Obtaining a device/partition list

[Hal Wine]

Given a number of commands in the Grub shell, which require specifying 
devices or partitions, I expect to find a couple of commands for 
displaying devices and partitions, but I don't.

except by trial and error, is there any way to find a list of the 
currently active devices?

How about for partitions on a drive?

If there aren't those commands, can someone recommend a "how to" on 
figuring out which bios device is which (especially for scsi chains off 
multiple scsi cards -- how are they ordered).

Thanks,
--Hal

P.S. the primary context is (a) using grub as a mini rescue disk, and 
(b) talking someone through grub changes over the phone.