sys

  sys [[d:]path] d: [bootsect] [switches]

Options

  [[d:]path]
  The (optional) location of the system files.
  If not given, the current directory is assumed.

  d:
  The drive to make bootable.

  bootsect
  The name of file, to which the 512-byte boot sector image
  will be written.
  (the drive's real boot sector won't be
   written to unless BOTH is used.)

Switches (FreeDOS specific):

  /BOTH
  The new boot sector will be written to the image file
  and to the actual drive boot sector.

  /BOOTONLY
  With this option the boot sector (or image) will be updated,
  but the kernel and command.com will
  not be copied to the destination.

  /UPDATE
  This option is for updating (or changing) your kernel while
  leaving your shell alone.  Updates the boot sector and copies
  the kernel file(s) to the destination.  [Allows installing
  latest kernel and boot sector without making a copy of your
  current COMMAND.COM or other shell first.]  Note: for FreeDOS
  kernel, an upgrade can also be performed by simply copying
  KERNEL.SYS over an existing bootable one (though making a 
  backup of your current kernel is encouraged).

  /K filename
  Gives the filename of the kernel file to be copied. This option
  is only required when the kernel is not called "kernel.sys"
  Note: when combined with the /L option, allows one to use FreeDOS
  sys to create a system to boot custom kernels (ie custom OS)

  /L segment
  The load segent, in hexadecimal, to use. The default is 0x60.

  /B btdrv
  Sets the BIOS boot drive # (in hex) stored within the boot sector.

  /FORCEDRV
  Causes the boot sector to only use the btdrv indicated in
  boot sector.  NOPs the code that normally uses BIOS provided
  drive # passed at boot time in the DL register.

  /BACKUPBS [path]filename
  The original boot sector is written to [path]filename prior
  to overwriting with FreeDOS one.  The filename may refer to any
  [image or bs] file, if exists only the 1st 512 bytes will be
  overwritten.

  /DUMPBS [path]filename
  The original boot sector is written to [path]filename and
  then exits.  The filename may refer to any [image or bs] file,
  if exists only the 1st 512 bytes will be overwritten.
  Note: /backupbs is intented to provide a backup of existing
  boot sector in case one wishes to restore it later (see /restorbs),
  whereas /dumpbs is intended only as a convenient method to
  obtain current boot sector (such as for debugging purposes or
  alternate installation scenerios).

  /RESTORBS [path]filename
  Restores original boot sector ([path]filename) and exits.
  The boot sector specified is written with no modifications.
  The filename may refer to any [image or bs] file, only the 1st
  512 bytes are used.

  /OEM:DOS
  Where DOS is one of
    AUTO - the default, attempts to determine automatically,
                  checking for FreeDOS, DR-DOS, PC-DOS, then MS-DOS;
    FD   - FreeDOS mode, setup destination drive to boot
                  the FreeDOS kernel and copy FreeDOS system files
                  (default to KERNEL.SYS and load segment of 0x60)
    DR   - use DR DOS 7+ (including Udo Kuhnt's DR-DOS
                  Enhanement Project) compatible settings
                  (use IBMBIO.COM & IBMDOS.COM, and loadseg=0x70)
    PC   - use PC-DOS (any) compatible settings, including
                  alternate boot sector (supports FAT12/16 only)
                  Must be explicitly choosen, AUTO selects DR mode.
                  (use IBMBIO.COM & IBMDOS.COM, and loadseg=0x70)
    MS   - use MS-DOS (pre 7) compatible settings, including
                  alternate boot sector (supports FAT12/16 only)
                  (use IO.SYS & MSDOS.SYS, and loadseg=0x70)
    W9x  - use MS-DOS 7+, aka Windows 9x DOS compatible
                  settings, Win ME unsupported ...

  Note: when attempting to boot older PC/MS DOS versions, even when
  using the alternate boot sector, one may need to ensure the
  system files are the 1st two filesystem entries and in consecutive
  sectors at the beginning of the drive; so for best results when
  creating a PC/MS DOS boot disk, format the drive first, do NOT
  create a label, and then run sys on it.  You can then add a label.
  Newer releases, such as PC-DOS 7.x do not have these limitations.