Re: [PATCH] UUID support

[Robert Millan]

On Fri, May 30, 2008 at 02:49:22AM +0800, Bean wrote:
> On Fri, May 30, 2008 at 2:17 AM, Robert Millan <address@hidden> wrote:
> > On Fri, May 30, 2008 at 12:50:42AM +0800, Bean wrote:
> >>
> >> BTW, I think we can embed the UUID of the root device in
> >> core.img/grub.elf, so that when the traditional root device fails to
> >> locate normal.mod, it uses the UUID to scan for root device.
> >
> > Good idea.  But I'd check for UUID first.  When you find a UUID match, it's
> > much more reliable than a filename one.
> 
> Here are some thought about how to store it. We can reuse the space
> occupied by prefix. Instead of one variable, we use zero-end strings
> like:
> 
> path=/boot/grub \0 uuid=xxx-xxx-xxxx \0 \0
> 
> We can also add other variable, for example, debug and default. debug
> is useful as it can show message before grub.cfg is loaded, and
> default is used to control the default menu entry. Other variable
> should be set in grub.cfg, as space is quite limited here.
> 
> path=/boot/grub \0 uuid=xxx-xxx-xxxx \0 debug=all \0 default=1 \0 \0
> 
> The space need to expand slightly, I guess something about 100 byte is
> more than enough. The whole block is prefixed by a magic number and
> block length, so that it's easy to locate by utility.
> 
> This also solve the savedefault issue, we can add a command like this:
> 
> save_env /path_to_core.img variable_name ..
> 
> It finds the magic number, and store the value of selected variable in
> the embedded environment block.

Then I suppose we could have a module that gets $uuid from environment and
searches for it to set $prefix?

Maybe we could search for everything else in the same module too, this way
we only have to iterate once.  It could check for things like:

  - filesystem uuid
  - partmap uuid (when we support it)
  - filename (based on user input via variable, rather than hardcoded
    normal.mod?)
  - filesystem label

-- 
Robert Millan

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