Feb 21

Boot ESXi from USB Flash drive

In trying to save some money on your home lab, you might consider booting ESXi from a USB Flash drive. I mean, all it really does anyway is load ESXi into RAM, so unless you are planning on using an internal hard drive for something else, why not just drop $6 and get a flash drive instead.

I purchased an ADATA Classic Series C008 8GB USB 2.0 Flash Drive. You can use pretty much any flash drive you want. There is no need to use USB 3.0 flash drives. I chose an 8GB over a 1-4GB because I can store the logs on the empty space of this drive (however, I’m currently storing them on a datastore in my NAS)… You have the option at least.


To create the bootable ESXi drive you will need a few things.

  1. Flash drive
  2. ESXi (your version) .ISO
  3. unetbootin (unetbootin-windows-583.exe) (I have been told that Rufus is fast and easy, similar to unetbootin. If unetbootin does not work for you, give Rufus a shot)


  • Plug your flash drive into the computer
  • run unetbootin
  • in Unetbootin, select ‘DISKIMAGE’
  • make sure ISO is selected in the drop down
  • browse for your installer (should say VMvisor in the name)
  • in TYPE: choose USB DRIVE
  • make sure you have the correct drive selected
  • click OK



  • It will begin creating your bootable image

Once it is complete, you are ready to rock and roll!

  • Place the flash drive in your ESXi host and power on the machine
  • Your host should start booting up the installation


  • As you can see it is loading…


  • And loading….




  • Go ahead and hit ‘ENTER’


  • “Read” the EULA and press ‘F11’


  • As you can see it sees the flash drive (obviously since it just loaded from there). We are going to go ahead and install ESXi over the top of everything. We can do this because the installer is loaded into the RAM and won’t be affected by this. hit ‘ENTER’.



  • After it scans the device it will give you a confirmation box. hit ‘ENTER’



  • Choose your language and hit ‘ENTER’


  • Here you will create your root password. DO NOT FORGET WHAT YOUR PASSWORD IS! Hit ‘ENTER’


  • Once again we will confirm the installation… hit ‘F11’



  • Watch it install. This can take a few minutes…


  • Upon completion your host will need to reboot. hit ‘ENTER’ to reboot.



  • Once your system reboots you will be able to login to the interface and setup your host. F2′ will open the following options. Go to CONFIGURE MANAGEMENT NETWORK



  • Use the SPACEBAR to select (X) the NICs you will be using. hit ‘ENTER’ to save the configuration.


  • Setup your static IP information


  • Add in your DNS servers and a hostname (THE HOSTNAME IS THE NAME FOR THIS ESXi SERVER)



  • Your ESXi Host is ready to go! head over to one of the links shown in the yellow on your host to download the vSphere client and get running!


You should now have an ESXi host that is run off of a USB flash drive and is ready for action in your new VMware environment!






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  1. Itay

    Hi Brian, I came here from Tinkertry.

    First, I’d like to say that you’re doing an awesome work for the enthusiastic community, keep it up!

    As for running ESX from a USB drive – I currently have a very stable ESXi 5.1 host (somewhat resembles one of your builds actually) based on Gigabyte’s GA-Z77X-UD5H which I think is a super motherboard for many.

    When I bought it some good months ago, it came with what I think was a half-baked BIOS. Mainly, complete lack of support for my LSI SAS card and unstable booting from USB devices. It took a while but the manufacturer came up with BIOS updates that addressed most issues.

    I even observed erratic behaviour with bootable USB devices with HP servers at work, hence decided this is not something I’d like to waste time on troubleshooting.

    My “all-in-one-basket” box now runs several VMs from a 240GB SSD and has 7x2TB SATA hard drives assigned to a virtual Nexenta VM (these HDDs are passed-through). Also running is a pfSense virtual router/firewall and WSE2012.

    This keeps me happy, for the time being 🙂

    1. Brian Graf

      Thanks for the comment Itay! It sounds like you’ve got a pretty nice build. so far I haven’t had any issues with my bootable USB devices but I’ve heard of people messing up their bootable USB device when trying to upgrade the version of ESXi they are running on it. I actually was able to confirm the issue but the method that was used wasn’t the most favorable way of upgrading.

      Essentially what I tried in re-creating the user’s problem was pulling the USB drive, trying to wipe it, and then add a ESXi 5.1 as the bootable image (rather than just upgrading the install from the host). The problem was that windows couldn’t remove the partitions created my the initial ESXi install and therefore couldn’t write over the drive. How I fixed this was by downloading a partitioning program (can’t think of which one I used off the top of my head) that was able to go in and unlock the partitions, wipe them, and create one large partition that would then allow unetbootin to create the 5.1 bootable setup.

      I wrote this up quickly at work. Hopefully it made sense 🙂

  2. David

    I am wanting to use the USB to install ESXi 5.1 on a server with no OS installed, can I use this utility(unetbootin) to install ESXi on the server from a USB device?

