Fedora includes multiple best of breed free software Java(TM) implementations, obtained through active adoption of innovative technology integrations produced by Fedora and others within upstream projects. The implementations integrated into Fedora are based on OpenJDK (http://openjdk.java.net/) and the IcedTea GNU/Linux distribution integration project (http://icedtea.classpath.org/), or based on alternatives such as the GNU Compiler for Java (GCJ - http://gcc.gnu.org/java and the GNU Classpath core class libraries (http://www.gnu.org/software/classpath/). All Fedora innovations are pushed upstream to get the widest possible integration of the technologies in general Java implementations.

The implementation of OpenJDK 6 included in Fedora 10 uses the HotSpot virtual machine runtime compiler on x86, x86_64, and SPARC. On PowerPC (PPC) it uses the zero interpreter, which is slower. On all architectures an alternative implementation based on GCJ and GNU Classpath is included that includes an ahead-of-time compiler to produce native binaries.

Fedora binaries for selected architectures (currently only x86 and x86_64 based on OpenJDK) are tested against the Java Compatibility Kit (JCK) by Red Hat to guarantee 100% compatibility with the Java Specification (JDK 1.6 at this time).

In Fedora 10 gcjwebplugin has been replaced by IcedTeaPlugin that runs untrusted applets safely in a Web browser and works on any architecture. You can see which Applet Plugin is installed by typing about:plugins in Firefox. The new plugin adds support for the JavaScript bridge (LiveConnect) that was missing from earlier versions. For more details on "bytecode-to-JavaScript bridge (LiveConnect)", refer to the bug report:

https://bugzilla.redhat.com/show_bug.cgi?id=304021

Feedback on the security policy is very appreciated. If you suspect the security policy may be too restrictive to enable restricted applets, run the firefox -g command in a terminal window to see what is being restricted, then grant the restricted permission in the /usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0/jre/lib/security/java.policy file. If you then file a bug report, your exception could end up in the packaged security policy and you won't have to hack the policy file in the future.

Experimental Web Start (javaws) support via NetX has been added to the IcedTea repository. When a Java Network Launching Protocol (.jnlp) file is embedded on a web page you can open it with the IcedTea Web Start (/usr/bin/javaws).

http://jnlp.sourceforge.net/ -- NetX

Through the IcedTea project, OpenJDK has been integrated with several new technologies that are also part of Fedora 10.

jvisualvm

Fedora 10 includes many packages derived from the JPackage Project.

http://jpackage.org

Some of these packages are modified in Fedora to remove proprietary software dependencies, and to make use of GCJ's ahead-of-time compilation feature. Use the Fedora repositories to update these packages, or use the JPackage repository for packages not provided by Fedora. Refer to the JPackage website for more information about the project and the software it provides.

	Mixing Packages from Fedora and JPackage
	Research package compatibility before you install software from both the Fedora and JPackage repositories on the same system. Incompatible packages may cause complex issues.

Since Fedora 9 the packages called java-1.7.0-icedtea* in Fedora 8 have been renamed to java-1.6.0-openjdk*. The Fedora 8 IcedTea packages tracked the unstable OpenJDK 7 branch, whereas the java-1.6.0-openjdk* packages track the stable OpenJDK 6 branch. All the upstream IcedTea sources are included in the java-1.6.0-openjdk SRPM.

If you are upgrading from a system based on Fedora 8 that still has IcedTea installed, the package changeover does not happen automatically. The packages related to IcedTea based on OpenJDK 7 must first be erased, then the new OpenJDK 6 packages installed.

      su -c 'yum erase java-1.7.0-icedtea{,-plugin}' su -c 'yum install java-1.6.0-openjdk{,-plugin}'
    

Upgrading from Fedora 9 does not require special action.

Fedora may include additional patches to the kernel for improvements, bug fixes, or additional features. For this reason, the Fedora kernel may not be line-for-line equivalent to the so-called vanilla kernel from the kernel.org web site:

http://www.kernel.org/

To obtain a list of these patches, download the source RPM package and run the following command against it:

      rpm -qpl kernel-<version>.src.rpm
    

To retrieve a log of changes to the package, run the following command:

      rpm -q --changelog kernel-<version>
    

If you need a user friendly version of the changelog, refer to http://wiki.kernelnewbies.org/LinuxChanges. A short and full diff of the kernel is available from http://kernel.org/git. The Fedora version kernel is based on the Linus tree.

Customizations made for the Fedora version are available from http://cvs.fedoraproject.org.

Fedora 10 includes the following kernel builds:

You may install kernel headers for all four kernel flavors at the same time. The files are installed in the /usr/src/kernels/<version>[-PAE|-xen|-kdump]-<arch>/ tree. Use the following command:

      su -c 'yum install kernel{,-PAE,-xen,-kdump}-devel'
    

Select one or more of these flavors, separated by commas and no spaces, as appropriate. Enter the root password when prompted.

	x86 Kernel Includes Kdump
	Both the x86_64 and the i686 kernels are relocatable, so they no longer require a separate kernel for kdump capability. PPC64 still requires a separate kdump kernel.

	Default Kernel Provides SMP
	There is no separate SMP kernel available for Fedora on i386, x86_64, and ppc64. Multiprocessor support is provided by the native kernel.

	PowerPC Kernel Support
	There is no support for Xen or kdump for the PowerPC architecture in Fedora. 32-bit PowerPC does still have a separate SMP kernel.

Fedora 10 does not include the kernel-source package provided by older versions since only the kernel-devel package is required now to build external modules. Configured sources are available, as described Section 8.3.3, “Kernel flavors”.

	Custom Kernel Building
	For information on kernel development and working with custom kernels, refer to http://fedoraproject.org/wiki/Building_a_custom_kernel

Refer to http://kernel.org/pub/linux/docs/lkml/reporting-bugs.html for information on reporting bugs in the Linux kernel. You may also use http://bugzilla.redhat.com for reporting bugs that are specific to Fedora.