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Re: Will rsync fix iso-file checksum failure?

On Thu, 26 Nov 2009, Tzafrir Cohen wrote:

On Thu, Nov 26, 2009 at 07:12:35PM +0700, Sthu Deus wrote:
Good day.

I have badly downloaded dvd.iso file w/ Debian - though size is
exactly the same as it should - md5sum check fails...

My question is, Whither rsync can re-download the file in manner that
allows me to redoanload it not (w/ ftp, etc) whole again?

Rsync should check for the checksum of the file.

Furthermore, on a large file it should try to avoid downloading parts of
it if that local part has the same checksum as in the remote.

Tzafrir Cohen         | tzafrir@jabber.org | VIM is
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Missed the part on rsync :)

I never tried repairing a broken file using rsync, but it looks like the option you want is -c:

       -c, --checksum
              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 expend a lot of disk I/O  reading  all  the
              data  in  the  files  in  the transfer (and this is prior to any
              reading that will be done to transfer changed  files),  so  this
              can slow things down significantly.

Whenever you test this, test it on a copy of the bad ISO incase the command
you end up using accidentally deletes it (or starts it over from the


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