Updated description of boot sectors by sparse info about PReP, CHRP.
Described the layout for GRUB2 based hybrid images.
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@ -17,9 +17,9 @@ EL Torito CD booting, for PC-BIOS x86, PowerPC, (old) Mac, EFI.
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Master Boot Record (MBR), for PC-BIOS x86 from (pseudo-) hard disk
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Apple Partition Map (APM)
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Apple Partition Map (APM), for more modern Mac
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GUID Partition Table (GPT)
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GUID Partition Table (GPT), for EFI from (pseudo-) hard disk
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MIPS Volume Header, for MIPS Big Endian, e.g. SGI Indigo2.
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@ -27,10 +27,16 @@ DEC Boot Block, for MIPS Little Endian , e.g. DECstation.
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SUN Disk Label and boot images, for SUN SPARC
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PowerPC Reference Platform (PReP), for IBM PowerPC
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Common Hardware Reference Platform (CHRP), for IBM PowerPC
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Combinations of boot mechanisms:
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- SYSLINUX isohybrid MBR
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- SYSLINUX isohybrid for MBR, UEFI and x86 Mac
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- GRUB2 grub-mkrescue MBR
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>>> Mac and/or PowerPC bootable GRUB2 image with HFS+/FAT, APM,
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EFI GPT partition, PreP MBR partition, mountable FAT partition
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------------------------------------------------------------------------------
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@ -50,7 +56,13 @@ with arbitrary content. This prescription is obeyed by PC-BIOS systems only
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if the ISO 9660 image is presented on CD, DVD or BD media.
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In this case the El Torito Boot record is the starting point of booting.
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The Boot Record is a ECMA-119 Volume Descriptor which is eventually located
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After the System Area, an ISO 9660 image usually has three distinct block
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intervals for:
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- Volume descriptors (Primary Volume Descriptor, Boot Record, Joliet, ...)
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- Directory trees, tables, boot catalog, embedded partitions and filesystems.
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- Data file content, including content of El Torito boot images.
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The Boot Record is an ECMA-119 Volume Descriptor which is eventually located
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at 2 kB block number 17 (decimal). Its content points to the location of the
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Boot Catalog.
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The format is described in part by ECMA-119 8.2 "Boot Record" and further
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@ -373,8 +385,8 @@ HFS+ filesystem.
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Block0 of an APM begins at byte 0 of the medium. Thus it collides with MBR and
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other boot sector formats. By lucky coincidence it is possible to compose
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a mock-up of a Block0 which is acceptable to firmware which expects APM,
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and is also harmless x86 machine with no negative side effects.
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So it is possible to combine APM with specially prepared MBR.
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and is also harmless x86 machine code with no negative side effects.
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So it is possible to combine APM with an especially prepared MBR.
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The layout of a Block0 of an APM is:
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@ -424,6 +436,7 @@ Byte Range | Value | Meaning (all numbers are stored big endian)
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| | bit1= entry is allocated
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| | bit4= partition is readable
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| | bit5= partition is writable
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| | bit30= automatic mount (legacy Mac)
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92 - 95 | boot_block | Logical start block number of boot code = 0
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96 - 99 | boot_bytes | Number of bytes in boot code = 0
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100 - 119 | | More boot code stuff = 0
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@ -457,11 +470,11 @@ start_block = start_of_hfs
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block_count = end_of_hfs - start_of_hfs
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name = "HFSPLUS_Hybrid"
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type = "Apple_HFS"
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flags = 0x13
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flags = 0x40000013
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Entry 4 (byte 0x2000) describes the interval from the end of the HFS+
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partition to the end of the ISO image. It is possible that this interval is
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empty. In this case, no forth APM entry will be written.
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empty. In this case, no fourth APM entry will be written.
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start_block = end_of_hfs
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block_count = end_of_iso - end_of_hfs
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name = "Gap1"
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@ -479,7 +492,7 @@ flags = 0x13
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GUID Partition Table (GPT)
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for alternative mountability paths
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and for booting of some Apple Macs from (pseudo-) hard disk
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and for EFI booting of some Apple Macs from (pseudo-) hard disk
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Sources:
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http://mjg59.dreamwidth.org/11285.html
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@ -536,6 +549,7 @@ A globally registered class of GUID are the partition type GUIDs.
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This example uses two of them
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Basic data partition: a2 a0 d0 eb , e5 b9 , 33 44 , 87 c0 68 b6 b7 26 99 c7
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HFS+ partition : 00 53 46 48 , 00 00 , aa 11 , aa 11 00 30 65 43 ec ac
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EFI System partition: 28 73 2a c1 , 1f f8 , d2 11 , ba 4b 00 a0 c9 3e c9 3b
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Note that the wikipedia list shows the first 32-bit word and the next two
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16-bit words in little-endia interpretation.
