Can we install Ubuntu in a pen Drive? Actually, Currently, i am using window system and running shortage of space. So, i planned for installing ubuntu in my USB pen drive. But, At the time of space allocation, it didn't recognize the drive.
Short answer: Yes.
Long answer: Depending on what type of USB install you want. Persistent (saving changes) or non persistent (just like a live Ubuntu CD). For more information read this.
For a persistent install guide try this. (Example for Jaunty Jackalope)
For a non-persistent install guide try this. (Example for Hardy Heron)
If you have tried to install Ubuntu with the above guides and failed, then your USB stick may be the problem. To run an OS off a USB it needs to have good read/write speeds.
Can you elaborate on: But, At the time of space allocation, it didn't recognize the drive.