How do I install Ubuntu to another partition from Ubuntu with Unetbootin?

Question

Basically what I want to do is install a fresh copy of Ubuntu from Ubuntu. It is an older machine so usb boot doesn't work and I don't see why I need to waste a CD to do it. Currently running Ubuntu 11.10.

I have a 1TB drive and a second 500GB drive for backup. The 1TB drive is partitioned as:

20GB   sda1 Windows XP
20GB   sda3 Free for new OS 
~800GB sda4 Data (ext3)
60GB   sda7 /home (ext4)
20GB   sda6 / (ubuntu 11.10 ext4)
2GB    sda5 swap

After researching I decided that using unetbootin was the best option. I chose Hard Disk (frugal install) and the only option for which disk is "/". That worked and I quickly rebooted into Ubuntu 12.04 live.

Chose to install and picked custom options, set sda3 for / and sda7 for /home. The installer started but hit a wall at detecting other operating systems. It was trying to mount sda6 to find out about the existing os's on the machine, for the purpose of installing grub. And it couldn't umount sda6 because that was currently mounted as cd drive for live cd. I couldn't find an option to make the installer skip this step (I could later fix the grub in 11.10).

I have another drive with 4GB free partition and if I could get unetbootin to install to there it would all work.

So my question is - how do I get unetbootin to install to a different disk for hard-disk install? (I don't think USB Drive mode will work because it will install the grub to that disk - but I might be wrong!)

or

How to fresh install Ubuntu from Ubuntu?

Solution

Basically Unetbootin wiki says to create a temp partition to install the live to, then install your real ubuntu in another partition and finally wipe your temporary one.

Another way to go, suggested there, would be going for the net-inst image which loads into RAM and leaves your hd free to be mounted or umounted.

Not to mention the link already provided by @Anwar Shah How to install Ubuntu from within other Linux Distributions without reboot

Comments

[ish]

I recommend you "waste" that CD, and simply install to that partition without choosing to install a bootloader. Then run sudo update-grub on your main Ubuntu installation and you should see the secondary install show up in Grub.

[Anwar]

Do you have only the Live ISO image, or the alternate iso image? If you have an alternate iso, you can install Ubuntu from Ubuntu

[Anwar]

This question might help to install ubuntu from another ubuntu if you have alternate iso askubuntu.com/q/154565/61218