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

[Freddie Cash]

On Tue, Sep 22, 2015 at 2:44 AM, Matt Churchyard via freebsd-fs <
freebsd-fs at freebsd.org> wrote:

> >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
>

​That must be new in 10.x.

In 9.x (and presumably 8.x), the gptid sysctl disables the diskid labels.
Guessing in 10.x they split the two into separate sysctls?

-- 
Freddie Cash
fjwcash at gmail.com