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From: Roger Heflin <rogerheflin@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] logical volume usage type code, equivalent to GPT partition type GUID
Date: Wed, 3 Nov 2021 13:21:27 -0500	[thread overview]
Message-ID: <CAAMCDed2KFtOawdC-kZ6NUsryurYbN6ZHSmXAMEr9bymP9TpZw@mail.gmail.com> (raw)
In-Reply-To: <CAJCQCtRCEtGmsVQt0ug4c6PxGXkwhHjtrppNPSxa0StYs08mQA@mail.gmail.com>

You have some basic problems.

#1 with shared lvm you would need a way to tell where it should go, so
you would have to have a mount_hostname type data in logical_volumes
sections.

#2 you would also need a mount_point entry, and a mount_opts entry.

And then at the end you are basically moving fstab into the
logicial_volume headers and that is not that useful overall because it
does not simplify anything for the most part, and probably actually
complicates things as the hostname change would get tricky, and/or
mountpoint changes would require lvm commands (harder than editing
fstab).

So long as the lv's are named reasonably then someone who knows they
are doing can mount up/recreate fstab with the lv in the right place
(say var_log_abrt would mount on /var/log/abrt).

I am not sure this simplifies anything nor improves anything except in
the case of a lost fstab, but naming the lv's verbosely at least makes
that easier.

On Wed, Nov 3, 2021 at 12:45 PM Chris Murphy <lists@colorremedies.com> wrote:
>
> Hi,
>
> I'm wondering to what degree the current LVM metadata format(s) can
> support additional or even arbitrary metadata.
>
> The UEFI spec defines the GPT, and GPT defines a "partition type GUID"
> for each partition to define it's usage/purpose, in rather open ended
> fashion. I'm wondering about an equivalent for this with LVM, whether
> it's useful and how difficult it would be to implement. This is all
> very hypothetical right now, so a high level discussion is preferred.
>
> The starting point is the Discoverable Partitions Spec:
> http://systemd.io/DISCOVERABLE_PARTITIONS/
>
> Where GPT partition type codes are used to discover file systems, and
> their intended use without having to explicitly place them into
> /etc/fstab for startup time discovery and mounting. But LVM doesn't
> have an equivalent for exposing such a capability, because it implies
> many volumes within the larger pool and also the pool might comprise
> many devices.
>
> The same problem exists for Btrfs subvolumes, and ZFS datasets.
>
> What might be possible and what is definitely not possible, is what
> I'm interested in understanding for now.
>
> Thanks,
>
> --
> Chris Murphy
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://listman.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

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  reply	other threads:[~2021-11-03 18:22 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-03 17:44 Chris Murphy
2021-11-03 18:21 ` Roger Heflin [this message]
2021-11-03 20:15 ` David Teigland

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