ESXi 6.7 won't boot from Windows ISOs

[theaaronmello]

ESXi 6.7 won't boot from WIndows ISOs but WILL boot from Linux ISOs (Ubuntu & CentOS).

I have tried Windows Server 2016 and Windows 10 ISOs - neither will boot but if I burn it to a USB drive it will boot from that and I can install.

Any thoughts as to why Linux ISOs work but Windows don't? One thing I've noticed is that the "Connect" box for the CD/DVD drive unchecks itself each time I boot, but the "connect at power on" stays checked. Even when I recheck the connect box it fails to boot. But if I burn the to USB it works. Any thoughts?

Thanks!

[dariusd]

Have you checked that the .iso files have arrived in your datastore with the correct file-size and SHA1 checksum?  The overwhelming majority of these failures are the result of an .iso file which was truncated during upload.  Internet Explorer was very good at truncating large files like that.  The Windows disc images usually have the EFI boot material at the very end of the disc, so any truncation of the disc image will render the disc unbootable or yield weird error messages about missing drivers early during setup.

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Darius

[theaaronmello]

Thanks for your response. I tried reuploading the ISOs with SFTP and still have the same problem. Stupid question, how do I check the hash checksums?

[bsob]

you can verify using Microsoft File Checksum Integrity Verifier, please change for another bootable iso, this  problem sometimes appears when your iso file is corrupted

[dariusd]

I'd enable the ESXi shell and run:

sha1sum /vmfs/volumes/datastore1/ISOs/Windows\ 10\ Pro\ en-US\ v1909\ x64\ ....iso

It will output a SHA-1 sum 40 hex digits in length.  Go to the page from which you downloaded the .iso file, and it should give the file's expected SHA-1 sum.  They should be identical.

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Darius

[daphnissov]

Agree here with Darius. In addition, verify the hashes on the system which transferred the ISOs to the datastore. This seems to be a clear case of corruption.

[theaaronmello]

Thanks! The SHA checksums are indeed different so looks like you're right. I had thought SFTP would be better than uploading to ESXi in the browser. Any recommendations on better way to upload them? I'm surprised there is so much trouble copying them correctly.

[theaaronmello]

UPDATE:

I copied the ISOs over ethernet instead of wifi and verified the sha1 checksums and file sizes are identical but ESXi still won't boot from them. I have Win10 & Server 2016 ISOs and neither will boot. Both boot from USB if I burn the ISO with Rufus. I suppose I can just use USB drives to set up my VMs but it's less convenient.

Any other ideas? Thanks!

[daphnissov]

Against which checksums did you validate the transferred ISOs? What you had on your local machine, or those published by Microsoft?

[theaaronmello]

I'm comparing them to the checksum values on my local machine. They are not official ISOs from MS so I'm not able to compare them that way but they are bootable and install if burned to USB.

[daphnissov]

They are not official ISOs from MS

So they're like homebrew Windows ISOs you built? If so, don't know what to tell you other than you've done something wonky with the boot sector that causes them to be malformed somehow as an ISO file. Don't know what to tell you other than it's an ISO problem. It's not an ESXi problem as the only time I've ever seen or heard of ISOs not booting is when it's the file itself. You can verify by getting a vanilla ISO from MS of some Windows variety, uploading it, and booting off it.

[dariusd]

Can you please configure a VM to boot from the .iso, power it on, wait for it to fail booting, power it off, and then grab the vmware.log from inside the VM's directory on the datastore, and post it as an attachment here?  (Just look for the Attach link in the lower-right corner when composing your reply.)

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Darius

[DrNoNamh]

<removed by moderator>

I have uploaded thousands of ISO files only using the datastore browser, and never had any problems... except in ESX 5.1 CU2 with a slow encryption... and aaaaaaaaalways via LAN.

And there is another particularity with Windows 10 / 2016, the ISO boot will look for a bootable operating system and will boot this, even if DVD drive is the first boot option.

So it is not possible to boot with default boot settings of the VM's bios, you must first edit the delay for bios to 2 seconds and then hit the F12 key for getting the Bios boot manager, then and only then Windows 10 / server 2016 will boot from ISO, e.g. overwriting the exisitng installation or upgrade it.

[dariusd]

I seem to recall that only the BIOS-based Windows CD/DVD bootloader would check your hard disk for an existing installation and chainload it if it finds one; The EFI bootloader does not care what is on your hard disks.  This is how things were from Win7 through to Win10 – and should be the same today unless things have has changed in the most recent builds of Win10.

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Darius

[theaaronmello]

Thank you Darius, please see attached.