Re: Autoconfiguring root device and fstab(5) (wedges?)

[Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>]

On 26.03.2011 13:44, David Brownlee wrote:
> On Mar 26, 2011 11:58 AM, "Jean-Yves Migeon" 
> <jeanyves.migeon%free.fr@localhost>
> wrote:
>> I tried to use dkscan_bsdlabel(8) together with sysctl kern.root_device
>> very early during boot (/etc/rc.conf.d/fsck_root), however it returns
>> "Device busy", so I can't use it to circumvent the missing
>> DKWEDGE_METHOD_BSDLABEL options(4).
> 
> As an aside maybe there is some sense in a variation of
> DKWEDGE_METHOD_BSDLABEL which only configures a new bsdlabel partition type
> as wedge so help testing & migration...

(please note that I am not at all familiar with disklabel/mbr formats)

Shouldn't that be the opposite eg. push the creation of wedges forward
and propose some way to serialize that with the help of a disklabel/mbr
struct?

The two main issues I see with wedges is that:
- they are dynamically created. As we don't have some devfs-like tool
yet, it's hard to keep that information (eg. dkN, with N being
arbitrarily defined) across reboots, although I remember seeing a patch
that plays with wedge names.
- we have to support wedges during install step, or we will have the
functionality resting ~forever in kernel without much use (except for
>2TiB partitions and GPT users).

(wild guess) Is there some place reserved in disklabel (like "for future
use") we could tweak a bit so to tell the kernel "use wedges for
partitions found on this disk"?
While retaining compatibility with other BSDs, if possible.

-- 
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost