A request for unnested UFS implementation in MBR

[Gary Palmer]

On Mon, Jul 09, 2018 at 03:05:35AM +0530, Manish Jain wrote:
> On 07/08/18 14:32, 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
> 
> Hi all,
> 
> I will reply to all the answers (which accumulated as I had a very nice
> long sleep, thank you) to this thread here.
> 
> This is what I get currently applying gpart to my USB pen drive:
> 
> /root <<: gpart create -s MBR da0
> da0 created
> /root <<: gpart add -t linux-data -s 1G da0
> da0s1 added
> /root <<: gpart add -t freebsd-ufs -s 1G da0
> gpart: Invalid argument # WHY ?

Hi,

As I said in my email, freebsd-ufs is a GPT ID.  MBR has a very
restricted set of what is considered valid - from memory it's a single
byte.  That means freebsd-swap, freebsd-zfs, freebsd-ufs, etc aren't
valid.

> It currently is a real bother having to create UFS, with a whole lot of
> extra commands:
> 
> /root <<: gpart add -t freebsd -s 1G da0
> da0s2 added
> /root <<: gpart create -s BSD da0s2
> da0s2 created
> /root <<: gpart add -t freebsd-ufs da0s2
> da0s2a added

There is nothing forcing you to create the BSD label

# mdconfig -s 512m
md0
# gpart create -s MBR md0
md0 created
# gpart add -t freebsd md0
md0s1 added
# newfs /dev/md0s1
/dev/md0s1: 512.0MB (1048560 sectors) block size 32768, fragment size 4096
        using 4 cylinder groups of 128.00MB, 4096 blks, 16384 inodes.
super-block backups (for fsck_ffs -b #) at:
 192, 262336, 524480, 786624
# mount /dev/md0s1 /mnt
# 

> The extra commands mean that when a user wants to quickly put a
> partition on a disk of any kind, it is much easier using Ext2.
> 
> If the original command (highlighted with WHY ?) could succeed as such
> (or perhaps with a slight alteration: gpart add -t ufs -s 1G da0), UFS
> becomes as convenient as Ext2 for general purpose usage.
> 
> There is another way to think about the situation.
> 
> FreeBSD currently caters to only 2 types of users:
> 
> 1) Dedicated disk users - use BSD schema
> 
> 2) Slice users - use MBR schema + BSD schema
> 
> With very little effort, we can make the OS cater to the third kind of
> users : partition users (use MBR + EBR - no BSD). This makes FreeBSD
> behaviour same as what other operating systems do - expect the user to
> use one of the 3 primary partitions for /, and any extra filesystems
> (/usr or /var or swap) optionally needed to be found in the EBR.

I do not understand why you need to create the BSD label.  Nothing
in the GEOM framework is forcing you to do that

Is this for a bootable disk or just storage?

Regards,

Gary