Re: ext4 features

From: Valdis . Kletnieks
Date: Thu Jul 06 2006 - 16:50:56 EST


On Thu, 06 Jul 2006 13:27:35 EDT, Ric Wheeler said:

> The key is to keep the signature/checksum with the file - tripwire and
> backup programs could do this (and even store it their own extended
> attribute), but I think that it is more generically useful than that.

Backup programs want it stored with the file. Tripwire wants it stored
as far away from the file as possible. Remember - for Tripwire, we *don't*
want the "current maintained value", we want "the snapshotted value from
a known good state".

If the filesystem stored a "guaranteed trustable current hash", Tripwire
*could* use it to compare against its database rather than having to re-read
the file and recompute it. Unfortunately, a useful trustable hash is
basically incompatible with any sort of incremental updating (except for
the special case of appending to the file).

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