Re: sftp rename not good.

[Dan O'Reilly <dano%process.com@localhost>]

At 03:57 PM 5/13/2003, Alfred Perlstein wrote:
> * Joseph Galbraith <galb-list%vandyke.com@localhost> [030513 12:28] wrote:
> > Let me make sure I understand the problem:
> >
> > - SSH_FXP_RENAME specifies that it is an
> >   error if the new file exists.
> >
> > - rename(2) specifies that if the new file
> >   exists, it is always overwritten.
> >
> > Therefore rename(2) can't be used to implement
> > SSH_FXP_RENAME.
> >
> > Is this a correct summary of the problem?
>
> That's the cause of the problem.
>
> The actual problem is that it doesn't seem possible to do atomic
> updates of files using sftp because of the way SSH_FXP_RENAME must
> be implemented.
>
> Also, I _think_ that using link(2) (without fsync) instead of
> rename(2) allows for the system to lose the file completely
> during an outtage.
>
> I think there should be some way of invoking an actual rename(2)
> on the server.

That would be best, IMHO.  That way, you can implement server-specific
behavior.  For example, those of us on VMS have versioned file systems,
so the behavior of a rename on VMS could be drastically different than
that on a UNIX system.

------
+-------------------------------+----------------------------------------+
| Dan O'Reilly                  |  "There are 10 types of people in this |
| Principal Engineer            |   world: those who understand binary   |
| Process Software              |   and those who don't."                |
| http://www.process.com        |                                        |
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