A request for unnested UFS implementation in MBR

[Gary Palmer]

On Sun, Jul 08, 2018 at 11:02:30AM +0200, Ronald Klop wrote:
> On Sat, 07 Jul 2018 07:59:55 +0200, Manish Jain <jude.obscure at yandex.com>  
> wrote:
> 
> > 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.
> >
> > Thanks for reading this.
> > Manish Jain
> 
> Do you mean something like this? Gpart refuses to create a freebsd-ufs  
> partition in the MBR part.
> 
> # mdconfig -s 512m
> md0
> # gpart create -s MBR md0
> md0 created
> # gpart add -t freebsd-ufs -s 256m md0
> gpart: Invalid argument
> # gpart add -t freebsd-swap -s 256m md0
> gpart: Invalid argument
> 
> But you can create and newfs other types.
> 
> # gpart add -t linux-data -s 256M md0
> md0s1 added
> # newfs /dev/md0s1
> /dev/md0s1: 256.0MB (524288 sectors) block size 32768, fragment size 4096
> 	using 4 cylinder groups of 64.03MB, 2049 blks, 8320 inodes.
> super-block backups (for fsck_ffs -b #) at:
>   192, 131328, 262464, 393600
> 
> # gpart add -t freebsd md0
> md0s2 added
> # newfs /dev/md0s2
> /dev/md0s2: 256.0MB (524272 sectors) block size 32768, fragment size 4096
> 	using 4 cylinder groups of 64.00MB, 2048 blks, 8192 inodes.
> super-block backups (for fsck_ffs -b #) at:
>   192, 131264, 262336, 393408
> 
> 
> Interesting. I don't why this is.

freebsd-ufs, freebsd-swap, freebsd-zfs, etc, are GPT IDs.  freebsd
(without any suffix) is a MBR ID.  This is covered in the "gpart"
man page under each ID

Regards,

Gary