vSphere ESXi 5.5 – Issues with UEFI BIOS using USB Boot for whiteboxes

Recently I’m setting up a new whitebox to extend my vSphere cluster as I’m running low on memory. After a little researching on vSphere 5.5 whiteboxes, there isn’t a lot of ESXi5.5 whiteboxes around using the latest chipset like Intel Z87. So I went ahead to buy a Intel Haswell processor and Asus Z87-A systemboard. As usual I’ve never expected the onboard Realtek network adapter to be working out of the box without customising the drivers. To save myself the hassle of doing up the customised CD for ESXi, I also bought a couple of Intel Pro 1000 network adapters. Afterwhich, I proceed to install ESXi 5.5 onto the thumb drive.

However when I finished my installation, I could not boot up to the ESX installation via USB Thumb Drive. It keeps rebooting into the UEFI BIOS. I thought I’ve done something wrong on the configuration of the BIOS so I did some troubleshooting. The troubleshooting methods are mentioned below. After a simple research, I’ve realised that from vSphere 5.0 onwards, support for UEFI is added and by default, ESX installs with GPT by default. However, it seems very peculiar that a lot of people are facing problem with UEFI BIOS and booting ESXi from USB thumb drive. Installing ESXi into hard disk is fine though. In the past I do not have any issue with booting off USB thumb drive with older BIOS (non-UEFI). In the end, to resolve this issue is to insert an option to install using MBR instead of GPT in the boot options.

Below are my specifications used for my ESX white box and also the steps I’ve tried for troubleshooting. Hope this will help someone who’s interested to install ESXi 5.5.


My vSphere ESXi 5.5 Whitebox Specifications

  • Intel i7-4770 3.4GHz CPU
  • Asus Z87-A System Board (Realtek 8111GR does not work with out-of-box ESX installation ISO)
  • 4 x 8GB DDR3 Kingston Memory DIMMs
  • Plextor M5 Pro 500GB SSD
  • SAN Disk Extreme I 256GB SSD
  • Seagate Momentus XT 500GB Harddisk
  • Thermaltake Hotswap SATA Enclosure 2.5″
  • 3 x Dual Port Intel 1000Pro PT Network Card PCI-E
  • Western Digital Blue 1TB Hardisk
  • SAN Disk 4GB Cruzer USB Thumb Drive
  • Corsair 500W Power Supply

Troubleshooting methods that I’ve tried

  • Install vSphere ESXi 5.5 using DVDROM and boot from UEFI USB Thumb Drive (unsuccessful with my setup)
  • Install vSphere ESXi 5.5 using DVDROM and boot from USB Thumb Drive (unsuccessful with my setup)
  • Disabling legacy USB support option in BIOS and installing vSphere ESXi 5.5 using DVDROM (unsuccessful with my setup)
  • Install vSphere ESXi 5.5 using DVDROM into SATA Harddisk (Success)
  • Install vSphere ESXi 5.5 using DVDROM with “formatwithmbr” option in boot options during installation (Success)


Steps to install vSphere ESXi 5.5 with “formatwithmbr” option

1. Boot into option menu using vSphere ESXi 5.5 installation media as below. Press Enter


2. Press Shift + O to enter “formatwithmbr” boot option.


3. Your cursor should be at runweasel. Press Space and enter formatwithmbr. Your command line should look like below: (runweasel formatwithmbr)

Press Enter.


4. Install as per usual. Remember to set your BIOS option to boot from USB Thumb Drive and it should be able to boot up to ESXi DCUI.



  1. Namaku Jiro April 13, 2014 10:10 pm  Reply

    Thank you, this solved my problem!

    • Vicardo Ng April 14, 2014 11:10 am  Reply

      You are welcome! Glad it helped you 🙂

  2. David Lewis April 29, 2014 5:59 pm  Reply

    Great blog article that really helped me out.

    • Vicardo Ng April 30, 2014 10:52 am  Reply

      Thanks David. Glad it helped 🙂

  3. Richie Knight June 6, 2014 8:18 am  Reply

    Saved my bacon! Great guide and thanks for putting up!

  4. GC July 14, 2014 12:28 am  Reply

    Actually you didn’t need to resort to installing on a hard disk. The same procedure works for installing onto a USB flashdrive. I created a bootable USB flashdrive using RUFUS and the standard ISO and then installed back to that SAME flashdrive by adding the formatwithmbr option.

  5. Vicardo Ng July 31, 2014 2:59 pm  Reply

    Thanks GC. Yes eventually I did format my usb thumbdrive using the formatwithmbr option. The various scenarios that I’ve tested are for learning and understanding purposes on the impact of UEFI BIOS on the various scenarios. 🙂

  6. loybuckz January 27, 2015 9:22 pm  Reply

    Thank you very much! This worked like a charm!

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