I have created an ISO image that contains the Dell firmware.  I did the following:

racadm -r -u -p <*******> set idrac.serverboot.FirstBootDevice VCD-DVD

racadm -r -u -p <*******> set idrac.serverboot.BootOnce Enabled

Mounted the ISO image:

$ vmcli -r -u root -p <********> -c ./R730xd_fw_17R1.iso
Security Alert: Certificate is invalid - self signed certificate
Continuing execution. Use -S option for vmcli to stop execution on certificate-related errors.
Connecting to server....
  Connecting to
. Login success.

Mapping ./R730xd_fw_17R1.iso to Remote Device[0] as Read Only. Success.
................................^[c.......................................................................................................................................

Then I did a powercycle of the server using racadm.

The server rebooted, but it looks like the ISO was never really mounted.

Does the ISO image need to be on an NFS share or something?

I'm on a remote server