[dm-crypt] cryptsetup-reencode: LUKS-${UUID}.new is too small

PePa peter at passchier.net
Fri Mar 14 17:39:05 CET 2014

Arno Wagner <arno at ...> writes:
> The IO error is worrying though, it should _not_ happen.
> Have a look into the system error log to see if this is 
> some lower-level error. It may also be some problem 
> with your LVM setup. (I cannot help there, in my opinion
> LVM is too complicated and causes more trouble than it
> has benefits.)
> Arno

I have no idea what the IO error signifies, as the system is still
functioning normal (I left it on, in case).
But I am convinced this error cannot have anything to do with the LVM setup,
as it is happening on a lower layer. I have not had a bad experience with
LVM ever in the last 7 years since I started deploying it, and I don't know
what trouble you have had with it (or heard about), but I think for now I
will keep using it.

I am wondering though, if it would be a good idea to change the default luks
header size, even if only a smaller header is required according to the
parameters. If by default a header size is chosen that could accommodate a
reencrypt to a larger size, all the shifting doesn't need to happen, and it
will only cost you a few MiBs, which is a small price to pay when usually
you're dealing with at least GiB at this level.


> On Fri, Mar 14, 2014 at 08:59:28 CET, PePa wrote:
> > Reporting back, I did:
> > cryptsetup-reencrypt -c aes-xts-plain64 -s 512 -h sha512
> > --reduce-device-size 4MiB /dev/sda4
> > 
> > It stopped here:
> > Progress: 99.4%, ETA 02:48, 710848 MiB written, speed 27.0 MiB/s
> > IO error during reencryption.
> > 
> > Curiously, I did:
> > cryptsetup luksOpen /dev/sda4 secret
> > 
> > Output>:
> > Device /dev/sda4 is not a valid LUKS device.
> > 
> >  Is there anything I can still try to salvage this situation??
> > 
> > Thanks,
> > Peter
> > 
> > 
> > _______________________________________________
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> > dm-crypt at ...
> > http://www.saout.de/mailman/listinfo/dm-crypt

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