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Old 04-21-2008, 02:37 PM
"Anthony E. Caudel"
 
Default OT: Question UUID

I have noticed in some distros (namely Ubuntu) that the fstab uses
UUID's rather than /dev references. Is this a better way?


Does it eliminate the problem of /dev references changing when another
drive, i.e., an external USB drive, is plugged in? The /dev references
may change but the UUID's in fstab wouldn't, would they?


Tony

--
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.
-- Benjamin Franklin

--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-21-2008, 03:41 PM
"Dirk Heinrichs"
 
Default OT: Question UUID

Am Montag, den 21.04.2008, 16:37 +0200 schrieb Anthony E. Caudel:
> I have noticed in some distros (namely Ubuntu) that the fstab uses
> UUID's rather than /dev references. Is this a better way?

Yes.

> Does it eliminate the problem of /dev references changing when another
> drive, i.e., an external USB drive, is plugged in?

Yes.

> The /dev references
> may change but the UUID's in fstab wouldn't, would they?

Correct.

The other possible way would be to give your devices unique names,
either via udev or by using LVM. Advantage over UUIDs: much easier to
read.

Bye...

Dirk
 
Old 04-21-2008, 05:27 PM
Michael Schmarck
 
Default OT: Question UUID

Anthony E. Caudel <tony.caudel@sbcglobal.net>:

> I have noticed in some distros (namely Ubuntu) that the fstab uses
> UUID's rather than /dev references. Is this a better way?
>
> Does it eliminate the problem of /dev references changing when another
> drive, i.e., an external USB drive, is plugged in? The /dev references
> may change but the UUID's in fstab wouldn't, would they?

Correct. UUIDs are universally unique (as the name already "suggests" *g*)
and thus, there cannot be a clash.

Michael Schmarck
--
Every journalist has a novel in him, which is an excellent place for it.


--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-21-2008, 05:29 PM
Michael Schmarck
 
Default OT: Question UUID

Dirk Heinrichs <dirk.heinrichs@online.de>:

> Am Montag, den 21.04.2008, 16:37 +0200 schrieb Anthony E. Caudel:
>> I have noticed in some distros (namely Ubuntu) that the fstab uses
>> UUID's rather than /dev references. Is this a better way?
>
> Yes.
>
>> Does it eliminate the problem of /dev references changing when another
>> drive, i.e., an external USB drive, is plugged in?
>
> Yes.
>
>> The /dev references
>> may change but the UUID's in fstab wouldn't, would they?
>
> Correct.
>
> The other possible way would be to give your devices unique names,
> either via udev or by using LVM. Advantage over UUIDs: much easier to
> read.

Disadvantage: Not guaranteed to be unique. It could, theoretically
at least, happen that there are two devices with the same names.
The same disadvantage exists, if you use filesystem labels.

Advantage of fs labels: No need for another layer like LVM.

Michael Schmarck
--
i dont even know if it makes sense at all This is an experimental patch
for an experimental kernel )
-- Ingo Molnar on linux-kernel


--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-21-2008, 08:36 PM
Roy Wright
 
Default OT: Question UUID

Michael Schmarck wrote:
> Correct. UUIDs are universally unique (as the name already "suggests" *g*)
> and thus, there cannot be a clash.

Not quite true, drives in a RAID have the same UUID.
Here's my raid5 for an xxample:

# blkid | grep mdraid
/dev/sdb1: UUID="bf59d132-8b98-7d9c-c526-af1cfb835fa3" TYPE="mdraid"
/dev/sdc1: UUID="bf59d132-8b98-7d9c-c526-af1cfb835fa3" TYPE="mdraid"
/dev/sdd1: UUID="bf59d132-8b98-7d9c-c526-af1cfb835fa3" TYPE="mdraid"

So you would need to reset the UUID before reusing a drive from an array.

Have fun,
Roy
--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-21-2008, 09:22 PM
Neil Bothwick
 
Default OT: Question UUID

On Mon, 21 Apr 2008 17:41:58 +0200, Dirk Heinrichs wrote:

> The other possible way would be to give your devices unique names,
> either via udev or by using LVM. Advantage over UUIDs: much easier to
> read.

Or you could use filesystem labels.


--
Neil Bothwick

Electricians DO IT until it Hz...
 
Old 04-21-2008, 10:14 PM
"Mark Knecht"
 
Default OT: Question UUID

On Mon, Apr 21, 2008 at 2:22 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Mon, 21 Apr 2008 17:41:58 +0200, Dirk Heinrichs wrote:
>
> > The other possible way would be to give your devices unique names,
> > either via udev or by using LVM. Advantage over UUIDs: much easier to
> > read.
>
> Or you could use filesystem labels.
>
I've used filesystem labels for a long time and generally it works
really well. Only problem I've had is my Dad's machine has a Maxtor
1-touch 1394 drive. It seems that often it doesn't get recognized by
the 1394 subsystem fast enough to satisfy whatever requirements the
Gentoo scripts have for the label being readable so it doesn't
reliably get recognized every time.

Cheers,
Mark
--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-21-2008, 11:59 PM
"Anthony E. Caudel"
 
Default OT: Question UUID

Michael Schmarck wrote:

Anthony E. Caudel <tony.caudel@sbcglobal.net>:


I have noticed in some distros (namely Ubuntu) that the fstab uses
UUID's rather than /dev references. Is this a better way?


Does it eliminate the problem of /dev references changing when another
drive, i.e., an external USB drive, is plugged in? The /dev references
may change but the UUID's in fstab wouldn't, would they?



Correct. UUIDs are universally unique (as the name already "suggests" *g*)
and thus, there cannot be a clash.

Michael Schmarck

Any chance that GRUB will ever use these? I have a sata hd carrier and
when I reboot with it plugged in, grub sees the disk order differently
and gives me problems (I either have to get a grub command line and boot
manually or use a Grub boot floppy).


Tony

--
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.
-- Benjamin Franklin

--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-22-2008, 09:43 PM
Mick
 
Default OT: Question UUID

On Monday 21 April 2008, Mark Knecht wrote:
> On Mon, Apr 21, 2008 at 2:22 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> > On Mon, 21 Apr 2008 17:41:58 +0200, Dirk Heinrichs wrote:
> > > The other possible way would be to give your devices unique names,
> > > either via udev or by using LVM. Advantage over UUIDs: much easier to
> > > read.
> >
> > Or you could use filesystem labels.
>
> I've used filesystem labels for a long time and generally it works
> really well. Only problem I've had is my Dad's machine has a Maxtor
> 1-touch 1394 drive. It seems that often it doesn't get recognized by
> the 1394 subsystem fast enough to satisfy whatever requirements the
> Gentoo scripts have for the label being readable so it doesn't
> reliably get recognized every time.

I have thought about using labels, but never really ventured into it (I think
I tried it once on a server). Can I do it retrospectively on ext2, reiserfs
and xfs, or is it going to erase the contents of the partition?
--
Regards,
Mick
 
Old 04-22-2008, 10:17 PM
Neil Bothwick
 
Default OT: Question UUID

On Tue, 22 Apr 2008 22:43:12 +0100, Mick wrote:

> I have thought about using labels, but never really ventured into it (I
> think I tried it once on a server). Can I do it retrospectively on
> ext2, reiserfs and xfs, or is it going to erase the contents of the
> partition?

You can, see the man pages for the various filesystem tools, e.g.

tune2fs -L ROOT /dev/sda5


--
Neil Bothwick

Why is the word abbreviation so long?
 

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