Run update-manager -c (not -d anymore, that’s for development releases) in a shell/terminal. This is handy if you don’t get the upgrade button.
addthis_url = ‘http%3A%2F%2Fblog.beplacid.net%2F2009%2F04%2F23%2Fupgrading-to-ubuntu-904-jaunty-jackalope-from-810-or-earlier%2F’;
addthis_title = ‘Upgrading+to+Ubuntu+9.04+%28Jaunty+Jackalope%29+from+8.10′;
addthis_pub = ”;