We have seen issue where UCS while booting up it stuck in Shell> prompt.when Cisco Sends Bare metal UCS server loaded with VSM application, It sometimes gets it stuck in SHELL>(Prompt) which will not let you boot from the
PCI RAID adapter however in order to boot the server from PCI adapter i.e. HDD you need type “EXIT” .

SHELL> Exit (Enter) it will load the VSM application and take you to the bash prompt of VSM. Due to this it causes a problem where VSM application does not load by default when there is any power outage or system restart. In that case you have to manually take console or through CIMC (KVM).
Solution: You need to verify what boot priority is set on the server. Either you can check through CIMC or directly taking console of the server. Here we can see the Actual boot order is “HDD then FDD and so on. But if you facing an issue where server falls into the SHELL> prompt you will see first boot order shall be Internal EFI shell which you need to change the boot order from bios.
Here Is the snippet of desired boot order however we won’t be able to change this from CIMC

Step to change the boot sequence
- Restart the server
- Press F2 key to enter boot menu

- Go to “boot options” using right arrow key

- Change the boot order by going to Boot option #1 or any other according to requirement.
- Press enter and select the required boot option.

- Here is the option to change the boot priority.

- Press F10 to save the configuration, system will reboot to save the changes.

for more detail on Unified Extensible Firmware Interface (EFI)
http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/sw/gui/config/guide/2-2/b_UCSM_GUI_Configuration_Guide_2_2/b_UCSM_GUI_Configuration_Guide_2_2_chapter_011111.html#concept_8DDEC0F7A07F4B88A8E714B82838E7F3
Br,
Nadeem ahmed