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

[Phillip Susi]

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On 10/28/2014 09:39 PM, Damiön la Bagh wrote:
> BTRFS reserves the first 64Kib in order to allow booting. GRUB2 
> already supports booting from BTRFS. As BTRFS is its own partition 
> table, LVM and filesystem in one.

Last I saw, when adding the btrfs module to the grub core, it grew
larger than 64k and so wouldn't fit in that reserved space, but if you
say it is working that's neat.

> Partition tables are legacy from the 50's!! it's 2014! Technology
> has gotten past partition tables in both ZFS and BTRFS.

ZFS and BTRFS have nothing to do with it.  If you want to, you can
format an entire disk as ext4 or any other fs too; it just isn't smart.
With btrfs on the disk without a partition table, it becomes impossible
to share that disk with an OS that does not understand btrfs, even by
using eg. gparted to repartition the drive and add a small shared
partition.  We also have a new partition table format in the last few
years that newer computers require to boot since the bios is finally
going away.  Even if you can manage to get a bios based computer to boot
directly from a full btrfs volume ( and many bios implementations won't
boot the disk unless they recognize a valid dos partition table with an
active partition ), this won't fly with UEFI.

> It's not about the 1mb that a partition table occupies but
> removing complexity and overhead (layers of the onionskin). This
> leads to a speed increase in btrfs especially on SSD's. Plus it's
> easier to manage storage when you have One common set of commands
> instead of several unrelated programs each with their own syntax.
> So in the end it's also faster to set up your system and manage it
> running raw btrfs.

There is no overhead to placing a filesystem on a partition instead of
the raw device.  Formatting the raw device does not make it one iota
faster.

> Swap and that terrible EFI folder can be held on a SD card to 
> counter any argument before it starts.

Assuming the computer has one and that it's UEFI firmware recognizes it.

Some other scenarios that come to mind where you will regret not having
a partition table are if you ever add a second disk and want to expand
btrfs to span or raid across them both.  I'm pretty sure the grub btrfs
code does not handle this so you would need to add a /boot partition.
Another is that if that disk is ever plugged into a Windows system, it
will helpfully offer to format the "blank" disk instead of recognizing
that it is occupied by another OS.  A partition table is pretty cheap
insurance against this.

> Yes it still happens in 14.10 please see screenshots with proof.

Ok, can you post the output of parted -l?  Does it recognize that it
is btrfs?
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https://bugs.launchpad.net/bugs/1383948

Title:
  Ubiquity Installer doesn't recognize existing btrfs partitions

Status in “ubiquity” package in Ubuntu:
  Incomplete

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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