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:
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.
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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:
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