I have 2 IOs 4506 switches and would like to set them up for DHCP. The idea is to have the one switch's DHCP as a backup for the other.
Is this possible with single supervisors in each switch? I am currently running Sup 5 in each switch.
If your objective is to have 1 switch actively assign addresses and the second switch not assign addresses unless the first switch is not doing it, then this is not possible. If both switches are configured with DHCP then both switches will actively assign addresses.
What you might consider doing is to divide the DHCP scope in half, and configure one half on the first switch and configure the second half on the second switch. This would allow both switches to offer some addresses.
Each switch would respond to a request and the client would decide which offer to accept. It is likely that some clients would wind up accepting offers from the first switch while some other clients would accept offers from the second switch. This would implement the redundancy that seems to be your objective.