On Tue 08 May 2007, Atte Peltomaki wrote: > > I'm seeing a weird problem with rsync 2.6.9 protocol version 29 on > Debian Sarge. When copying a file from one location to another between > two Debian boxes, if destination includes a file with same size and > name, rsync fails to see that they are not exactly the same file. > > The situation originates from copying a file to a place which is > periodically rsynced onwards, and the rsync coperation takes place before > the original file transfer to the rsync source is complete. > > Example: > > Source: > > md5sum: > 2ac4a4ad88da17f49d26c9e578ce5432 somefile.exe > sha1sum: > eaabb30b716e993be000b89208e2d9f63e78f052 somefile.exe > ls -l: > -rwxrw---- 1 user group 109819105 Apr 2 10:48 somefile.exe* > > Destination: > > md5sum: > 72c116866a75f859a19a150216768e52 somefile.exe > sha1sum: > 33b7d91fc6bd2a5bff292258c7d6eeb7db0aec8a somefile.exe > ls -l: > -rwxrw---- 1 user group 109819105 2007-04-02 10:48 somefile.exe*
The files apparently both have the same size, timestamp, and other attributes. Only the contents differ. > rsync is executed from the source with following flags: > > -alvv --delete --exclude-from=file > > where 'file' includes three lines: > /upload > /upload/* > upload/ > > rsync itself says about somefile.exe: > > somefile.exe is uptodate > > As you can see, md5sums and sha1sums reveal that the file is not the > same, even though timestamps and sizes match. You did not ask rsync to checksum the files... > What is the exact algorithm rsync uses to determien wether a file is up > to date or not? Hmmm.... I thought this would have been in the manpage, but it's not spelled out apparently. Rsync by default compares size and mtime to determine whether a file needs to be transferred. (I think the other attributes such as owner, permissions are only updated, but don't necessarily incur a contents sync, although I confess I'm not absolutely sure.) You need to supply the --checksum option if you want to make sure that the contents are indeed identical. This is normally not done as that would cause a massive IO load; cases that size and timestamp are identical but not the contents don't usually happen... Paul Slootman -- To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
