man rsync snippet
Posted by Anonymous on Sun 12th Jul 2015 11:20
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       --inplace
              This  option  changes  how rsync transfers a file when its data needs to be updated: instead of the default method of creating a new copy of the file and moving it into place
              when it is complete, rsync instead writes the updated data directly to the destination file.

              This has several effects:

              o      Hard links are not broken.  This means the new data will be visible through other hard links to the destination file.  Moreover,  attempts  to  copy  differing  source
                     files onto a multiply-linked destination file will result in a "tug of war" with the destination data changing back and forth.

              o      In-use binaries cannot be updated (either the OS will prevent this from happening, or binaries that attempt to swap-in their data will misbehave or crash).

              o      The fileâ€™s data will be in an inconsistent state during the transfer and will be left that way if the transfer is interrupted or if an update fails.

              o      A  file  that  rsync  cannot write to cannot be updated. While a super user can update any file, a normal user needs to be granted write permission for the open of the
                     file for writing to be successful.

              o      The efficiency of rsyncâ€™s delta-transfer algorithm may be reduced if some data in the destination file is overwritten before it can be copied to a  position  later  in
                     the file.  This does not apply if you use --backup, since rsync is smart enough to use the backup file as the basis file for the transfer.

              WARNING: you should not use this option to update files that are being accessed by others, so be careful when choosing to use this for a copy.

              This  option  is  useful for transferring large files with block-based changes or appended data, and also on systems that are disk bound, not network bound.  It can also help
              keep a copy-on-write filesystem snapshot from diverging the entire contents of a file that only has minor changes.

              The option implies --partial (since an interrupted transfer does not delete the file), but conflicts with --partial-dir and --delay-updates.  Prior to rsync  2.6.4  --inplace
              was also incompatible with --compare-dest and --link-dest.

       --append
              This  causes  rsync  to update a file by appending data onto the end of the file, which presumes that the data that already exists on the receiving side is identical with the
              start of the file on the sending side.  If a file needs to be transferred and its size on the receiver is the same or longer than the size on the sender, the file is skipped.
              This  does  not  interfere with the updating of a fileâ€™s non-content attributes (e.g. permissions, ownership, etc.) when the file does not need to be transferred, nor does it
              affect the updating of any non-regular files.  Implies --inplace, but does not conflict with --sparse (since it is always extending a fileâ€™s length).