FYI: ROOTUUID= and initrd-less kernel

[Tim Gardner]

On 02/02/2012 02:53 AM, Paolo Pisati wrote:
> Yesterday i played a bit with this parameter and made it work: the
> kernel is already good, all it takes to convert a running ubuntu
> installation to use ROOTUUID is a conversion of the MBR to a GPT (it
> seems the geometry we picked is a bit unfortunate so manual
> intervention in needed to accomodate the second partition) and then
> the creation of an hybrid MBR to expose the first partition (the vfat
> one, containing the bootloaders) to the on-board boot room. Some
> details about this conversion could be found here: [1]
>
> After that, it's just a matter of changing the boot parameters:
>
> mmcinfo setenv bootargs ro elevator=noop vram=12M
> omapfb.mode=dvi:1280x720MR-16 at 60 mpurate=auto
> root=PARTUUID=A2375B29-39D4-40CA-9304-A80132786DBC fixrtc
> console=tty0 console=ttyO2,115200n8 rootwait fatload mmc 0:1
> 0x80000000 uImage bootm 0x80000000
>
> (notice there's no "fatload mmc 0:1 0x8XXXXXXXXX uInitrd")
>
> Here is a boot log [2] of my beaglexm with this method.
>
> And here [3] is how the GPT/MBR looks like after the conversion.
>
> For new installation this could be a solution, but i don't know how
> feasible is an automatic conversion of old installation.
>
> 1: http://linux.bplaced.net/#gpt-mit-hybridem-mbr 2:
> http://pastebin.ubuntu.com/826155/ 3:
> http://paste.ubuntu.com/826166/

Well, thats just pretty dang cool.

Oliver, Steve - it appears that support for partition UUIDs is already 
in the kernel. While this may not be the ideal solution for initrd-less 
x86, how about for new ARM installs ?

rtg
-- 
Tim Gardner tim.gardner at canonical.com