    1. Brian Graf

      Hi David,

      You can use unetbootin to create the bootable ESXi installer and then when you plug it in to your server you have 2 choices:
      1) you can install ESXi directly onto the flash drive and overwrite the installer itself – essentially turning the flash drive into the O/S
      2) you can use it to install ESXi onto an internal drive on that server so as not to need the flash drive in the future.

      Let me know if you have any other questions. Good Luck!

  3. Gnani

    Hi Brian,

    I’ve installed ESXi 5.1 on an USB, but i cant boot from it in my Dell XPS 15 laptop, But it does work on my mac. The error message it shows on Dell is ” operation system not found ”

    Do you know the reason why, will i have the same problem if i install ESXi on my local hard disk.


    1. Brian Graf

      Hi Gnani,
      Thanks for reading my blog. How did you go about creating the usb flash boot drive? It’s possible it has something to do with how you created it. It sounds to me like it’s actually something to do with your BIOS of the Dell XPS 15. Is it booting UEFI? Not really sure what to tell you if it’s working on your mac and not the xps except check the BIOS…

      You would not have the same issue if you installed ESXi on your local hard disk, however, it should work just fine off of usb. I now have 10 Hosts that all run ESXi off of flash drives. Let me know what you decide to do and how it goes!

      1. Gnani

        Hi Brain,

        I’ve got it working, the problem is with UEFI boot options in the BIOS. In XPS 15 model the advanced boot config option is locked and i assumed that UEFI boot option will be turned on by default (as the options were hidden). I had to flash my Dell BIOS with a custom modded BIOS, I was able to see all the advanced options in my BIOS after flashing. When i enabled the UEFI option the ESXi has booted.

        Thanks for your help. 🙂

      2. MKBELL35

        Are you saying you can boot the 10 host from 10 USB flash drive on one single hardware. i.e ML110 G7 16GB?

        1. Brian Graf

          I’m not sure I understand your question. If you have “one-single hardware” then you would have “one-single host” and only need1 usb drive. If you are planning on running multiple VIRTUAL ESXI hosts, then you would be better off setting up autodeploy on the vCenter Server Appliance and booting the virtual hosts through that.

  4. chris


    I followed the instructions but when I go to boot from the USB it says: “BOOT MGR is missing”.

    Any ideas?

    1. Brian Graf

      Hi Chris,
      Great question. So one of two things has happened. Either you need to adjust a setting in your BIOS (boot order or UEFI) or somewhere along the way the unetbootin messed up. If changing bios settings doesn’t work, try the tutorial over.

      Good luck and let me know how it goes!

      1. Lee

        Try reformatting the USB stick and make sure it is formatted as FAT32. Experienced the same issue the first time I tried and the stick was formatted to NTFS. Reformatted and it worked fine after that.

        Thanks for the info Brian – worked fine once I’d resolved the formatting.

  5. Wenle Z

    what made you choose USB2.0 over USB3.0? I’m afraid putting the ESX5.1 on an USB drive will slow down the whole operation as a whole. Afterall, USB flash drives have really slow seek time and can’t really multithread the read / write. How does your ESXi perform when creating and booting VM? how about changing configurations? does it lag?

    1. Brian Graf

      Thanks for the question Wenle. There really wasn’t any need to go USB3.0 for this. So, what happens is when ESXi boots initially what it is doing is pulling from the flash drive and loading it all into the Host’s RAM. Technically, once it’s booted completely you can technically remove the flash drive from the host and run everything (now doing so will mean that you will lose all changes upon restart obviously, but what i’m saying is your machine runs in RAM and will commit to the flash drive) nothing big is committed. You will not see speed issues and the only difference would most likely be on startup and USB3.0 would probably boot you a few seconds faster. As far as a home lab goes, there is no reason to spend money on the 3.0.

      does that help? let me know if you have any other questions.

  6. xunil-xe

    Hi Brian, really good instructions, going step-by-step on what’s required…, however this went through pretty OK booting on a VM, what happened when I move to the physical host (my PC)?, no network detected 🙁
    I have dig in several websites for the last 3 hours with no joy, my current motherboard it’s a Gigabyte GA-H77M-D3H and I failed to have working the ethernet onboard, and another PCI-E wireless TL-WN881ND same result.

    Any hint will be appreciated!, thanks!

  7. Sal

    It does not work with VMware-VMvisor-Installer-5.1.0.ipdate01-1065491.x86_64.iso, is says missing operating system. Further editing of the menu.cfg might be needed. I’m still looking online for a solution. The USB was formatted FAT32, still doesn’t work.

    1. Sal

      Scratch that. It does work. I had to chase this blog all over the net again to post that it does work and I was wrong. You have to try different USB sticks if/when it doesn’t work. I tried syslinux, rufus, unetbootin, winimage, I don’t even remember what I’ve tried, probably all of them and it still wouldn’t work. I’ve replaced the USB stick with a different one and it worked.

  8. john

    Thanks Brian!

    I followed your instructions step-by-step. Everything worked. I now have my first home brew ESXi host installed and configured.


