Boot CD ROM Builder

Boot CD-ROM Builder

Builder for bootable CD-ROM ISO images in JNode's build system.

Overview

The Boot CD-ROM Builder is the build system component that assembles all JNode artifacts (boot image, init-jar, GRUB bootloader) into a bootable ISO-9660 formatted CD-ROM image. It is invoked by the cdrom, cdrom-lite, and cdrom_64-lite targets in the build system.

Key Components

File	Purpose
all/build.xml	Master build file, defines CD-ROM targets
all/build-x86.xml	Contains create-cdrom macro and cdrom/cdrom-lite targets
builder/lib/iso9660.jar	ISOTask library for ISO-9660 image creation

How It Works

Build Targets

The build system exposes three CD-ROM targets:

sh build.sh cd-x86        # Full distribution ISO
sh build.sh cd-x86-lite  # Lite x86 ISO
sh build.sh cd-x86_64-lite # Lite x86_64 ISO

create-cdrom Macro

The create-cdrom macro in all/build-x86.xml:286 assembles the CD-ROM contents:

Directory contents:
  ├── boot/grub/           GRUB boot files (eltorito.s2, fat.s15, grub.s1, grub.s2)
  ├── boot/grub/menu.lst   Boot menu configuration
  ├── licenses/            License files
  ├── jnode*.gz            Boot image (compressed kernel)
  └── initjars/            Plugin JARs and descriptors

ISO Creation

The macro supports two ISO creation backends:

1. mkisofs (Unix/Linux): Uses the system mkisofs utility with El Torito boot catalog

   mkisofs -o <destfile> -R -b boot/grub/eltorito.s2 \
     -no-emul-boot -boot-load-size 4 -boot-info-table <dir>
   

2. ISOTask (cross-platform): Uses de.tu_darmstadt.informatik.rbg.hatlak.iso9660.ISOTask from iso9660.jar

   • enableRockRidge: Enables Rock Ridge extensions for Unix-style filenames
   • mkisofsCompatibility: Ensures compatibility with mkisofs-generated images
   • bootImage: Specifies the El Torito boot image
   • bootImageSectorCount: Boot image size in sectors (4 for GRUB)
   • genBootInfoTable: Generates boot info table for BIOS

Boot Image Structure

The CD-ROM follows this layout:

Component	Location	Purpose
Boot image	Root	jnode*.gz - compressed boot image
Init JAR	Root	initjars/ - all plugin JARs
GRUB	boot/grub/	Bootloader stages
Menu	boot/grub/menu.lst	Boot configuration
Licenses	licenses/	GPL/LGPL license files

GRUB Configuration

The menu.lst file is copied from all/conf/menu-cdrom.lst and provides boot menu options. GRUB is configured to:

• Boot from El Torito emulation (no-emulation boot)
• Load the boot image from CD-ROM
• Pass multiboot parameters to the kernel

ISOTask Library

The ISOTask library (de.tu_darmstadt.informatik.rbg.hatlak.iso9660.ISOTask) is a Java-based ISO-9660 image creator that:

• Implements ISO-9660 Level 1 and Level 2 formats
• Supports Rock Ridge extensions for long filenames
• Generates El Torito bootable CDs
• Provides mkisofs-compatible output

Gotchas

• Platform dependency: The mkisofs path is Unix/Linux only; Windows builds must use ISOTask
• mkisofs spaces issue: Build fails on Windows if the path contains spaces
• Boot image size: The boot image sector count (4 sectors = 2KB) must match GRUB expectations
• ISOTask classpath: The iso9660.jar must be in the build classpath for ISOTask to work
• Rock Ridge: Enabled by default but can affect compatibility with non-Unix systems
• Output path: CD-ROM images are written to all/build/cdroms/jnode-*.iso

Related Pages

• Build-System — Build system overview
• Boot-Sequence — What happens after the ISO boots
• Boot---BootImageBuilder-Internals — Boot image construction
• ISO9660 — ISO-9660 filesystem standard