Date: Mon, 17 Oct 2011 11:29:23 -0700 From: Garrett Cooper <yanegomi@gmail.com> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: Xin LI <delphij@gmail.com>, freebsd-geom@freebsd.org Subject: Re: GELI devices produced with 9.0+ fail when mounted on 8.2, etc? Message-ID: <CAGH67wRSVtsophbJ4cF5Y2x=5a9HHB5_SE6HqvwwyjyVtUd9oA@mail.gmail.com> In-Reply-To: <20111017132945.GG1679@garage.freebsd.pl> References: <924643A0-0798-4FAC-8F82-4AFBC56DC8D7@gmail.com> <CAGMYy3tX=Xr1k%2B=7FqV5=Ddooopodtmv1hG=zy5G2Ye5KCuO_Q@mail.gmail.com> <7EC93C28-6405-443F-92C6-0291F8D88995@gmail.com> <CAGMYy3veJQ-pBg1BuAZyH3rvMxEaFQOYPTJYgWPteohw-HE%2BuA@mail.gmail.com> <EDE63E3A-A2BF-4422-B0F5-8DB4AFE5B573@gmail.com> <20111017132945.GG1679@garage.freebsd.pl>
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On Mon, Oct 17, 2011 at 6:29 AM, Pawel Jakub Dawidek <pjd@freebsd.org> wrot=
e:
> On Sun, Oct 16, 2011 at 11:36:29PM -0700, Garrett Cooper wrote:
>> On Oct 16, 2011, at 7:51 PM, Xin LI wrote:
>> > Backward compatibility is that you can expect what's working in an
>> > older version of FreeBSD would just work on a newer version of
>> > FreeBSD, not the contrary.
>>
>> =A0 =A0 =A0 Perhaps, but the fact that this behavior / set of expectatio=
ns isn't clearly called out in the geli manpage -- and the fact that there =
isn't official versioning (or at the very least this isn't made a requireme=
nt based on the output above) associated with each metadata format is a fau=
lt that should be corrected. Otherwise, how can GELI be considered a viable=
mechanism for encrypting data across multiple versions of FreeBSD? It seem=
s very shortsighted that there isn't at least a mechanism for reading -- or=
at least rejecting -- later versions of metadata in an intuitive manner.
>> =A0 =A0 =A0 FWIW if you use geli from an earlier version of FreeBSD (hin=
t: chroot, jail), it does the right thing.. which means that I have a means=
for producing encrypted images on later versions of FreeBSD now. Neverthel=
ess, having to do so in such a roundabout manner is annoying and I'm sure I=
won't be the only one that will be affected by this.
>
> Thanks Garrett for your comments.
>
> As Xin pointed out, GELI is not forward compatible, but is backwards
> compatible (GELI device initialized on FreeBSD 8.x will work on 9.x, but
> this may not be true the other way around).
>
> I fully agree that the error should be clear on what exactly is wrong
> and this should be easy to fix.
>
> As for creating forward compatible GELI devices I think the right thing
> to do here is to:
> 1. Add '-V version' option for 'geli init' subcommand that will allow to
> =A0 specify metadata version number to use for device initialization.
> 2. Add 'geli upgrade [-V <version>] [prov ...]' subcommand that will
> =A0 allow to upgrade the given device to the given metadata version (only
> =A0 to version greater than the current version). If only providers are
> =A0 given, but -V is not given, metadata of the given providers would be
> =A0 upgraded to the latest version support by the system.
> =A0 Would be nice if backup file could be also upgraded.
> =A0 If 'geli upgrade' is executed with no arguments a list of supported
> =A0 metadata versions with some short description and ideally FreeBSD
> =A0 versions that can run the given GELI version will be printed.
> 3. Print metadata version in 'geli list' output.
That suggestion's brilliant. All that we need now is a short blurb
in the manpage describing when which metadata was implemented when and
I think this will be on the right track.
Thanks a bunch!
-Garrett
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