rsync: "-c" option clarification
kmk at sanitarium.net
Thu Mar 23 20:10:17 UTC 2017
Before anyone yells at me, yes, you can use rsync's --checksum to detect
(and fix) files that are incorrect despite having correct timestamps and
sizes. This would mean that a previous rsync had been corrupted not the
current one. But it is important to note that this would only be
reported to you if you also use --itemize-changes and what to look for
(a file with a c but not an s or a t).
It is also worth noting that single file compression tools (like gzip)
automatically set the original mtime when compressing or decompressing.
If you decompress then recompress such a file you can cause a case of a
file with matching mtime+size but not matching checksum due to gzip's
metadata even though the uncompressed result is identical. I would not
consider this to be a case worth updating the remote copy but I am sure
someone will disagree.
On 03/23/2017 03:49 PM, Kevin Korb via rsync wrote:
> The -c option causes rsync to checksum EVERY file on both ends BEFORE
> rsync does anything else. It checksums files that are on only 1 end.
> It checksums files that are different sizes. It will not catch a
> hardware problem preventing rsync from writing a file correctly.
> On 03/23/2017 03:12 PM, steven banville via rsync wrote:
>> I am using "rsync" to send files from a source machine to a remote
>> machine as one typically does. I would like to clarify that the "-c"
>> option will cause the checksum on the receiving end to be created by
>> reading the already written file and NOT the data stream on the
>> receiving end. This would help in catching disk I/O errors if the
>> checksum is done on the file on disk.
>> I understand if the size and (or date?) don't match, the checksum is not
>> needed on the receiving end.
>> I may be missing something but it wasn't entirely clear to me that the
>> checksum is done based on the file on disk.
Kevin Korb Phone: (407) 252-6853
Systems Administrator Internet:
FutureQuest, Inc. Kevin at FutureQuest.net (work)
Orlando, Florida kmk at sanitarium.net (personal)
Web page: http://www.sanitarium.net/
PGP public key available on web site.
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 224 bytes
Desc: OpenPGP digital signature
More information about the rsync