Using rsync for backup trashes st_atime

[Jan-Benedict Glaw]

On Thu, 2002-10-24 04:04:14 -0700, jw schultz <jw at pegasys.ws>
wrote in message <20021024040414.A6256 at pegasys.ws>:
> On Thu, Oct 24, 2002 at 12:16:26PM +0200, Jan-Benedict Glaw wrote:
> > I think '--preserve-server-atime' would be a nice additional feature,
> > and I tend to implement it on monday or so. I haven't yet looked at the
> > source, so there may be already a solution to this problem. If you think
> > this is a nice feature, please give some response...
> 
> .from rsync3.txt by Martin Pool
> |  - Propagate atimes and do not modify them.  This is very
> |    ugly on Unix.  It might be better to try to add
> |    O_NOATIME to kernels, and call that.

It's not yet there, and SUSv3 doesn't propose it either...

> It would be better to call it --reset-access-time as cpio
> does.  Not only to make it easier to remember (for those

I don't care about the feature's name. So I'll use --reset-access-time
or --atime-preserve (as tar does).

> using other tools) but to make it clear that the access time
> is being reset to a value that will not reflect accesses by
> other activity between initial stat and the final reset.
> 
> Beyond that I don't much care.  All my filesystems are mounted -o
> noatime,nodiratime for efficiency.

However, you're loosing data by this:-) You can't tell when some last
access has happened...

> Personally, i think any MUA that depends on atime is broken by design.

You're using one of them. Despite that, MUAs come to my mind which might
want to use st_atime. But there might exist other applications as well.
This is why I care about the issue. My st_atimes will be correct some
minutes later (as I receive huge amounts of email), though.

MfG, JBG

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