Name/label/id metadata: how do I make it go away

[Matt Churchyard]

>Warren/Freddie,

>Thank you for your replies.

>On 9/21/15 8:41 PM, Warren Block wrote:
>>> - gpt id
>>
>> A system-assigned ID in the GPT metadata.  Requires GPT partitioning.

>>> I have a zfs pool of "entire disks".  "zpool status" shows some 
>>> disks with their daX name (which I prefer) and some with a hideously 
>>> ugly name such as DISK-%20%20%20%20%20-WD-WMC4NOH1ASDF
>>
>> Disable those labels with kern.geom.label.gptid.enable="0" in 
>> /boot/loader.conf.

>Combining your two statements quoted above, I believe I can conclude that my ZFS "whole disk" drives must have some remnants of GPT left >over from their previous lives (namely the system-assigned ID in the GPT metadata).

>Surprisingly, these apparently GPT-supplied labels appear to "go away" 
>when I issue a "glabel stop".  I would not expect this given that Warren explained that glabels (whose metadata are stored at the end of the >device and completely outside the virtual device) are not the same as GPT labels (whose metadata are stored within the device on the GPT >metadata).

>I believe one of the following must be true:

>1. It is possible to use "glabel stop" to disable a "GPT system-assigned ID" -- even though glabel is a tool for manipulating another style of labels.

>2. "glabel stop" only affects glabels.  In my case my drives must contain "glables" and not "GPT system-assigned IDs" as Warren guessed.

>3. I misunderstood and glabels/GPS system-assigned IDs are really the same thing.

>Thank you again,

>Chris

>The diskid entries have nothing to do with GPT. I suspect your disks do not have any partitioning. These labels are generated automatically >based on the actual vendor supplied ID for each disk.

>The glabel command allows you to assign a label to a GEOM device, which will then appear as /dev/label/name. I personally dislike these as >they are not portable and are one block smaller than the original device, which is still accessible.

>It appears glabel is also responsible for identifying various other "labelling" methods that weren't necessary created using the utility. For >instance it will create /dev/ufsid/X devices, where X is the ID of a UFS filesystem it has found on a GEOM device. It also seems to be >responsible for creating /dev/gpt entries as well as /dev/diskid, which is possibly why they disappear when you run glabel stop. Most of this is >mentioned in the man page, although it doesn't mention the diskid entries; There does however appear to be a >geom/label/g_label_disk_ident.c source file >which implements the /dev/diskid/X functionality.

>The thing to be clear on is that although glabel is responsible for creating the device nodes for most of these labels, the way they are assigned is >very different 

>diskid - Automatic based on the ID of the disk - so should reference an entire disk gpt - Assigned manually to a partition by GPT partitioning a >disk and creating labelled partitions gptid - Automatic when you partition a disk with GPT and create partitions (every GPT partition has a unique >GUID) glabel - Assigned to any disk or partition manually by using the glabel command

>Interestingly, looking though sysctl, I see options to turn off most label devices, but nothing mentions diskid. I don't know if this is actually  >missing, or if one of the existing sysctls also turns them off. (Surely there should ideally be a kern.geom.label.diskid.enable?)

>kern.geom.label.ext2fs.enable: 1
>kern.geom.label.iso9660.enable: 1
>kern.geom.label.msdosfs.enable: 1
>kern.geom.label.ntfs.enable: 1
>kern.geom.label.reiserfs.enable: 1
>kern.geom.label.ufs.enable: 1
>kern.geom.label.ufsid.enable: 1
>kern.geom.label.gptid.enable: 1
>kern.geom.label.gpt.enable: 1

Ignore that last bit. Just found the sysctl to turn off the diskid entries -

kern.geom.label.disk_ident.enable: 1

Regards,
Matt Churchyard