Subject: Re: Config ...
To: Matthew Jacob <mjacob@feral.com>
From: Eduardo E. Horvath <eeh@one-o.com>
List: tech-kern
Date: 08/21/1998 09:33:57
On Fri, 21 Aug 1998, Matthew Jacob wrote:
> The question is, what will you call the root disk in /etc/fstab? Will
> it be the globally unique name or the boot name? The boot name usually
> specifies how you were able to get to it from the boot prom. In OBP
> namespaces this is a device tree. In BIOS name spaces, it's the BIOS
> code (0x80 and above.). The global name, or the construction of it,
> may be a very expensive process timewise and subsystem wise. And anyway,
> you may want a root device separate from what you loaded the kernel
> from.
For consistency you would want to use whatever scheme you use to identify
the device when the system is running. That way your configuration
remains relatively static across H/W reconfigs. You would also want to
use this name for `boot -a'. (Whether you can do this is another issue.)
> > When would you create the device name?
>
> That's an open question (:-)). I think as late as possible- possibly
> not until open time and use a VFS to get to it.
The problem, of course is that you can't access the device until you
have a device node for it, and you need the device's name to generate the
node.
> Perhaps a cheezy little hack early in rc.single that builds system
> unique disk identifiers (based upon the hierarchy of WWN, VPD/Inquiry
> INFO, <other>, Disk Label Identifier) for all probed disks, and uses
> *that* to match (with aliases for ease of use) with entities in
> /etc/fstab. Or perhaps this could be a VFS mounted first with the
> kernel cons'ing up the names? Would this be an acceptable first
> pass?
You don't want to have to depend on anything to get into single-user mode.
In fact you don't want to have to even mount the root partition
read/write.
=========================================================================
Eduardo Horvath eeh@one-o.com
"I need to find a pithy new quote." -- me