I am not a DB2 expert but needed a "real" database for my test IBM Portal 126.96.36.199 installation on my laptop. This is how I got it working.
I chose to install DB2 Express 9.7 onto my laptop. It is just for testing and demo purposes but using DB2 Express over the standard "derby" database makes the Portal respond very much faster.
Firstly, the install wizard had a few issues displaying screens correctly. So to ensure you get the correct screens, set you ubuntu screen "System > Preferences > Appearances", "Visual Effects" Tab to "None". If you don't do this you will not see the installation messages correctly.
1) Ensure you have the linux 64 bit version of DB2 Express 9.7 from IBM and the necessary license file. The 64 bit linux version will be a tar file:
yoiu may need libaio so get this with:
$ sudo apt-get install libaio1
2) Extract the tar file to a temp folder for db2. It will create a folder "exp"
$ cd ~/tmp/db2
$ su root
# cd exp
# ./db2setup (graphical)
# ./db2_install (console)
If you choose the graphical option then the graphical installation startup screens are shown (it pauses for a while whilst the wizard screens are being prepared). Navigate on the left hand side to "Install a Product" then choose the "Install New" button.
A new graphical wizard will start
1) Accept license agreement (you still need a license key later anyhow) and click "Next>"
2) Choose installation type - I choose "Typical 900-1090 MB". click "Next>"
3) At "Select installation, repsonse file creation, or both" screen, I chose "Install DB2 Express on this computer and save my settings in a response file". I left the response file name standard of: "/root/db2exp.rsp". Click "Next>"
4) At the "Select the installatin directory" screen, leave the default of "/opt/ibm/db2/V9.7" and click "Next>"
5) At the "Set up a DB2 instance" choose "Create a DB2 instance" and click "Next >"
6) At the next screen accept defaults to create the administration user. Enter password and "Confirm password" and click "Next>"
7) At the "Set user information for the DB2 instance owner" leave default to create the owner "db2inst1". Enter "Password" and "Confirm password" screens and click "Next>"
8) At the "Set user information for the fenced user" accept defaults to create a new fenced user (db2fenc1). Enter "Password" and "Confirm password" screens and click "Next >"
9) The next screen is a summary of your responses. Click "Finish" to start the installation.
When you have finished you can start the DB2 instance by logging on as the db2inst1 user as a new login session and then use the db2start command:
$ su - db2inst1
To stop the instance
$ su - db2inst1
By the way, ff you forget any of your responses you can simply open the /root/db2exp.rsp file and take a look at what you typed (passwords are not held in clear text in this file!)