switching to DUIDs (and back)

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switching to DUIDs (and back)

alan01346
I thought this was documented somewhere but I'm not finding it in Googling.

I don't really like DUIDs, but I want to stick in a second drive
controller temporarily to recover data off some old hard drives.
Which means /dev/wd0a etc is going to change since the added
controller (in a PCI slot) becomes primary.  I'm perfectly comfortable
manually mounting and unmounting the old drives, I don't want to add
them to an fstab.

I want to replace my fstab with one that accesses my current
partitions using DUIDs.  Disklabel shows me a DUID for the drive, how
do I set up individual partitions?  Or is there already a DUID (or
UUID) for each partition that I need to find and use?

The main thing right now is to change fstab so it boots back up
smoothly with DUIDs.  I'll comment out my current entries and put the
DUID ones below.  And yes, I already made a backup copy.  All IDE,
can't afford SCSI.

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Re: switching to DUIDs (and back)

Josh Grosse-3
On Sun, Oct 29, 2017 at 11:25:22AM -0400, Alan Corey wrote:

> I thought this was documented somewhere but I'm not finding it in Googling.
>
> I don't really like DUIDs, but I want to stick in a second drive
> controller temporarily to recover data off some old hard drives.
> Which means /dev/wd0a etc is going to change since the added
> controller (in a PCI slot) becomes primary.  I'm perfectly comfortable
> manually mounting and unmounting the old drives, I don't want to add
> them to an fstab.
>
> I want to replace my fstab with one that accesses my current
> partitions using DUIDs.  Disklabel shows me a DUID for the drive, how
> do I set up individual partitions?  Or is there already a DUID (or
> UUID) for each partition that I need to find and use?
>
> The main thing right now is to change fstab so it boots back up
> smoothly with DUIDs.  I'll comment out my current entries and put the
> DUID ones below.  And yes, I already made a backup copy.  All IDE,
> can't afford SCSI.

The fstab(5) man page is your friend. There's even an EXAMPLES section
in there for you to review that shows how DUIDs are addressed.

Basically, replace "wd0" with the drive's DUID.

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Re: switching to DUIDs (and back)

Josh Grosse-3
On Sun, Oct 29, 2017 at 11:30:51AM -0400, Josh Grosse wrote:
> Basically, replace "wd0" with the drive's DUID.

I'm wrong, of course.  Replace "/dev/wd0" with the drive's DUID,
then append "." followed by the partition.

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Re: switching to DUIDs (and back)

alan01346
In reply to this post by alan01346
>On Sun, Oct 29, 2017 at 11:30:51AM -0400, Josh Grosse wrote:
>> Basically, replace "wd0" with the drive's DUID.

>I'm wrong, of course.  Replace "/dev/wd0" with the drive's DUID,
>then append "." followed by the partition.

Thank you, I was thinking every partition has a UUID and I needed to
find and use those.  But even in Linux it's apparently only devices
that have UUIDs.  They're almost like DOS/Windows drive serial
numbers, but those are generated when you format a partition and only
apply to the partition.  Yes, I was looking at man pages but what I
was looking for doesn't exist.

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Re: switching to DUIDs (and back)

Josh Grosse-3
On 2017-11-01 10:08, Alan Corey wrote:

> Thank you, I was thinking every partition has a UUID and I needed to
> find and use those.  But even in Linux it's apparently only devices
> that have UUIDs.  They're almost like DOS/Windows drive serial
> numbers, but those are generated when you format a partition and only
> apply to the partition.  Yes, I was looking at man pages but what I
> was looking for doesn't exist.

I'm sorry.  Originally, you wrote:

> I want to replace my fstab with one that accesses my current
> partitions using DUIDs.  Disklabel shows me a DUID for the drive, how
> do I set up individual partitions?  Or is there already a DUID (or
> UUID) for each partition that I need to find and use?

A DUID is per drive, and is reported to you by disklabel(8).

     # disklabel wd0 | grep duid

You can change the DUID value as well, if you desire to.
See the "i" command in the disklabel editor section of the
man page.

You'd also written ...

> I don't really like DUIDs ...

They were introduced specifically to eliminate needing to
edit fstab(5)entries in the event of device number changes.