Subject: Re: wedges and what does that mean?
To: David Laight <>
From: Jason Thorpe <>
List: current-users
Date: 09/27/2006 16:01:04
On Sep 4, 2006, at 12:49 PM, David Laight wrote:

> On Mon, Sep 04, 2006 at 01:34:39PM +0200, Martin Husemann wrote:
>> But wedges have no inherent corelation to some on-disk partition  
>> format,
>> like the disklabel which the old partition code used.
> Unfortunately this sucks realtime....
> There is nothing (to my knowledge) to ensure that the 'wedge numbers'
> stay anything like consistent across reboots.
> So add a 'partition' to an MBR disk, and when you reboot all the  
> numbers
> will change.

...and this is different from USB (or Firewire or FibreChannel) how?

We already have this problem, wedges doesn't really make it any  
worse.  So we will address the problem in a way that works for  
everything.  Some ideas:

- Persistent volume identifiers that you can use to specify the volume  
to mount (because you REALLY care about the volume, not the device it  
happens to be on at the moment, right?)

- A devfs implementation whereby the wedge code can construct symbolic  
links to the /dev/dkN entries based on volume or partition naming  
information (constructed perhaps from the 4.4BSD "pack label" +  
partition letter or maybe the GPT "partition name").

> I'm also not at all sure how the boot code is meant to locate the  
> correct
> root filesystem.

that's easy -- and it already exists in the kernel.

-- thorpej