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@ -581,6 +595,11 @@ Byte Range | Value | Meaning (little endian numbers, LBA unit is 512 byte)
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| | Points to start of backup partition table.
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---------- | ---------- | ----------------------------------------------------
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An EFI System partition usually contains the same data blocks as the El Torito
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boot image for EFI. It is used for booting some Macs from (pseudo-) hard disk.
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------------------------------------------------------------------------------
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@ -866,6 +885,36 @@ Byte Range | Value | Meaning
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---------- | ---------- | ----------------------------------------------------
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------------------------------------------------------------------------------
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PowerPC Reference Platform (PReP)
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for IBM PowerPC
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Sources:
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Mail conversations with Vladimir Serbinenko.
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PReP boots via a MBR partition containing only raw ELF and having type 0x41.
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------------------------------------------------------------------------------
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Common Hardware Reference Platform (CHRP)
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for IBM PowerPC
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Sources:
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Mail conversations with Vladimir Serbinenko.
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CHRP is marked by an MBR partition entry of type 0x96 spanning the whole
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ISO 9660 image.
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PReP boot may be preferable. At least it can co-exist with other partitions
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in the ISO image.
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------------------------------------------------------------------------------
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>>> ??? HP-PA
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@ -1299,9 +1348,73 @@ Vladimir Serbinenko about the partition table entry:
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------------------------------------------------------------------------------
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>>> Mac bootable GRUB2 image with HFS+ and APM
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>>> ? With EFI partition ?
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>>> ? With PC-BIOS MBR ?
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>>> Mac and/or PowerPC bootable GRUB2 image with HFS+/FAT, APM,
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EFI GPT partition, PreP MBR partition, mountable FAT partition
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>>> ? With PC-BIOS MBR x86 Code ?
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This storage layout was mainly defined by Vladimir Serbinenko. It relies much
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on the embedded HFS+/FAT filesystem for which he provided the code to libisofs.
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Start Blocks (2 KiB):
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0 System Area
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16 Volume Descriptors
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TREE ISO-RR tree, Joliet tree, other trees and meta data, except HFS+/FAT
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EFI EFI boot image partition (optional)
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PREP Prep image partition (optional)
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HFAT HFS+/FAT metadata (optional)
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DATA Data file content (including El Torito boot images)
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HFSB HFS superblock backup (if HFS+/FAT metadata)
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TAIL Further tails and paddings (optional)
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GPTB GPT backup (if GPT in System Area)
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END End of ISO image
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System Area may contain simultaneously:
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MBR (x86 boot code must leave room for 8 bytes mock-up of APM Block0)
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APM
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GPT
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MBR Partitions:
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0xee from 0 to PREP-1, protective partition, announcing presence of GPT
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0x41 from PREP to HFAT-1, PreP partition
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0x0c from HFAT to END-1, FAT partition, bootable bit on
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0x00 Empty partition
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GPT Partitions:
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The primary GPT itself covers the System Area.
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Basic Data from 16 to EFI-1, protects first part of ISO image
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EFI System from EFI to PREP-1, offers EFI image for booting
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Basic Data from PREP to HFAT-1, protects PreP partition
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HFS+ from HFAT to TAIL-1, offers HFS+ for mounting
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Basic Data from TAIL to GPTB-1, protects rest of ISO image (if there is)
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APM Partitions:
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The range from end of APM to end of System Area stays unprotected.
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(The primary GPT might sit there.)
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Apple_partition_map from 1 to 3 or 4, covers the APM itself
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ISO9660_data from 16 to HFAT-1, covers first part of ISO image
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Apple_HFS from HFAT to GPTB-1, offers HFS+ for boot and mount
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ISO9660_data from GPTB to END-1, covers rest of ISO image
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(might be omitted if empty)
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El Torito:
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Boot image for 80x86 PC-BIOS
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Boot image for EFI (usually the same file as the partition EFI to PREP-1).
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If optional components are not present, then their addresses coincide with
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the address of the next component that is present. E.g. HFAT == DATA if no
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HFS+/FAT filesystem is present.
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If no FAT filesystem is present within HFS+/FAT, then the type of the last
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partition is 0xcd.
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If neither EFI, nor PreP, nor FAT within HFS+/FAT, are present, then there
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is only one partition. It has type 0xee, if GPT is present in the System Area.
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It has type 0xcd and offset 1*512, if no GPT is present.
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Involved -as mkisofs options:
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-hfsplus
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-fat
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-efi-boot-part DISKFILE
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-prep-boot-part DISKFILE
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------------------------------------------------------------------------------
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