To avoid using an internal hard drive or SSD to install the VMware ESXi hypervisor on it, you can install VMware ESXi quite easily on a simple USB key.
The only important thing is that the installation of VMware ESXi has a much better chance of success if you plug your USB key into the back of your computer, rather than into an USB port on the front of the case.

In our case, we used a "Kingston DT Elite 3.0" USB 3.0 key plugged into a USB 3.0 port on the back of our computer.
Note that by plugging the same USB key into the front of our computer, the installation of VMware ESXi failed. While the installation was carried out without problem when it was on the back of our computer.

1. Install VMware ESXi on an USB key
2. Datastores detected during VMware ESXi installation
3. VMware ESXi installed on the USB key
4. Erase the USB key

1. Install VMware ESXi on an USB key

Boot your computer / server from the VMware ESXi installation CD.

Once the VMware ESXi 6.7.0 installer appears, press Enter.

The VMware ESXi installer will scan your computer for storage devices (hard drives, SSDs and USB supports).

As expected, the VMware ESXi 6.7.0 installer detects our "Kingston DT Elite 3.0" USB 3.0 key plugged into the back of our computer on a USB 3.0 port.
We select it and press Enter.

VMware ESXi scans your computer again to verify that your system requirements match those required for its installation.

Confirm the selection of the disk (USB key) by pressing Enter again.

Continue configuring the VMware ESXi installation normally.

Then, confirm the installation of VMware ESXi on your USB key by pressing F11.

The installation of VMware ESXi begins.

If the installation is successful, you will see the "Installation Complete" message appear.
Remove the VMware ESXi installation CD from your computer's CD/DVD drive and press Enter to restart your computer.

Note that if your USB key is plugged into the front of your computer, you may see this error :

Plain Text

Operation failed.

This program has encountered an error :
...
Error (see log for more info):
vmkfstools failed with message: b'create fs deviceName:'vmfs/devices/disks/mpx.vmhba...

Upon restart, if your computer's boot order is configured correctly, your computer will boot to your VMware ESXi USB key.

And VMware ESXi will run smoothly.

2. Datastores detected during VMware ESXi installation

Note that when you install VMware ESXi (whether on a hard drive, SSD or USB key), the datastores present on the various storage devices on your computer will be automatically mounted on your new installation of VMware ESXi.
It's therefore normal that several datastores already appear in the web interface of your new VMware ESXi server if you had previously created one on your computer.

However, if you don't want to use them from this installation of VMware ESXi, you can unmount them to "hide" them without deleting them on the affected hard disks.
To do this, select a datastore and click on : Actions -> Unmount.

Then, do the same for the other databstores that you don't want to use.

Once the datastores have been dismounted, click on "Refresh".

As you can see, unmounted datastores still appear in the list, but 3 columns indicate "0 B" (for "0 Bytes").
Which means VMware ESXi no longer uses them.

3. VMware ESXi installed on the USB key

If you go to "Storage -> Devices", you will find your USB key in the list.
By clicking on its name, you will be able to see :

• his type
• his model : DT Elite 3.0
• his path : /vmfs/devices/disks/mpx.vmhba...
• its capacity (size)
• its partition format : gpt indicates that your computer boots in EFI mode on VMware ESXi
• its identifier (UUID)

You will also be able to see the list of partitions created on it :

• EFI System
• Basic Data
• Basic Data
• VMware Diagnostic
• Basic Data
• VMware Diagnostic

A little further down, you will have a graphical version of the partitions present on your VMware ESXi USB key.

4. Erase the USB key

If you ever want to reuse your USB key just to store data on it, you will encounter a problem on Windows.
Indeed, given that this one has several partitions, you will not be able to simply right-click "Format" on it from the file explorer.
If you go through the disk management available on Windows, it's also possible that Windows doesn't allow you to delete all the partitions present on it to recreate one on your entire USB key.
This is particularly the case on versions prior to Windows 10.

To reset it easily, you will have to use the "diskpart" program present in all versions of Windows.
Accept the displayed User Account Control (UAC), and then type the following commands.

List the disks of your computer using the command below and locate the disk number corresponding to your USB key.

Batch

LIST DISK

In our case, we can see that disk 1 is our USB key.

Plain Text

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online           60 GB      0 B
  Disk 1    Online           14 GB    11 GB        *

Select the disk corresponding to your USB key by indicating its number at the end of the command.
Which gives this, in our case.

Batch

SELECT DISK 1

Completely erase your USB drive by typing the command below.
This will delete all partitions (volumes) present on it.

Batch

CLEAN

Create a new primary partition on your USB drive by typing :

Batch

CREATE PARTITION PRIMARY

Format this partition in NTFS (for example) to be able to store files larger than 4 GB.

Batch

FORMAT FS=NTFS QUICK

Plain Text

 0 percent completed
...
 100 percent completed

DiskPart successfully formatted the volume.

Assign a letter to this partition so that it's visible from the file explorer.

Batch

ASSIGN

Close diskpart by typing :

Batch

EXIT

If you right click "Manage" on "This PC" (or "Computer") and go to "Disk Management", you will see that your USB key has been properly reformatted.