Wubi boots like this:
Windows boot manager calls GRUB4DOS (wubildr.mbr)
Wubildr.mbr looks for the first wubildr it can find (on the root of any partition)
wubildr looks for the first /ubuntu/disks/root.disk it can find (on any partition).
This is why you can't have D:\ubuntu\disks\root.disk and E:\ubuntu\disks\root.disk and hope to boot them from the Windows boot manager. The wubildr can be configured to boot a different root.disk, or to boot a different folder, but it's a pain (you can't choose at boot time, instead you have to remember to switch the wubildr files before rebooting). As Karlchen pointed out, you can switch over the wubildr and then it will go to the different target (this works with Mint, but won't work if both installs are looking for /ubuntu/disks/root.disk as it will always find the first one).
Luckily Wubi uses Grub2 (that's built into the wubildr), so you have all the power of a modern bootloader/manager. You can just tell it about the other install, and then select between them. So... where to begin?
Scenario: you have 11.10 on D: and 12.10 on E:. Currently only the 11.10 install is booting. So you boot Ubuntu and add a Grub menu entry to boot the 12.10 entry by editing the file:
Code:
gksudo gedit /etc/grub.d/40_custom
And make it look like this - well, not quite like this - you need to know your partition corresponding to E: (bolded):
Code:
#!/bin/shexec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
menuentry 'Ubuntu 12.10 on E:' {
insmod ntfs
set root='(hd0,msdos3)'
loopback loop1 /ubuntu/disks/root.disk
set root=(loop1)
linux /vmlinuz root=/dev/sda3 loop=/ubuntu/disks/root.disk ro quiet splash
initrd /initrd.img
That's not the end of it unfortunately, because the wubildr will be periodically updated when you get grub updates, and you don't want the 12.10 Grub trying to load the 11.10 grub.cfg. These are not compatible between versions.
So you would boot the 12.10 install and make sure it doesn't try to update the wubildr by editing the grub-mkimage file included with lupin (the thing that's required to allow grub to loop mount wubi installs):
The following is a diff of my /usr/share/lupin-support/grub-mkimage from some version or other of grub. You'll need to add a line "exit 0" somewhere to stop it generating the wubildr.
Code:
--- /mnt/usr/share/lupin-support/grub-mkimage 2011-09-20 03:44:44.000000000 -0700
+++ /usr/share/lupin-support/grub-mkimage 2012-10-29 22:02:55.784517389 -0700
@@ -112,7 +112,7 @@
exit 1
fi
fi
-
+exit 0 # for raring test install, bypass creation of wubildr
wubildr_partitions="$(find_wubildr)"
if [ ! -f "$target" ] && [ -z "$wubildr_partitions" ]; then
This is a lot of work... it's doable, but it's not really what Wubi was intended for. I'll help you get it setup if you want, but you need to understand that it requires a bit of hacking.
Adv Reply
Originally Posted by oldfred
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