Changing boot from legacy to uefi

[fr.mueller]

Hello together,

i try to change the boot order from legacy to uefi on a vmware esxi that is booting from SAN.

First try, just change the boot order to uefi. Server boots into bios

Second try, change th uefi boot parameter to the following value

Boot Loader Name: BOOTX64.EFI

Boot Loader Path: \EFI\Boot\

Same problem. Boot into bios.

Third try, update esxi while uefi is configured. Booting from cd, updating esxi. booting normal. Same issue. Booting into bios.

What else can i try to configure uefi boot? 

Thanks for any hints

Frank

[Riaan van Niekerk]

hi Frank

1 Which ESXi version?

2 Which server model & CPU? 

3 UCSM (domain connected) or CIMC standalone?

4 Service Profile managed by UCS Manager or UCS Central?

CSCuh13333 No boot item added in F6 boot menu for the new installed esxi OS contains commands to manually boot into ESXi if you boot into UEFI shell. E.g. if this works it may mean an issue with the boot entry. 

If you have not found/followed Troubleshooting Boot From San Installation - Cisco Community yet, please have a look.

[fr.mueller]

ESXi Version8

It is an old B200 M3 that i am using for testing before changing production

UCSM connected but not UCS Central

Frank

[Elliot Dierksen]

I don't think you are going to get an M3 server to boot ESXi 8. I don't think the CPU's are compatible. I know my M5's support ESXi 8. I am trying to remember if M4's support ESXi 8, but I don't recall. I upgrade mine a couple years ago.

[Kirk J]

I would agree with Elliot.

https://knowledge.broadcom.com/external/article/318697/cpu-support-deprecation-and-discontinuat.html lists the E5-2600 series of CPUs that the M3s( https://www.cisco.com/c/dam/en/us/products/collateral/servers-unified-computing/ucs-b-series-blade-servers/B200M3_SpecSheet.pdf ) would have had.

Kirk...

[fr.mueller]

Hello Elliot,

i know that it is not supported. But it is working. you can get an m3 to boot with esx8. But you cannot boot from local disk because the controller is not supported. But we are booting from SAN.

Frank

[Riaan van Niekerk]

I am surprised that you were able to install ESXi 8.0 on an M3 (unless you used some of the options to override the checks as per https://vinfrastructure.it/2025/01/installing-esxi-8-with-an-unsupported-cpu/). ESXi 8.0 is only supported on M5 and up as per the Cisco UCS HCL but I have seen it upgrade on M4. 

Do you have a spare M5 blade? If so, could you associate the M5 with the SP that you upgraded? 

[fr.mueller]

I have a lot of old M3 which i can do some testing on. And yes, The CPU and also the local SCSI Controller are not supported. You are not able to boot from local disks.

I will try some more things out this week.

Frank

[Riaan van Niekerk]

Are you able to test switching from legacy BIOS to UEFI on an M3 before upgrading to ESXi 8.0?

According to Broadcom KB Deprecation of legacy BIOS support in vSphere 

• 1 Switch from Legacy BIOS to UEFI mode while still in the older release."
• ...
• 4 If and only if the system is functioning as expected in UEFI mode, then proceed with upgrading ESXi to the new release.

[fr.mueller]

Hello Riaan,

no. I did not test that. And all my old servers are on 8 now. I have testet serval things this week. But so far i was not able to boot from uefi san. Legacy is still working.

Frank

[Riaan van Niekerk]

Since 8.0 on M3 is an unsupported configuration, why would you want to switch to UEFI? Why not just leave it on Legacy BIOS? 

To give you an example - we have M5 blades running Legacy BIOS. Even though 8.0 is supported on M5, 8.0 only supports UEFI. When changing boot mode from Legacy BIOS to UEFI, (before or after upgrading from 7.0 to 8.0), on some of our M5 blades, vNICs and vHBAs reorder. We did extensive testing and wrote commands to bulk rename the vNICs device in ESXi to the versions that ESXi refreshed, and in the end, due to the work required and our upgrade timelines, decided to stay on Legacy BIOS. (We can always switch to UEFI later, should running in Legacy BIOS mode become a supportability issue).

[fr.mueller]

I just wan´t to know how i have to do it. Because when the day come that i have to change from legacy to uefi and do not know how to do it, it´s bad i guess.

And the new VMware Lifecycle Manager also show that it will be not supported in future releases. Thats in preperation of Version 9.

Therefor, i wan´t to know what steps i have to do to switch to uefi. But it looks like it is not only changing the boot policy.

Frank

[Riaan van Niekerk]

You are doing everything right (based on my experience with UEFI)

1. Just ticking the UEFI option in the boot policy, works 99% of the time.
2. In very rare instances, when (1) does not work, you need to add the UEFI boot parameters (which you tested but no success)

Unfortunately, there are a number of things that work against you

1. You are running M3s which are no longer supported, e.g. limits your ability to get Cisco support even if you had the necessary contracts in place.
2. ESXi 8.0 on M3 & M4 is not supported (even if it may somehow install and run).
3. You upgraded before switching to UEFI (whereas the recommended route is to switch before upgrading). 
4. If you installed ESXi 8.0 U1 and used the allowLegacyCPU=true boot parameter to override checking if the CPU is supported was removed in ESXi 8.0 U2 , e.g. the chances of you getting to install ESXi 9.0 become even more slim, as ESXi 9 will require M6 as a minimum (to be supported, regardless if it installs and runs or not).