There's a page on upgrading Air 1.5 to 2.0 which suggested to run the following command on Ubuntu 9.04 (also works on 9.10)
sudo getlibs -l libhal-storage.so.1
Now if you download the Air 2 Beta Runtime using the "Download for Linux (BIN, 10.7MB)" (direct link) you can:
chmod +x air2_b1_runtime_lin_111709.bin
If you didn't use getlibs to install libhal-storage, the .bin installer will prompt you installing 32bit Air 2.0 isn't recommended on 64bit systems. Otherwise the upgrade should hopefully go well for you!