On 5/9/07, Dave Dykstra <[EMAIL PROTECTED]> wrote:
What does it really mean to preserve access times? When rsync reads a file to copy it, it will change the access time just because it is reading it, so the backup should then have the correct access time, the time the backup file was created.
I tested HEAD of rsync + atimes.diff and it indeed behaves this way, which is silly: rsync destroys the data it is told to preserve! The atimes.test doesn't catch this because it uses a zero-length file, so there is no read to actually hit the atime.
Some tools have an option to reset the access time of the file they copy, but in so doing the tools update the inode change time of the input file which is generally more important to users than access time. It is not possible to preserve both as a filesystem user like rsync.
It is possible on some filesystems to read a file without hitting its atime by opening it with O_NOATIME. The same issues apply to GNU tar, so there was an extensive discussion on the bug-tar mailing list of how not to destroy atimes of source files (including use of O_NOATIME): http://lists.gnu.org/archive/html/bug-tar/2005-09/msg00035.html Personally, I don't like access times because they're impure in the sense that reading shouldn't write and as far as I know they don't have any important uses. All of my computer's filesystems are mounted noatime. Matt -- To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
