[dm-crypt] btrfs and "requested offset is beyond real size of device"

Arno Wagner arno at wagner.name
Tue Feb 17 14:14:03 CET 2015


On Mon, Feb 16, 2015 at 22:28:54 CET, Jay Sullivan wrote:
> So,
> 
> I must have been doing some step in the wrong order before, because, after
> cleaning up my notes for others to read, it now seems to work fine.  I'm
> still sort of confused why I was running into that error consistently, but
> clearly I'm doing something differently this time.  Attached steps for
> creating full disk encryption with btrfs with Ubuntu 14.10, which worked
> successfully for me.

Interesting. Thanks for reporting the success and the details!

Arno
 
> ----
> ---- Start of steps to reproduce
> ----
> 
> I'm using Ubuntu Desktop 14.10 LiveCD, with only one hard drive in my
> computer: a 32GB flash drive.  (Note: I tried this on a 500GB hard drive as
> well, same results.)  I'm doing all of this offline (as in not connected to
> Internet.)
> 
> I use GParted to partition the flash drive as follows (GPT):
> 
>     /dev/sda1     1MiB      bios_grub     ( < I make sure to set the
> bios_grub flag here )
>     /dev/sda2   256MiB    btrfs         ( /boot )
>     /dev/sda3   6.84GiB   crypt-luks    ( encrypted swap )
>     /dev/sda4   22.82GiB  crypt-luks    ( encrypted / )
> 
> I then format/open the LUKS partitons:
> 
>     cryptsetup luksFormat /dev/sda3
>     cryptsetup luksFormat /dev/sda4
>     cryptsetup luksOpen /dev/sda3 neoswap
>     cryptsetup luksOpen /dev/sda4 neoroot
> 
> I then format all my boot, swap, and root partitions:
> 
>     mkfs.btrfs -f -L neoboot /dev/sda2
>     mkswap -L neoswap /dev/mapper/neoswap
>     mkfs.btrfs -f -L neoroot /dev/mapper/neoroot
> 
> I then run the graphical "Install Ubuntu 14.10" installer from the
> desktop.  When it asks how I want to install, I choose "Something else",
> and tell it to use the following partitioning scheme, instructing it NOT to
> format any partitions (since we already did):
> 
>     /dev/sda2                btrfs    /boot
>     /dev/mapper/neoswap      swap
>     /dev/mapper/neoroot      btrfs    /
> 
> (Note: It will insist on formatting the swap partiton, that's fine.  It
> will insist on installing a bootloader to /dev/sda, that's fine, although
> we will override this step in a second.)  I continue with the installation,
> waiting until the installation is finished.
> 
> At this point, it's possible for me to list all of the partition GUIDs,
> which I'll need for crypttab and fstab:
> 
>     /dev/sda1     1MiB      bios_grub
>     /dev/sda2   256MiB    btrfs         ( /boot )
> UUID=23fa61d2-0b74-465a-be83-e026ebb373bc
>     /dev/sda3   6.84GiB   crypt-luks
> UUID=5d60aeca-6e5d-4a0c-9d28-b31c79213589
>         /dev/mapper/neoswap             ( swap  )
> UUID=ee13478f-b310-4c3c-b14a-579dea9ee25c
>     /dev/sda4   22.82GiB  crypt-luks
> UUID=badb304c-38de-4d04-9456-e9759c3150ab
>         /dev/mapper/neoroot             ( /     )
> UUID=aa67f7ba-08cc-4760-aa30-fa5bc10b88cc
> 
> Once installation is done, and before I restart, I open a root shell and
> chroot into the newly-installed setup:
> 
>     # mount /dev/mapper/neoroot /mnt -o subvol=@
>     # mount /dev/mapper/neoroot /mnt/home -o subvol=@home
>     # mount /dev/sda2 /mnt/boot
>     # mount --bind /dev /mnt/dev
>     # mount --bind /proc /mnt/proc
>     # mount --bind /sys /mnt/sys
>     # mount --bind /etc/resolv.conf /mnt/etc/resolv.conf
>     # chroot /mnt
> 
> Now that I'm in, I update /etc/crypttab as follows:
> 
>     neoswap UUID=5d60aeca-6e5d-4a0c-9d28-b31c79213589 none luks
>     neoroot UUID=badb304c-38de-4d04-9456-e9759c3150ab none luks
> 
> I then update /etc/fstab:
> 
>     UUID=23fa61d2-0b74-465a-be83-e026ebb373bc /boot           btrfs
> defaults,noatime              0       2
>     UUID=ee13478f-b310-4c3c-b14a-579dea9ee25c none            swap
> sw                            0       0
>     UUID=aa67f7ba-08cc-4760-aa30-fa5bc10b88cc /               btrfs
> defaults,noatime,subvol=@     0       1
>     UUID=aa67f7ba-08cc-4760-aa30-fa5bc10b88cc /home           btrfs
> defaults,noatime,subvol=@home 0       2
> 
> Almost done.  Still chroot'ed, I run:
> 
>     update-initramfs -k all -c
>     update-grub
>     grub-install /dev/sda
> 
> I restart my computer, boot into GRUB, and boot with the following:
> 
>     insmod gzio
>     insmod part_gpt
>     insmod btrfs
>     search --no-floppy --fs-uuid --set=root
> 23fa61d2-0b74-465a-be83-e026ebb373bc
>     linux /vmlinuz-3.16.0-23-generic
> root=UUID=aa67f7ba-08cc-4760-aa30-fa5bc10b88cc rootflags=noatime,subvol=@
>     initrd /initrd.img-3.16.0-23-generic
> 
> ----
> ---- End of steps to reproduce
> ----
> 
> I just did this and it booted successfully 15 times in a row.
> 
> Thanks,
> Jay

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> dm-crypt at saout.de
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-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -- Plato

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier


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