Date: Tue, 22 Sep 2015 07:50:51 -0700 From: Freddie Cash <fjwcash@gmail.com> To: Matt Churchyard <matt.churchyard@userve.net> Cc: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: Name/label/id metadata: how do I make it go away Message-ID: <CAOjFWZ59y8w2PUs11wH2R=NBSJX6hNiFaBJv7gpfQPYBv%2BkO5w@mail.gmail.com> In-Reply-To: <5cd22ba8f67a46a0a1f77b4646f3eaa5@SERVER.ad.usd-group.com> References: <56004C68.4020904@stankevitz.com> <alpine.BSF.2.20.1509212126470.4544@wonkity.com> <5600F0DF.8000805@stankevitz.com> <e1abb521ab324532b3445d26984f5638@SERVER.ad.usd-group.com> <5cd22ba8f67a46a0a1f77b4646f3eaa5@SERVER.ad.usd-group.com>
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On Tue, Sep 22, 2015 at 2:44 AM, Matt Churchyard via freebsd-fs < freebsd-fs@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=3D"0" in > >> /boot/loader.conf. > > >Combining your two statements quoted above, I believe I can conclude tha= t > 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 >devi= ce > 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 contai= n > "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 >base= d > 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, whic= h > 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 >responsibl= e > for creating /dev/gpt entries as well as /dev/diskid, which is possibly w= hy > they disappear when you run glabel stop. Most of this is >mentioned in th= e > 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 >whic= h > 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 partiti= on > 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 entrie= s > - > > kern.geom.label.disk_ident.enable: 1 > =E2=80=8BThat 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? --=20 Freddie Cash fjwcash@gmail.com
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