,
              respectively.  A newer rsync will continue to accept these  older
              option names to maintain compatibility.

       --quiet, -q
              This  option  decreases  the  amount of information you are given
              during the transfer,  notably  suppressing  information  messages
              from  the  remote  server.   This  option is useful when invoking
              rsync from cron.

       --no‐motd
              This option affects the information that is output by the  client
              at  the start of a daemon transfer.  This suppresses the message‐
              of‐the‐day (MOTD) text, but it also affects the list  of  modules
              that  the  daemon sends in response to the "rsync host::" request
              (due to a limitation in the rsync protocol), so omit this  option
              if you want to request the list of modules from the daemon.

       --ignore‐times, -I
              Normally rsync will skip any files that are already the same size
              and  have the same modification timestamp.  This option turns off
              this "quick check" behavior, causing all files to be updated.

              This option can be confusing compared  to  --ignore‐existing  and
              --ignore‐non‐existing  in  that that they cause rsync to transfer
              fewer files, while this option  causes  rsync  to  transfer  more
              files.

       --size‐only
              This  modifies  rsync’s "quick check" algorithm for finding files
              that need to be transferred, changing  it  from  the  default  of
              transferring  files with either a changed size or a changed last‐
              modified time to just looking for  files  that  have  changed  in
              size.   This is useful when starting to use rsync after using an‐
              other mirroring system which may not preserve timestamps exactly.

       --modify‐window=NUM, -@
              When comparing two timestamps, rsync treats the timestamps as be‐
              ing equal if they differ by no more than the modify‐window value.
              The default is 0, which matches just  integer  seconds.   If  you
              specify  a  negative  value (and the receiver is at least version
              3.1.3) then nanoseconds will also be taken into account.   Speci‐
              fying  1 is useful for copies to/from MS Windows FAT filesystems,
              because FAT represents times with a 2‐second resolution (allowing
              times to differ from the original by up to 1 second).

              If you want all your transfers to default to  comparing  nanosec‐
              onds, you can create a ~/.popt file and put these lines in it:

                  rsync alias ‐a ‐a@‐1
                  rsync alias ‐t ‐t@‐1

              With that as the default, you’d need to specify --modify‐window=0
              (aka  -@0)  to override it and ignore nanoseconds, e.g. if you’re
              copying between ext3 and ext4, or if the receiving rsync is older
              than 3.1.3.

       --checksum, -c
              This changes the way rsync checks if the files have been  changed
              and are in need of a transfer.  Without this option, rsync uses a
              "quick  check"  that  (by default) checks if each file’s size and
              time of last modification match between the sender and  receiver.
              This  option  changes this to compare a 128‐bit checksum for each
              file that has a matching size.  Generating  the  checksums  means
              that  both  sides  will