OT: rsync question

[Nifty Hat Mitch]

On Fri, Jan 21, 2005 at 04:21:20PM -0500, James Pifer wrote:
> Reply-To: For users of Fedora Core releases <fedora-list at redhat.com>
> 
> Quick rsync question. I have a whole bunch of data that I rsync to
> another machine for backup purposes. I had to rebuild the primary system
> and I copied all the data back to it from the backup. Now when I run the
> rsync script it wants to recopy everything, even though it's already
> there on both the primary and backup system. 
> 
> Are there any options on rsync to tell it to look at what's already
> there and figure that out without recopying the whole thing? I looked at
> the options and it wasn't obvious to me how to do this. 

The date time stamps on the 'primary' system are newer so the all the
files look 'new'.  Look at the eight different ways of using rsync as
outlined in the man page.

These flags might help
     --checksum
     --no-whole-file
     --ignore-times

By way of example:
      -c, --checksum
              This forces the sender to checksum all files using a
              128-bit MD4 checksum before transfer. The checksum is
              then explicitly checked on the receiver and any files of
              the same name which already exist and have the same
              checksum and size on the receiver are not transferred.
              This option can be quite slow.

Caution... --delete flag  can cause people in your situation 
trouble, but has it's place.

      --delete	 delete files that don’t exist on sender

It is possible to wack a backup with this option.  i.e. if you are
backing up a gull dir and the contents of the dir get wacked the
mirror will too.  It WILL synchronize the two ;-)


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