12.04 grub doesn't see secondary btrfs installation

[Nick Payne]

I've had 12.04 amd64 running for a couple of weeks without any problem. I just did a second install of 12.04 onto a secondary disk (everything in a single partition on /dev/sdc1), using btrfs for the file system, and telling the install to put grub onto sdc, so that I didn't interfere with grub onto the default boot disk.

Install ran successfully, I then booted back into my main installation and ran "sudo update-grub". However, update-grub doesn't see the new installation on the btrfs partition. Is there something extra I need to do for update-grub to see this installation?

[Nick Payne]

p.s. I found that if I copy the menu entries for booting the secondary installation from its grub.cfg to the custom section of the grub.cfg for the primary installation, then I can boot into the secondary installation ok. But why doesn't update-grub see that installation?