[Bug 1383948] Re: Ubiquity Installer doesn't recognize existing btrfs partitions

[Phillip Susi]

On 10/29/2014 07:04 PM, Damiön la Bagh wrote:
> BTRFS is really easy to add or subtract a disk. Grub2 has no
> problem with it and I can still boot after the disk has been added
> and balanced.

Wow... last I saw they had trouble fitting code to do a simple single
disk case into 64k and were asking about increasing that size.  To
handle multiple disks and still fit in 64k is nothing short of miraculous.

> As for other operating systems. This is a moot point, the scenario
> is using Ubuntu+Btrfs with physical SSD's. If the disks need to be
> converted back to legacy partition table format it's as simple as
> writing a few 00's to the first 64kib with dd. dd if=/dev/zero
> of=/dev/sdX count=64

I meant sharing part of the drive, rather than blowing it all away.
With a partition table you can always fire up gparted and shrink down
the btrfs partition and make a new one if you need it.  I even patched
things to do this while the volume is mounted a while back ;)

> For UEFI, I've already complained to the UEFI bord that they are
> holding back technology by insisting on using a 1980's file system
> to hold UEFI. It's the most ridiculous 'invention' in computers in
> the last 10 years. I understand the want and need to kill the BIOS
> but there are much more graceful solutions then defaulting to 30+
> year old legacy tech.

It's about as simple as filesystems get, everyone already supports it
and it doesn't really have any drawbacks that matter in a pre boot
environment, so it was a no brainer rather than inventing a whole new
filesystem or mandating that different parties adopt an existing
filesystem of another.  Implementations are still free to support other
filesystems if they choose; it's just that fat was the lowest common
denominator and bios vendors never do any more than they absolutely have
to.  I've heard that macs can use hfs for the esp though.

> Parted is broken when it comes to btrfs, it doesn't handle it
> gracefully at all. See the screenshot: The top left corner shows
> that parted just defaults to MSDOS even though you can clearly see
> in the top right that there is no partition table written. The
> bottom terminal is the Ubuntu 14.10 Live USB stick for comparison.
> Commands used were sudo parted -l

Looking at your screen shots, it appears that there is something that at
least tries to look like it is an MBR there in the boot sector.  In
14.10, I fixed parted to correctly recognize filesystems on bare
devices, but had to take special steps to avoid confusing an ntfs/fat
boot sector for an MBR since they look very similar.  My guess is that
grub is trying to mimic an MBR and fooling parted into thinking that it
is one.  I probably just need to detect btrfs first and prefer that over
MBR like I did with fat and ntfs.

If you feel comfortable reinstalling grub ( and it sounds like you do ),
then you might conduct an experiment and zero out that first sector and
see if that fixes the problem, though obviously to boot you will then
need to reinstall grub.

> Should I bring this up with the parted developers as well?

You're talking to him ;)

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https://bugs.launchpad.net/bugs/1383948

Title:
  Ubiquity Installer doesn't recognize existing btrfs partitions

Status in “parted” package in Ubuntu:
  In Progress

Bug description:
  Steps to reproduce the bug:
  On a machine with an existing raw btrfs partition (no partition table, just raw btrfs to disk as btrfs is intended to be used)
  (created with sudo mkfs.btrfs /dev/sdc)
  From the 14.04.1 LTS live USB
  open a terminal
  scan for btrfs partitions using:
    sudo btrfs device scan
  then view the partition and data usage with
    sudo btrfs filesystem show
  The device is shown
  Label: none  uuid: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxxx
  	Total devices 1 FS bytes used 37.71GiB
  	devid    2 size 223.57GiB used 40.03GiB path /dev/sdc
  Start the Ubuntu Ubiquity Installer by clicking on the icon in the launcher
  Choose Download Updates and install Fluendo then
  Next
  Then choose Do Something Else, Choose partitions manually
  Scroll down to /dev/sdc
  The Ubiquity Partition manager doesn't recognize the btrfs disk/volume and just says free-space (see screenshot with proof)

  What should happen:
  At the partition screen it should recgonize my existing btrfs volume and let me reinstall without formating the btrfs volume

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