Well, I've got my Penguin back in the rEFIt boot menu and everything is fine once again.
It seems that using GParted to create partitions on the Macbook internal HDD caused two problems:
1) It essentially eliminated the MBR partition table and this now consisted of just one partition extending over the whole disk
2) It corrupted the Grub bootloader on the Linux root partition
However, resolving it wasn't that difficult. Here's what I did:
1) Boot into rEFIt's Partitioning Tool and here accept the offer to update the MBR partition table.
2) Now boot to a Linux Live CD (I used Sidux as I just happened to have it lying around). Open a terminal and type:
Code:
$ sudo grub
> find /boot/grub/stage1
Here I got "(hd0,2)" which corresponds to the third partition on the Macbook internal disk which is where I have put the Ubuntu / partition.
Now, I typed the following:
Code:
> root (hd0,2)
> setup (hd0,2)
and got the following output (transcribed so it may not be exactly word perfect:
Code:
checking if "/boot/grub/stage1" exists.....yes
checking if "/boot/grub/stage2" exists.....yes
checking if "/boot/grub/stage1_5" exists.....yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0,2)"...failed (this is not fatal)
Running "embed /boot/grub/e2fs_stage1_5 (hd0,2)"...failed (this is not fatal)
Running "install /boot/grub/stage1 (hd0,2) /boot/grub/stage2 p /boot/grub/menu.lst"
...............succeeded
Done
Then after a reboot, Ubuntu was bootable again on my Macbook.
I should mention also that after I created the new partitions with GParted, no icon whatsoever appeared in the rEFIt menu for Ubuntu.
However, after I accepted the Partitioning Tools offer to upgrade the MBR partition table, an icon of sorts (but not Tux) did appear for Ubuntu. However, clicking on this got no further than giving a "Missing operating system" message.
An awful lot of this had already been reported in this
thread by karl_kashofer. So, thanks to him for smoothing the path for me.
Many thanks to pxwpxw for guiding me through this.