Re: [PATCH] init: add root=PARTUUID=UUID+/-%d support

From: Kay Sievers
Date: Thu Jun 02 2011 - 08:50:08 EST

On Wed, Jun 1, 2011 at 21:49, Will Drewry <wad@xxxxxxxxxxxx> wrote:
> Not sure if this is practical and/or interesting to others, but it's a
> minimal change --
> Expands root=PARTUUID=UUID syntax to support selecting a root partition
> by integer offset from a known, unique partition. ÂThis approach
> provides similar properties to specifying a device and partition number,
> but using the UUID as the unique path prior to evaluating the offset.
> For example,
> Âroot=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B+1
> selects the partition with UUID 99DE.. then select the next
> partition.
> This change is motivated by a particular usecase in Chromium OS where
> the bootloader can easily determine what partition it is on (by UUID)
> but doesn't perform general partition table walking.
> That said, support for this approach provides a direct mechanism for the
> user to modify the root partition to boot without specifically needing
> to extract each PARTUUID or update the bootloader explicitly when the
> root partition UUID is changed (if it is recreated to be larger, for
> instance, restored, etc). ÂPinning to a /boot partition UUID with an
> offset allows the arbitrary root partition reconfiguration/modifications
> with slightly less ambiguity than just [dev][partition] and less
> stringency than the specific root partition UUID.

Kind of a creative notation to add/substract something from a uuid. :)

If we are not sure we'll not need another magic thing in the future,
we might want to go for a named parameter to add?
Maybe instead of:
we could do:

Might be it's a but over the top, but the key is named PARTUUID, and a
+- to it doesn't seem to explain what it does and can not really be
expanded for even more creative uses. :)

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