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hi,
i'm preparing to undertake CD filesystem. but i have 3 specification now:
ISO 9660 (ECMA-119) specification
EI-Torito bootable cdrom format specification 1.1
OSTA Univeral Disk Format Specification V2.0
obviously nobody want to read them all, especially non-Eng-spoken guys like me. my purpose is to boot from cd (i dont like the grub way, because i have to support my own file system) and read(maybe someday write) files from a cd.
the problem is, i dont understand if UDF is the super-collection of the previous two, or is another thing. i hope someone can explain their relationship in detail. advising other specs is appericiated, and i'm wondering if i have to boot from CD with another specification under EFI.
thank you!

Hi,

• ISO 9660 (ECMA-119) specification: Specification for the ISO9660 file system format typically used on CDs. This file system has a number of different extensions to add various things to it:
  • Rock Ridge: adds support to POSIX/UNIX style permissions and longer file/directory names to ISO9660
  • Joliet: adds support for Unicode to ISO9660
  • El-Torito: adds support for bootable CDs to ISO9660
  • Apple ISO 9660 Extensions: adds support for several different things to make it more compatible with other file systems used by Apple
  • ISO 13490: adds multisession support to ISO9660
• OSTA Univeral Disk Format Specification: Entirely different file system that isn't related to ISO9660 at all. Typically used for DVDs (rather than CDs).

For EFI, El-Torito is used to find an "EFI system image" on the CD. The EFI system image uses the FAT32 file system (even though the CD itself is ISO9660 or something else). This is similar to using El Torito to emulate a floppy or hard disk on PC BIOS systems, where the floppy or hard disk image is stored on the CD and may use any file system (even though the rest of the CD uses ISO9660).


Cheers,

Brendan

thank you for fast reply, but can i boot with UDF? "Please refer to the "OSTA Native Implementation Specification" document for information on the Boot Descriptor." that's the only sentense about boot in UDF.

Hi,



I honestly don't know. I failed to find the "OSTA Native Implementation Specification" document, and "Universal Disk Format Specification Revision 2.60" (the latest version as far as I know) says:



"T.B.D." is an abbreviation for "To Be Done", which means they still haven't done it yet.

As far as I've been able to tell, UDF disks that are bootable are actually using UDF to store normal files/directories on the majority of the disk, but also have a minimal ISO9660 file system in a different area of the disk to allow them to keep using El-Torito for booting.


[EDIT] Now consider EFI, where a UDF disk would contain an ISO9660 area which contains an "EFI system partition" in FAT32...

"Yo dawg, we heard you like file systems; so we put a file system in your file system in your file system...."
[/EDIT]


Cheers,

Brendan

Just a small correction: Unicode is not a filesystem, no matter how often you mistype it.

Hi,



Doh. Found them and fixed them..

I keep thinking "UDF" is some sort of universal driver framework.


Cheers,

Brendan

FAT32 + ElTorito + myownfs, i won't do more.
thanks!