[ubuntu-cloud] Cloud-images: Announcing UEFI and BIOS/GPT images for Trusty

Ben Howard ben.howard at canonical.com
Mon Dec 9 21:22:41 UTC 2013

Starting with Ubuntu 14.04 LTS, the Cloud Images for AMD64 will include
a new UEFI disk image. This new image has been designed to be as
flexiable as possible, supporting not only UEFI, but BIOS/GPT (current
images are BIOS/MBR) and support for P{V,Y}GRUB's w/ GPT support. As a
result, these new images should work on a variety of hypervisor
platforms. The daily image will be available at [1] once they exit the
build system within the next several hours.

The following output show the layout of the disk:

    ubuntu at gpt-test:~$ sudo parted /dev/vda -- print
    Model: Virtio Block Device (virtblk)
    Disk /dev/vda: 10.7GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt

    Number  Start   End     Size    File system  Name                 Flags
    127     1049kB  2097kB  1049kB               BIOS boot partition  bios_grub
    128     2097kB  89.1MB  87.0MB  fat32        EFI System           boot
     1      89.1MB  10.7GB  10.6GB  ext4         Linux filesystem

The layout is explained as followed:
* Partition 127 is for BIOS/GPT booting
   * This partition is not mounted.
* Partition 128 is used for the UEFI installation. It is mounted to
   * GRUB UEFI is configured to look at partition 1's /boot/grub/grub.cfg
   * UEFI is configured as a removal disk
   * In order to register the disk in the hypervisor's NVRAM, you'll
need to run
      grub-install again.
* Partition 1 is maintained as the traditional 'cloudimg-rootfs'
   * /boot/grub/menu.lst will be maintained for P{V,Y}GRUB.

Note: due to a kernel bug [2], when these images are booted with the
root disk using a virtio device, /dev/vda{127,128} device nodes are not
created. Therefore, for the time being, you will need to use a
non-virtio device in order for these images to boot properly.


[2] https://bugs.launchpad.net/bugs/1258631


Ben Howard
ben.howard at canonical.com
GPG ID 0x5406A866

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