Aw: rsync show files changed during transfer - how?

Fabian Cenedese Cenedese at
Mon Dec 19 16:09:10 UTC 2016

At 17:00 19.12.2016, devzero at wrote:

><snipp> But the filename twice can happen under other circumstances; if you've seen this happen, it's almost certainly because the file changed during transfer. Rsync does no locking. Which means that: if you are modifying a file while it's being transferred, then probably the checksum will fail and it'll go round again. And if it goes around twice, and it still fails, then it prints a message saying; Error, checksum failed, file changed during transfer? And it's probably a file like a log file that's being constantly updated and so the checksums didn't match because it's never going to be able to get it exact; it means that what you've got on the other end is something which will approximate some snapshot of the file, but because it's not doing any locking, it can't guarantee that it's got a particular snapshot of the file, because you can't have an atomic read of the whole file. [31m, 49s] <snipp>
>nope, this is wrong, there is no message "checksum failed"

Actually rsync does that (from a log on our server):
WARNING: PUBLIC_SERVER_BACKUP/wiki/data/index/i10.idx failed verification -- update retained (will try again).

So it did recognize a change and synched it a second time. Don't know what happens
if the file changes again though.

>to be a valuable backup solution, i`d like some networker a`like behaviour which gives "file changed during save"
>i wonder what`s so difficult for rsync to "look" at the timestamp or checksum a second time after transfer and if it changed it should spit out a warning....
>isn`t this something which _could_ be implemented, if somebody is able to do ist ?

Maybe it's a question of informational flags (-v, --progress, --stats etc).

bye  Fabi

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