I am interested in installing to a USB drive...

[bobmatino17]

Well, I asked a similar question previously. But now I want a full install (not a live CD) on my flash drive. Is it possible to set that up within Ubuntu somehow, or would I have to burn to an optical disk first?

[mikewhatever]

It is possible, just point the installer to the desired usb drive. Obviously, you'd have to boot the installer from another media, cd or usb.

[C.S.Cameron]

Following is a step by step for installing 10.10 to 8GB USB, adjust partition size to suit:

Turn off and unplug the computer. (See note at bottom)
Remove the side from the case.
Unplug the power cable from the hard drive.
Plug the computer back in.
Insert the flash drive.
Insert the Live CD.
Start the computer, the CD should boot.
Select language
Select install Ubuntu.
Select Download updates while installing and Select Install this third-party software.
Forward
At "Allocate drive space" select "Specify partitions manually (advanced)".
Forward
Confirm Device is correct.
Select "New Partition Table" click Continue on the drop down.
Click "Free space" and "Add".
Select "Primary".
Make "New partition size..." about 1GB.
Location = Beginning.
"Use as:" = "FAT32 file system"
And "Mount point" = windows.
Select "OK"
Click "free space" and then "Add".
Select "Primary", "New partition size ..." = 3 to 4 GB, Beginning, Ext4, and Mount point = "/" then OK.
(Optional)
Click "free space" and then "Add".
Select "Primary", "New partition size ..." = 1 to 2 GB, Beginning, Ext2, and Mount point = "/home" then OK.
(Optional)
Click "free space" and then "Add".
Select "Primary", "New partition size ..." = remaining space, (1 to 2 GB), Beginning and "Use as" = "swap area" then OK.
(Importent)
Confirm "Device for boot loader installation" points to the USB drive. Default should be ok if HDD was unplugged.
Click "Install Now".
Select your location.
Forward.
Select Keyboard layout.
Forward.
Insert your name, username, password, computer name and select if you want to log in automatically or require a password.
Selecting "Encrypt my home folder" is a good option if you are woried about loosing your USB drive.
Select forward.
Wait until install is complete.
Turn off computer and plug in the HDD.
Stick the side panel back on.

Note:
You may omit disabling the hard drive if after partitioning you choose to install grub to the root of the usb drive you are installing Ubuntu to, (ie sdb not sdb1). Be cautious, many people have overwritten the HDD MBR.
At boot you will then be given the option to boot your computer's hard drive, even when booting another computer.