[Linux-ia64] GUID filesystem+device identification ?

[Linux-ia64] GUID filesystem+device identification ?

[Martin Wilck]

Hi all,

Has anybody yet thought about the possibility to use
a mechanism like devfs for identifying devices and file systems
by their GUID? This would be a major improvement over Linux's current
approach of identifying devices, particularly disk drives.

In principle, it would be possible to change controllers and
disks arbitrarily and still maintain a valid file system in which
all devices and sub-file systems would be identified by ther GUIDs
(think of the device in fstab specified by GUID instead of /dev/sda3
or whatever).

I think something like this could well coexist with devfs in its current
implementation, e.g. by a collection of softlinks , something like

/dev/guid/disk/[DISK_GUID]->/dev/scsi/host1/bus0/target2/lun0
/dev/guid/partitions/[PARTITION_GUID]->(you guess).

where these links would be auto-generated when a driver encounters
a disk and and the partition table is analyzed.

Links for other devices could of course also exist in /dev/guid,
although I think disks and parttions give most benefit.

The approach above would allow entries like

/dev/[PARTITION_GUID] /usr ext2 defaults 2 1

in fstab, so no need to change fstab if controllers or disks
are added/removed in a system.

Unlike the "filesystem label" approach, this would work with any
filesystem type, and even for entire disks and other devices.

Is anybody working on something like this, or does it even exist
already?
If no, what is your opinion on its usefulness?

Regards,
Martin

-- 
Martin Wilck     <Martin.Wilck@fujitsu-siemens.com>
FSC EP PS DS1, Paderborn      Tel. +49 5251 8 15113

Re: [Linux-ia64] GUID filesystem+device identification ?

[Christoph Hellwig]

On Fri, May 18, 2001 at 06:50:44PM +0200, Martin Wilck wrote:
> 
> Hi all,
> 
> Has anybody yet thought about the possibility to use
> a mechanism like devfs for identifying devices and file systems
> by their GUID? This would be a major improvement over Linux's current
> approach of identifying devices, particularly disk drives.
> 
> In principle, it would be possible to change controllers and
> disks arbitrarily and still maintain a valid file system in which
> all devices and sub-file systems would be identified by ther GUIDs
> (think of the device in fstab specified by GUID instead of /dev/sda3
> or whatever).

I think support for GUID=foo in /etc/fstab for mount would be pretty easy.
Having it in ther kernel would be nicer and shouldn't be that difficult,
on the other hand it'll need a consensus on wether the kernel should look
at every partition on startup - IIRC some people where opposed to such
soloutions in the past.

	Christoph
-- 
Of course it doesn't work. We've performed a software upgrade.

Re: [Linux-ia64] GUID filesystem+device identification ?

[Martin Wilck]

> Having it in ther kernel would be nicer and shouldn't be that difficult,
> on the other hand it'll need a consensus on wether the kernel should look
> at every partition on startup - IIRC some people where opposed to such
> soloutions in the past.
>

The kernel looks at partition type GUID of all partitions already
(in fs/partitions/efi.c), all it would need to do apart from that
look at the Unique GUID as well and create a GUID->device
table somewhere.

Cheers, Martin

-- 
Martin Wilck     <Martin.Wilck@fujitsu-siemens.com>
FSC EP PS DS1, Paderborn      Tel. +49 5251 8 15113