[ale] Should filesystems have undelete (was Get paid for undelete on ext3 help)

[Bao C. Ha]

On Fri, Aug 23, 2002 at 09:45:22AM -0400, Geoffrey wrote:

The simplest approach is to patch the system call unlink(), I
think.  Just move the delete stuff into a temprorary area and
flush it after 7 days. 

Versioning requires a different mindset to use it effectively.
When I was using VMS and Genera, I always deleted, flushed, and
moved the version back to 1, while cursing whoever design the
"inconvenient" filesystems.  

The principle of undelete process in a Unix system is the same
as in DOS.  If you can find the first inode intact, I believe
you can just follow it.  Unfortunately, a Linux filesystem is
so dynamic that unless you immediately bring the system down and
remount the file sstem as read-only, you probably loose it
already.

Anyway, I believe Midnight Commander has an undelete feature for
ext2, presumbly it should also work with ext3.  Debian also has
a package called "recover", which can be used to "undelete". 
Supposedly, there is an ext2-undeletion howto, that documents a
recover process.

Bao

> >There are versioning systems like CVS that do some of this, but the user
> >has to explicitly call them--I want something that is the default
> >behavior.  Also, CVS repositories only grow and never recycle their
> >bits; even a "removed" file never gives up it's space in CVS.  I want a
> >system that starts giving space back as it is needed.
> 
> That's quite a request, so when will you be done building it? :)  There 
> are all kinds of issues this could draw.  I'll just throw out one, how 
> do you know what to 'give back' and when it's okay to do so?  Other than 
> notifying the user to backup the undelete area or they can't do anymore, 
> I don't know what the answer is.

-- 
Bao C. Ha                    voice: (310) 980-3805
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