mtime vs ctime

Andrej andrej.groups at
Tue Sep 8 03:10:07 UTC 2015

On 8 September 2015 at 13:57, Kevin Korb <kmk at> wrote:
Hi Kevin.

> Hash: SHA1
> The ctime will always be newer or the same as the mtime.  This is
> because changing the mtime also changes the ctime as does other things
> like changing the permissions.
> Rsync only pays attention to the mtime because rsync can set a
> specific mtime (--times) but setting a specific ctime is impossible as
> it would violate the basic *nix security model.  Therefore ctime can't
> be copied, therefore ctime can't ever be expected to match, therefore
> it is useless to rsync.

If this is the case I don't understand the behaviour I'm
seeing here.  The files mtime haven't changed, the
time-stamps of the copies on the backup server and
the time-stamp on the iSCSI mount are the same (the
mtime, that is; the ctimes differ, obviously, as all files
have the time-stamp of the mount-event).

Do you have an explanation?

> Rsync should be using the delta transfer algorithm (unless
> - --whole-file) so it really should just be determining what is
> different about the file then transferring those differences.  --stats
> would help determine this.

Hmmmm ...

Doesn't look like it to me.

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