How to run the development release with Wubi

Prepare for breakage

This goes without saying, but I like to say it anyway. If you choose to follow these instructions, and you lose your installation/data or worse - you're on your own. That said, I've been running the development release on Wubi since 11.10 and with a few precautions you should be okay. 

Note: Since the 32-bit non-pae kernel will not be supported in 12.10, I advise not following these instructions if you are using the 32-bit non-pae kernel.

Backup and restore

Even though I am aware that things could go awry, it's still irritating to lose the install. So I keep a fully synched backup of the root.disk. After running updates (which you'll probably get used to doing every time you boot), once you've rebooted and confirmed things are stable, you can resynch your backup. 

Here's how to do it:

1. Make a copy of your root.disk using the Wubi resize script 
2. Keep it synchronized by rerunning the script, but supplying the --resume option (which will copy only files that have been modified/added and delete ones that have been removed).
3. Make the new.disk bootable (so you can confirm it works without booting to Windows to rename the disks). You do this by adding the following lines to /etc/grub.d/40_custom (changing the bits in red to match your own settings):

menuentry 'Ubuntu - backup new.disk' --class ubuntu --class gnu-linux --class gnu --class os {

        set gfxpayload=$linux_gfx_mode

        insmod part_msdos

        insmod ntfs

        set root='(hd0,msdos3)'

        search --no-floppy --fs-uuid --set=root 18B4B7BBB4B799A8

        loopback loop1 /ubuntu/disks/new.disk

        set root=(loop1)

        linux   /vmlinuz root=UUID=18B4B7BBB4B799A8 loop=/ubuntu/disks/new.disk ro   quiet splash vt.handoff=7

        initrd  /initrd.img

}

Then you'll see "Ubuntu - backup new.disk" at the bottom of the grub menu when you boot. If you don't see the grub menu, hold down the Shift key after selecting Ubuntu.

Upgrading to Quantal

Since there is no Wubi.exe version for Quantal available at this early stage of development, the only way to get it is to install 12.04 Precise Pangolin, and then modify your sources.list. (Note, once the Alpha1 is released you may be able to install normally and in this case you should not use this method).

sudo sed -i 's/precise/quantal/g' /etc/apt/sources.list

sudo apt-get update && sudo apt-get dist-upgrade 

Partial upgrades

Always review the results before running dist-upgrades. In particular, look at what is being removed. It's fairly common for the packages to be out of synch at times during the development release, and if you're not careful you might uninstall critical bits. My rule of thumb is, if anything is being deleted look for a newer version of it being installed. If there is no corresponding entry, then wait a few days. Sometimes you'll find the packages are no longer listed as being removed. In other cases, they're still there and it's probably safe to proceed. If you notice a lot of packages being deleted, run away.

Where to go for help

Please review the Sticky threads in the Ubuntu+1 forum on ubuntuforums.org. If you have any questions or problems, look there to see if someone else has a solution or post your own questions.