Download and Install Ubuntu
To get it on your PSP, first make sure you have Homebrew installed, i.e. not Sony's original firmware. You need at least 3.71 M33.
Download Ubuntu from http://dl.qj.net/General-Apps/pg/12/fid/17006/catid/151 and unzip the RAR file onto any directory in your hard disk.
Connect your PSP to your computer via USB and select USB Conection on your PSP.
Copy the folders PSP, PICTURE and Docs to the root of your PSP.
Copy the contents of 'seplugins' from your computer to the 'seplugins' directory in your PSP root directory.
If you notice any files have the same names, merge them.
For instance, I already have vsh.txt in F:/PSP/seplugins in my PSP with this one line:
ms0:/seplugins/screenshotbmp.prx
So, I add the lines in the vsh.txt from the Ubuntu extract into the vsh.txt in the PSP. My vsh.txt now has this:
ms0:/seplugins/ubuntu.prx
ms0:/seplugins/screenshotbmp.prx
After all the copying is done, press the O button and close the USB connection.

