JNode is a Java-based operating system that is actively developed and open source. It uses a plugin framework so that everything, including the JVM and framework, can be loaded as plugins. The driver framework finds and maps hardware devices to Java drivers through extension points. Future goals include improved performance, a deployment framework, and a document-oriented desktop environment. Java benefits the OS through dynamic linking, type safety, security features, and development tools.

1. Why Java is practical for modern operating
systems
JNode.org
Ewout Prangsma
Copyright (c) JNode.org 2005 http://www.jnode.org

2. Contents
● Introduction
● History
● Characteristics
● Architecture
● Plugin framework
● Driver framework
● Future
● Java benefits
Copyright (c) JNode.org 2005 http://www.jnode.org

3. Introduction
● Simple to use & install operating system for personal
use: written for and in Java
● Targets:
– Modern devices
– Desktop
– Small servers
● Only actively developed Java OS in the open source
world
– 7 active developers, 17K downloads
Copyright (c) JNode.org 2005 http://www.jnode.org

4. History
● Original idea started in 1995
● First attempt: JBS (Java Bootable System)
– Contained C code, did not work at all
● Second attempt: JBS2
– Still did not work well, but was better
● Then: JNode
– No C code anymore, Classpath classlibraries
● Went public in May '03
Copyright (c) JNode.org 2005 http://www.jnode.org

5. Characteristics
● All Java, minimal assembler, no C
● All java build system (almost)
● Extensible architecture
● Single flat memory address space, no virtual memory
● JVM written in Java
● All Java code is compiled on the fly, no interpreter
● Security is always on
● LGPL license
Copyright (c) JNode.org 2005 http://www.jnode.org

6. Status (1)
● Release 0.2.1
– Full device driver model
– Networking TCP/IP
– Filesystems EXT2, FAT, NTFS, ISO9660
– Graphics 2D
– J2SDK 1.5 support in VM (not classlibs)
– Simple heap managers & GC
● MMTk based heap manager & GC in development
– IA32 & AMD64 platform support
Copyright (c) JNode.org 2005 http://www.jnode.org

7. Status (2)
Playing Tetris
on JNode
Copyright (c) JNode.org 2005 http://www.jnode.org

8. Architecture (1)
Desktop Deployment Debugging
Shell
framework framework framework
Build system
Driver Filesystem Partition Networking Graphics
framework framework framework framework framework
Java Virtual Machine Plugin framework
Nano kernel (asm)
Hardware
Copyright (c) JNode.org 2005 http://www.jnode.org

9. Architecture (2)
Java Virtual Machine
Classpath Runtime library
runtime library support
Class Security Native code
manager manager compilers
Scheduler &
Heap Isolation
threading
managers manager
manager
Copyright (c) JNode.org 2005 http://www.jnode.org

10. Plugin framework (1)
● Everything is contained in a plugin
– code, resources
– even JVM & the plugin framework itself
● Plugins can:
– be loaded, unloaded & reloaded (at runtime)
– depend on other plugins
– provide well known extension points
– connect to well known extension points
Copyright (c) JNode.org 2005 http://www.jnode.org

11. Plugin framework (2)
● Plugins are:
– described by a descriptor
● descriptor also contains license info
– JAR files
– inspired by Eclipse plugins
Copyright (c) JNode.org 2005 http://www.jnode.org

12. Plugin framework (3)
<plugin id=quot;org.jnode.driverquot; name=quot;JNode Driver Frameworkquot; version=quot;@VERSION@quot;
provider-name=quot;JNode.orgquot; license-name=quot;lgplquot; class=quot;org.jnode.driver.DriverPluginquot;>
<requires> General info
<import plugin=quot;org.jnode.workquot;/>
</requires> Dependencies
<runtime>
<library name=quot;jnode-core.jarquot;> Code & resources
<export name=quot;org.jnode.driver.*quot;/>
<export name=quot;org.jnode.driver.util.*quot;/>
</library>
</runtime> Well known extension
points
<extension-point id=quot;findersquot; name=quot;System device findersquot;/>
<extension-point id=quot;mappersquot; name=quot;Device to Driver mappersquot;/>
<extension point=quot;org.jnode.security.permissionsquot;>
<permission class=quot;java.util.PropertyPermissionquot; name=quot;jnode.cmdlinequot;/>
</extension>
</plugin>
Connection to well known
extension point
Copyright (c) JNode.org 2005 http://www.jnode.org

13. Driver framework (1)
contains Device drives
Bus Driver
represents hardware
finds finds
Device Device to
finder driver mapper
Copyright (c) JNode.org 2005 http://www.jnode.org

14. Driver framework (2)
Device registers API Driver
queries for API represents hardware
calls implements
Device “user” DeviceAPI
Copyright (c) JNode.org 2005 http://www.jnode.org

15. Driver framework (3)
Example: Radeon Graphicscard driver
find PCI devices PCI
finders
driver plugin
Driver
plugin
map PCI id to driver Radeon
mappers
driver plugin
Copyright (c) JNode.org 2005 http://www.jnode.org

16. Driver framework (4)
Device manager Device finder Device 2 driver mapper Driver Device
findDevices
evice
registerD
findDriver
startDevice
registerAP
I
Copyright (c) JNode.org 2005 http://www.jnode.org

17. Future
● Short term:
– Improved JVM performance (mm, compilers)
– Deployment framework
– Improved graphics
● Long term:
– Simple to use desktop environment
● Fully document oriented instead of app. oriented
– Java powered servers
● e.g. Cooperation with ApacheDS
Copyright (c) JNode.org 2005 http://www.jnode.org

18. Java benefits
● Dynamic linking
● Type safe language (even more in J2SDK 1.5)
● Security
– Security manager
– No uncontrolled memory access
● Great development tools:
– Eclipse, Ant
Copyright (c) JNode.org 2005 http://www.jnode.org

19. We need your help!
● Don't be scared of by the codebase
– Most of it is classpath libraries
● Ask questions
● Visit http://www.jnode.org
● Contact me: epr@jnode.org
Copyright (c) JNode.org 2005 http://www.jnode.org

20. Questions
Copyright (c) JNode.org 2005 http://www.jnode.org