Fwd: A request for unnested UFS implementation in MBR

CyberLeo cyberleo at cyberleo.net
Sun Jul 8 02:34:31 UTC 2018

On 07/07/2018 03:50 PM, Manish Jain wrote:
> Hi,
> I made a request for FreeBSD UFS filesystem to the freebsd-fs list. Just
> for opinions on this list, I am forwarding that request underneath.
> Tx
> Manish Jain
> -------- Forwarded Message --------
> Subject: A request for unnested UFS implementation in MBR
> Date: Sat, 7 Jul 2018 11:29:55 +0530
> From: Manish Jain <jude.obscure at yandex.com>
> To: freebsd-fs at freebsd.org
> Hi all,
> I am a longtime user of FreeBSD, which now serves as my only OS.
> There is one request I wished to make for FreeBSD filesystems. While UFS
> implementation under GPT is unnested just as Ext2, the MBR
> implementation of UFS continues to piggyback on an unnecessary nest (in
> a BSD slice).
> Can it not be considered as an alternative to provide a UFS partition
> (unnested) under MBR too ?
> Existing users could continue to use the freebsd::freebsd-ufs scheme,
> while fresh usage could have the alternative of UFS directly recorded in
> the MBR.
> I should perhaps note that unlike most users who have shifted to GPT of
> late, I much prefer MBR because 1) the scheme's design by itself keeps
> the number of slices/partitions in a disk manageable; and 2) I can use
> the boot0 manager, my favourite boot manager.

You can create a UFS filesystem on any disk device, including an
unlabeled slice of any type code, right now. This might even be safe if
you never run any OS that might misinterpret the type codes you have
used! Simply create your desired layout with your chosen type codes, and
run newfs on the appropriate device node. The FreeBSD kernel does not
care about type codes when mounting filesystems enumerated in the fstab
or via device nodes provided manually.

However, you cannot boot FreeBSD using the native bootstrap without GPT
or a BSD label on your boot device, as MBR offers no designated place to
put the second stage bootstrap.

Hope this helps!

Fuzzy love,

<CyberLeo at CyberLeo.Net>
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