From: james.harris.1@gmail.com   
      
   On 31/12/2021 09:37, Rod Pemberton wrote:   
   > On Fri, 31 Dec 2021 04:22:24 -0500   
   > Rod Pemberton  wrote:   
   >   
   >> On Mon, 20 Dec 2021 16:17:40 +0000   
   >> James Harris  wrote:   
   >   
   >>> So far I have a VBR which reads through the root dir, finds the   
   >>> target file, and loads its first sector.   
   >>   
   >> Why wouldn't you require that the file always be the first entry in   
   >> the root dir? ...  That conserves space for more code, right? ...   
      
   Well, what's best, to make it easy to update the boot files or to make   
   it difficult? AFAICS it's an open question. I don't know if there is one   
   right answer.   
      
   If I wanted to make it difficult then I could store boot code in special   
   locations. But the whole point of looking through the root directory is   
   to treat the OS loader as a normal file so that updates are easier and   
   the process is more transparent.   
      
   >>   
   >> Most OSes have special utilities which you're probably aware of that   
   >> place system files and structures into their proper locations on the   
   >> hard disk.  Yes?   
      
   I agree that boot steps often use non-standard mechanisms. Whether they   
   should or not is another matter.   
      
   ...   
      
   >>> with mkfs.fat (or mkfs.vfat)   
   >>   
   >>  From Linux for FAT16, I had to do something like:   
   >> (I'm unsure if this is complete ...)   
   >>   
   >> ms-sys /dev/sdc   
   >> mkfs.vfat -v -F 16 /dev/sdc1   
   >> ms-sys -6 /dev/sdc1   
   >>   
      
   I'd never heard of ms-sys and it's not part of my distribution but it   
   looks useful.   
      
      
   >>   
   >   
   > Oops, that's not complete ...   
   >   
   > dd if=/dev/zero of=/dev/sdc count=16470 bs=512   
   > fdisk /dev/sdc   
   >   
   > /* now the stuff above */   
      
   I do similar:   
      
      dd bs=1024 count=20480 if=/dev/zero of=1-flat.vmdk   
      sfdisk .... [see below]   
      sudo losetup --show -Pf 1-flat.vmdk   
      sudo mkfs.fat -h 2048 /dev/loop???p1  {with ??? replaced}   
      
   Then   
      
      dd bs=1 count=446 ${DDPARMS} if=mbr of=1-flat.vmdk   
      dd bs=1 count=2   ${DDPARMS} if=mbr of=1-flat.vmdk skip=510   
      dd bs=1 count=3   ${DDPARMS} if=vbr of=${PBEG}   
      dd bs=1 count=450 ${DDPARMS} if=vbr of=${PSTA} skip=62   
      
   where   
      DDPARAMS is conv=notrunc status=none   
      PBEG is 1-flat.vmdk seek=$(( 2048 * 512 ))   
      PSTA is 1-flat.vmdk seek=$(( 2048 * 512 + 62 ))   
      
   Block 2048 is where the partition begins.   
      
   >   
   > The options used for Linux fdisk were: c n p 1 a t e w   
   >   
   > That was for 16470 sectors for 8MB FAT16.   
   >   
   > For a floppy, count=1440.   
   >   
   > Just an FYI, I'm not sure why I was using fdisk with a floppy   
   > image/disk, but the Linux fdisk options I used were: n p 2 t 11 w.   
   >   
   > If you're not familiar with Linux fdisk, you'll have to work through   
   > those Linux fdisk options on your own, as I think some of them required   
   > inputting information, like partition size or starting track number,   
   > etc.   
      
   Rather than controlling fdisk manually one can recreate a partition   
   table from a text file. For example, I use   
      
   sfdisk 1-flat.vmdk <