Re: Unique Identifier for Disk
Re: Unique Identifier for Disk
- Subject: Re: Unique Identifier for Disk
- From: Jeffrey Berman <email@hidden>
- Date: Wed, 28 Apr 2004 08:51:36 -0500
On 4/27/04 3:59 AM, Michael Ziober <email@hidden> wrote:
>
On Mon, 26 Apr 2004 22:15:20 -0500, Jeffrey Berman
>
<email@hidden> wrote:
>
>
> One could get the disk name associated with "disk0s10" (and eliminate
>
> the
>
> grep pipe) using the following:
>
>
>
> df | awk -F/ '/disk0s10/ {print $5}'
>
>
>
> However, getting the disk name this way is not of much use unless the
>
> associated device file name in the /dev directory is unique across
>
> restarts.
>
>
>
> Does anyone know if this is the case?
>
>
>
> -Jeffrey Berman
>
>
No, the device entry is not guaranteed to be the same across restarts.
>
Internal drives (other than the startup drive) may spin up and be
>
identified in a non-deterministic order. Removable media (flash memory
>
devices, optical discs, etc.) may be present or absent. External
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devices (FireWire and USB drives) may be powered up or not. After boot,
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devices may be unmounted and remounted in a different order (Disk
>
Utility). Disk images may be mounted and unmounted. All the while
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device identifiers are being dynamically assigned and revoked.
>
>
But HFS formatted hard drives are assigned a unique identifier when
>
they are formatted.
So are the device file names associated with HFS-formatted drive partitions
unique across restarts? Or is this "unique identifier" located elsewhere?
>
For example, the following bash pipeline displays
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the unique identifier and mount point for all locally mounted volumes:
>
>
df -t hfs | tail +2 | sed -e 's|^/dev/||' | while read d b u a c m; do
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x=$(/System/Library/Filesystems/hfs.fs/hfs.util -k "$d"); echo "$x $m";
>
done
At least on my machine, this code returns the volume mount points but not
any "unique identifier" values.
-Jeffrey Berman
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