Is it possible to install Ubuntu in Tablets & Smartphones

I have heard some devices come with Ubuntu installed but is it possible to install it on Tablets and Smartphones that do not have Ubuntu preinstalled.

Solution 1:

https://wiki.ubuntu.com/ARM

From there:

ARM Processor

ARM is a processor architecture used in a variety of applications, such as:

• Handheld Computers (Nokia n900, n95, etc.)
• Network Devices (Genesi Efika MX Nettop, Wyse T50, CompuLab TrimSlice, etc.)
• Project development boards (Beagleboard, Pandaboard, Quickstart, etc.) Subnotebooks (Sharp Netwalker, etc.)
• Netbook/Notebooks (Genesi Efika MX Smartbook, Toshiba AC100, etc.)
• Ubuntu targets the ARMv7 and above Application Processor family (Cortex A8, A9 and above). Currently the archive supports ARM EABI, with an expectation of minimum compliance with the ARMv7+VFP ISA. Where possible Ubuntu targets the Thumb2 instruction set.

Limited support for earlier instruction sets (ARMv5t, ARMv6) was available in early releases of the ARM port (jaunty, karmic).

Status

• Much of the application porting is complete
• Installation images are available for selected boards
• kernels for a variety of sub-architectures are available
• Much of SMP validation complete
• Continued porting and optimization is underway

Current Images

ARM TEAM

• OMAP: Texas Instruments OMAP
• Tegra (AC100): Thosiba AC100 Nvidia Tegra 2
• IMX53 QuickStart: Freescale IMX53 QuickStart Board
• Server images (for OMAP3/4 so far) ARM/ServerInstall

There's more at their FAQ too, which you can check there too.