I've just finished upgrading a test Linode to Fedora Core 4 without problems, so here goes the instructions.

This was attempted with a Fedora Core 3 system upgraded from a fresh Fedora Core 2 image.

Warning

This procedure is being posted in the Xen Public Beta forum because Fedora Core 4 does not work inside UML.

From this version of the system onwards NPTL is required, and UML doesn't support that.

Procedure

1) Install the fedora-release-4 package from a Fedora Core 4 base repository.

This package will conflict with the legacy-yumconf-3 package from Fedora Legacy; you can safely remove it now you're upgrading your system.

This step will configure yum to use the repositories for Fedora Core 4.

2) Optionally, disable the fedora-extras repository.

You must do it by setting the parameter enabled to 0 in the fedora-extras.repo configuration file.

The Fedora Extras repository is huge, and parsing it makes yum consume a huge amount of memory, with consequent swapping and all the badnass that brings.

3) Check extra software and pay attention to upgraded interfaces.

Read the updated Relase Notes:

http://fedora.redhat.com/docs/release-notes/fc4/errata/

Fedora Core 4 upgrades db4 from 4.2 to 4.3. Prepare yourself by dumping databases to reload them later.

Check for the dependencies of your extra packages -- this is a system upgrade, and interfaces will be upgraded -- Fedora Core 4 upgrades python to 2.4, MySQL to 4.1, etc.

4) Issue the yum upgrade.

Do not upgrade the system in parts. Fedora Core 4 software is NPTL-based; mixing NPTL-based components and LinuxThreads-based components may not work.

In my first attempt at this procedure I followed the exact same steps I gave in my "Fedora Core 2 to Fedora Core 3" tutorial; that upgraded rpm and db4 but not glibc; rpm became then unusable due to NPTL functions not being present in the system library.

Epilogue

Fedora Core 4 runs smoothly in NPTL emulation mode under Xen. I suppose there is nothing to stop another upgrade to Fedora Core 5 using this same procedure -- maybe I'll try that in a few months.

Included in the distribution are domU kernels and related tools; so we can expect every Fedora Core release from now on to work normally as a Xen guest.

It also seems SELinux works somewhat; with some more community study, this can become a great tool to secure Xennodes.

Further note: after such a massive update, probably some new configuration files will have been installed sideways with the old ones, with the .rpmnew suffix.

List all these files with:

]# find /etc -name \*rpmnew

Inspect the differences between (say) /etc/inittab and /etc/inittab.rpmnew with:

]# diff -u /etc/inittab /etc/inittab.rpmnew

I tried it with the latest NTPL-able 2.6.16.1-linode18 kernel, and it worked.

Cheers,

Michael