Boot option lost

[cmueller]

I have a UCS C240 M5SX that I have been using for testing our product. 

I had been doing OS installs on it and have been successful for the past couple of months.  

Now when I do an fresh OS install, the boot option is no longer present or available.  I did no changes on the server e

[Kirk J]

Not sure why your previous boot options were lost.

You need to determine what type of boot device you are booting to.

Some devices such as the M.2 raid controller require UEFI mode, or if raid volume OS is being installed to is greater than 2TB, also requires UEFI mode.  Your required boot type (legacy vs UEFI) will determine the specific trouble shooting steps.

If you press F6 (boot menu) during POST, are you presented with any options at all?

Please see https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/c/sw/gui/config/guide/4_2/b_cisco_ucs_c-series_gui_configuration_guide_42/b_Cisco_UCS_C-series_GUI_Configuration_Guide_41_chapter_0100.html#concept_25B0E9CD280540E2ADF8A32D92B60612  for general boot order menu settings.

Kirk...

[cmueller]

My situation is that I do multiple OS installs on the same system over and over. We use this to verify different aspects of our software. I need a clean OS every time.
I have a .img.gz image that I use DD to write the image to disk. I have been using this method for several months without issue.
Then all of the sudden after reimaging the drive, and then rebooting, the OS boot option was not available. In previous installs, after the disk re-imaging was completed and the system was rebooted, in the BIOS Boot options I had an OS option to select.
I went into the BIOS, I am using UEFI mode. I tried to create a new boot option, but there was no path to my drive.
I have reset to factory defaults and tried again with no success.
The BIOS sees my virtual disk, CMIC Storage sees my virtual disk, when reimaging with a Live OS and I run "fdisk -l" and it shows my Virtual Disk with no partitioning scheme, which means the Virtual Disk is newly created and has available space for the image.

[Steven Tardy]

Sounds like your UEFI boot entry in BIOS NVRAM was removed/cleared/something.

https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/ucs-manager/GUI-User-Guides/Server-Mgmt/4-1/b_Cisco_UCS_Manager_Server_Mgmt_Guide_4_1/4-1-trial_chapter_01010.html

In some corner cases, the UEFI boot may not succeed because the UEFI boot manager entry was not saved correctly in the BIOS NVRAM. 
You can use the UEFI shell to enter the UEFI boot manager entry manually.

 Typically the OS installation writes this entry to NVRAM. Simply `dd`'ing an image to disk does NOT write this entry to NVRAM.

There is a decent TAC internal document which details how to add a UEFI entry back. This is the best I could find in a public doc:
https://www.cisco.com/c/en/us/support/docs/servers-unified-computing/integrated-management-controller/214692-troubleshoot-failure-to-boot-os-after-mo.html

This doc might be enough to get your server booting again:
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/c/hw/C240M5/install/C240M5/C240M5_chapter_010.html#id_74481