mtime vs ctime

Kevin Korb kmk at
Tue Sep 8 01:57:04 UTC 2015

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.

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.

On 09/07/2015 09:46 PM, Andrej wrote:
> Hi,
> We use an rsync (rrsync, to be precise) based back-up solution.
> Every so often an iSCSI based file-system gets brought up and left
> connected for the night. After a mount event rsync will back that
> volume up, including server TB of data that haven't been modified,
> but the ctime is newer than the mtime.  Is there a way to stop
> this behaviour?
> Cheers, Andrej

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