[Bug 1659950] Re: rsync -u --inplace --partial -a can't resume transfer

[Paride Legovini]

Hello Nahuel,

According to your reasoning I assume the "root" issue should still
affect the versions of rsync shipped with the newer Ubuntu releases.

I agree it would be nice for the behavior you describe to be documented,
but I don't think it's worth patching the Ubuntu package for it. I
recognize we have a papercut here, but I don't think the fix for it
belongs to Ubuntu; it should instead be driven (and thus also validated)
upstream. For this reason I'm marking this bug as a Won't Fix. Should
you disagree with my assessment please comment back and set the bug
status back to New, we'll look at it again. Thanks!

** Changed in: rsync (Ubuntu)
       Status: Triaged => Opinion

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Title:
  rsync -u --inplace --partial -a can't resume transfer

Status in rsync package in Ubuntu:
  Opinion

Bug description:
  Suppose you have a file in hostA:

    hostA$ ls -l /tmp/files
     -rw-rw-r-- 2 root root 563016 Jan 10 15:01 test.txt

  You download it from the hostB using:

    hostB$ rsync -u --inplace --partial -a hostA::files/* .

  If the transfer is aborted, hostB will get only a partial file:

    hostB$ ls -l /tmp/files
     -rw-rw-r-- 2 root root   2024 Jan 11 18:00 test.txt
    
  BUT the ctime/mtime of hostB/test.txt now is NEWER than hostA/test.txt(and mtime == ctime). So, if you run the same rsync -u command again:

    hostB$ rsync -u --inplace --partial -a hostA::files/* .

  Rsync will SKIP THE FILE, because hostB/test.txt is "newer" than
  hostA/test.txt. So you CAN'T resume using rsync -u command, and you
  will think there are no differences.

  To avoid this bug, rsync must create the file with ctime=mtime=0. And
  if the file already exists before transfer, rsync -u must not change
  his current ctime/mtime. Ctime/mtime must be updated ONLY after the
  transfer was successfully completed.

  Note this is really need because there are scenarios where checksum
  comparison can't be used, only comparison by time. For example, to
  avoid deleting changes made in hostB to test.txt. Also I need to use
  --inplace.

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