Ubuntu 9.10 Karmic Koala Server Edition is available for download, but if you already used Ubuntu 9.04 Jaunty Jackalope Server Edition, you can do these steps to upgrade to 9.10. Here are what you have to do:

1. install update-manager-core package (in case it's not installed yet)
2. edit /etc/update-manager/release-upgrades

Prompt=normal

3. # sudo do-release-upgrade -d
4. wait till upgrade process succeed


And if you have Desktop System, you can do these:

1. Press Alt+F2 on your GUI
2. Type in "update-manager -d" (without quotes)
3. Update Manger should open up, and you can see "New distribution release '9.10' is available"
4. Press the 'Upgrade' button, and wait till upgrade process succeed