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Oscdimg, El Torito, and UDF RRS feed

  • Question

  • Oscdimg is a command-line tool for creating an image file (.iso) of a customized 32-bit or 64-bit version of Windows PE.

    Oscdimg supports ISO 9660, Joliet, and Universal Disk Format (UDF) file systems.

    It is unclear how "El Torito File System" fits into the picture for UDF file systems.

    "-b location" specifies the location of the El Torito boot sector file.

    E.g., -bC:\Directory\Etfsboot.com

    If you want only an EFI boot, is -bC:\Directory\Etfsboot.com necessary?

    If you have a UDF only file system and BIOS only boot, is -bC:\Directory\Etfsboot.com necessary?

    If you have a UDF only file system and EFI only boot, is -bC:\Directory\Etfsboot.com necessary?

    You get the idea, what file systems and what BIOS (UEFI BIOS) require "El Torito File System using -bC:\Directory\Etfsboot.com?

    Thanks in advance.



    • Edited by petrula Sunday, January 4, 2015 12:45 AM
    Sunday, January 4, 2015 12:41 AM

Answers

  • El Torito is an addition to the CD-ROM format that allows BIOS machines to boot directly off the CD.

    El Torito is only required for BIOS systems, and is not necessary for uEFI.

    El Torito is independent of the file system on the CD or DVD (ISO 9660 or UDF).


    Keith Garner - Principal Consultant [owner] - http://DeploymentLive.com

    Tuesday, January 6, 2015 12:00 AM
    Moderator

All replies

  • El Torito is an addition to the CD-ROM format that allows BIOS machines to boot directly off the CD.

    El Torito is only required for BIOS systems, and is not necessary for uEFI.

    El Torito is independent of the file system on the CD or DVD (ISO 9660 or UDF).


    Keith Garner - Principal Consultant [owner] - http://DeploymentLive.com

    Tuesday, January 6, 2015 12:00 AM
    Moderator
  • Keith - Thanks for the feedback.

    Using "copype amd64   C:\WinPE_amd64", the following two files appear:

    C:\ WinPE_amd64\fwfiles\efisys.bin

    C:\ WinPE_amd64\fwfiles\etfsboot.com

    Using Makewinpemedia to make the ISO via

    Makewinpemedia /iso   H:\WinPE_amd64   H:\WinPE_amd64\winpe_amd64.iso

    The following two files do not explicitly appear on the DVD Disc.

    1) etfsboot.com (This is the El Torito boot sector file put into the DVD) ETFS is short for "El Torito File System"

    2) efisys.bin does not appear explicitly in the ISO so where exactly does it go and what is its purpose? Obviously, it has to do with the EFI, but you indicated that  El Torito does not contain EFI stuff.

    Thanks in advance. 

    Tuesday, January 6, 2015 11:03 PM
  • The following two files do not explicitly appear on the DVD Disc.

    That is correct, they do *NOT* appear within the CD or DVD File system, however they *ARE* there, and there are even files that allow you to extract out the boot images.

    2) efisys.bin does not appear explicitly in the ISO so where exactly does it go and what is its purpose? Obviously, it has to do with the EFI, but you indicated that  El Torito does not contain EFI stuff.

    Yea, my comment above (#2) above may be wrong. looks like efisys.bin may be present in the ISO image for use by the uEFI boot loader.


    Keith Garner - Principal Consultant [owner] - http://DeploymentLive.com

    Tuesday, January 6, 2015 11:14 PM
    Moderator
  • Keith - I appreciate you answering these questions. I cannot find detailed documention which would answer these questions so I have to ask them on the forum.

    Continuing our discussion, one can create an image file for either a BIOS-based or UEFI-based computer by using a multi-boot command. From the documentation, for example:

    Oscdimg -m -o -u2 -udfver102 -bootdata:2#p0,e,bC:\winpe_x86\Etfsboot.com#pEF,e,bC:\winpe_x86\Efisys.bin C:\winpe_x86\ISO C:\winpe_x86\winpex86uefi.iso

    "where this command starts the Etfsboot.com boot file for a BIOS image, and then starts the Efisys.bin boot file for a UEFI image."

    What is strange is that the Efisys.bin is placed somewhere. If I understand the EFI documentation, EFI does not imbed stuff in boot sectors, but instead likes to explicitly have EFI stuff as files. So we are back to the question, where exactly does Oscdimg embed efisys.bin since etfsboot.com is already in the boot sector? Thanks


    • Edited by petrula Wednesday, January 7, 2015 12:09 AM
    Wednesday, January 7, 2015 12:00 AM
  • Correct, most uEFI files are placed in Fat32 System partition(s).
    However oscdimg.exe -bootdata:xxx entries are not placed on the file system but elsewhere on the disk.

    Keith Garner - Principal Consultant [owner] - http://DeploymentLive.com

    Wednesday, January 7, 2015 12:08 AM
    Moderator