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The Thursday 2007-04-26 at 06:45 -0700, Randall R Schulz wrote:
> On Thursday 26 April 2007 04:50, Carlos E. R. wrote:
> > ...
> >
> > The things is, if the modification time is the same, the file data
> > will still be the same
>
> That does not necessarily follow. There is a system call that allows
> user code to arbitrarily change the file time (it's used, in part, by
> backup programs that want to reset the file times of the restored file
> to those that were in effect for the file when it was saved to the
> backup medium).
The command "touch" can do that, of course. But that is not normal usage.
If somebody is "messing up" the timestamps, that his fault :-p
> > and doesn't need to be backed up again. On the
> > other hand, if it has changed, there is a doubt: either check a
> > checksum and decide, or backup regardless.
>
> The point is, the only 100% reliable way to tell if a file has changed
> is to compare it to the original.
Of course.
> A checksum (not necessarily MD5) is
> the next best. Modification time alone is the weakest and least
> reliable way.
People will also tell you that the only good backup is a full backup,
despising incremental backups - for those reasons precisely.
Depends on how "paranoid" you are, but sometimes it's better to just do a
full backup.
- --
Cheers,
Carlos E. R.
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