Does it matter if an OS is listed in GRUB but not available?

Question

I want to create a second OS install on an eSATA disk (Ubuntu to be precise) and create a dualboot with my already existing Windows 7 install. I want use Ubuntu's GRUB bootloader and it should be installed on the permanent drive, since the eSATA disk will not always be attached.

Now obviously, GRUB is going to be needing /boot so I suppose I should create that partition on my permanent drive.

Is there anything else that I need to take into account before undertaking this enterprise? I'd hate to find out I need to repartition everything later on. E.g. will GRUB boot when one or several OS'es are not found?

Answer 1

You can have unbootable entries. GRUB doesn't mind.

Just note, that when some drives are not present, then some other drives may have different ids. For example one disk can be hd1 or hd2 depending if other if present or not.