A request for unnested UFS implementation in MBR

[Andrey V. Elsukov]

On 07.07.2018 08:59, Manish Jain wrote:
> 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.

The main goal of using bsdlabel was the boot code, I think.
MBR has less than 512 bytes to keep boot code. This is too little to be
able place the code that can read UFS filesystem to read and start loader.

I'm not sure, but AFAIR there were some hacks in the boot code, that
allowed to read from the raw partition as fallback.
I.e. you can try to create MBR with "freebsd" slice, make filesystem
with newfs on this slice and write boot1 bootcode to this slice at
proper offset using dd(1). But as I said, I'm not sure. There were many
changes in this area and I did not followed by them.

-- 
WBR, Andrey V. Elsukov

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