    1. Brian Graf

      I’m very glad to hear that this has helped you. If you have any other questions about your home lab don’t hesitate to ask. I just started on at VMware as a Technical Marketing Engineer so I will be posting more on the VMware blog but I will start posting more here as well.

  9. NicF

    Brian, thanks for the post, it is very insightful. Now I am wondering about the next step. With a very fast 3.0 USB interface, we can utilize flash drives especially those that are SSD to be able to boot virtual machines from. As I have surfed around the Internet, I’ve come to find out that even though you can boot from USB, and you can pass through a USB device to the virtual machines, you simply cannot connect USB to the ESXi host. So, with a little bit of luck I was able to get the USB drive to stop being arbitrated by the host. I was even able to place a partition manually on the drive. It seems now I am stuck unable to place the file system on the drive. It fails at the very end of placing a VMFS version five filesystem on it. I strongly feel that VMware has overlooked this important feature because in the past a USB drive for a virtual machine was not a good idea due to the slowness of the interface. If you have any insight into this, would you post a blog about it? It would be very helpful for me, and probably the whole community! Thank you!

  10. Michael

    Good day Brian,

    Thank you for your post.
    Do you know by chance of how to confirm/verify that your host does boot from USB rather than local drive? I happened to meet a situation of supporting remotely located host where they were configured with a mix of boot from scenarios. So now I need to be sure to identify what is what.

    1. Brian Graf

      Hi Michael,
      If I understand your question correctly, this is something that would be checked in the bios. If you are using a local disk of sorts, it should be formatted as a datastore (i would assume). When booting up your hosts, you’ll need to change the boot order of the BIOS to boot USB not Hard drive. This will ensure that it boots from your flash drive. Another option you have would be to use autodeploy but you would need to do extra setup and configuration in your lab.

      If these remote hosts have DRAC or IPMI you should be able to login to the host and check the bios settings from there.

      1. Michael

        Thank you Brian,

        I meant that those remote hosts are production and there is no easy way to schedule the reboot to check the bios. My point was of how to identify within OS if it was booted, and set to boot from USB flash. Or at least to check if USB flash is connected to one of its USB ports.

  11. BulkUSB Rep

    Thanks for sharing such a detailed and valueable post . You have very nicley elaborated all the steps for booting ESXi from a USB Flash drive. Great Work!

  12. Jamie

    Hi. Great instructions. I did have to use Rufus however, as UEFI USB thumbdrives, like my SanDisk 16GB would not show up in UNetBootin. I tried formatting and so on, different PCs, but it would never show the thumbdrive as a USB or disk.

    Apparently, and I am only spewing my limited knowledge on this here, the newer USB drives are different than old ones – something about Win 8 (which I do not use myself at home or work). The Rufus program is similar and free – and it saw the thumbdrive and burned the iso very quickly.

    Hope that helps anyone having similar problems 🙂

    1. Brian Graf


      Thanks for the comment and thank you for checking out my blog. I have updated this article and added in a link to Rufus. I appreciate the heads up. Best of luck!

  13. Frank


    For the moment I don’t have an available micro SD card, but in time I’m thinking of getting one, so that I can use the internal USB port for something else. If I choose to install ESXi on the USB key placed in the internal USB port, and later on want to use a micro SD card instead, can I then easily move the installation from the USB key to the micro SD card? What would be the recommended size for the micro SD card?

    1. Brian Graf

      Hi Frank,

      I have not tried copying the files from a USB drive to an SD card. You must also make sure that your server/pc can boot from SD card. If so, a recommended size is up to you. Follow the same principles as using a USB drive. The ESXi files take up only about 300 meg. a 2GB SD card would be sufficient. I went ahead and got 8GB USB drives because I can repurpose them for anything that I want to in the future, and I have ample space for any types of logfiles I decide to save to the drive as well.

      Hope that helps.

      1. Frank

        Sure does. Means that a 2GB card is plenty if I get my hands on suchs (or maybe a 4GB). I don’t see a specific description for micro SD card i BIOS boot options. But there’s for a Floppy Drive (A:) funny enough.

        IPL:1 USB DriveKey (C:)
        IPL:2 Hard Drive C: (See Boot Controller Order)
        IPL:3 PCI Embedded HP Ethernet 1GB 2-Port 332i Adapter Port 1
        IPL:4 CD-ROM
        IPL:5 Floppy Drive (A:)

        Guess booting from micro SD card is not possible.

  14. Flo


    thanks so much for your work. I was able to setup an ESXi 5.0 environment a few months ago. Everything running from an USB drive.

    Now I wonder how I could do an update to ESXi 5.1 or 5.5. Do I loose all my config/settings by using the same or new USB drive? How can I update the existing system without loosing data?

    Thanks in advance.


    1. Shaun

      Flo, you can absolutely do an upgrade to your USB stick. You’ll want to load 5.1 or 5.5 on another stick then boot from it, with your 5.0 stick attached. When the new stick boots, you’ll have the option to upgrade your 5.0 stick. Your configuration will be preserved.

  15. Adam

    Thanks, great post!

    The following is from VMware’s knowledge base:

    “When installing ESXi onto a USB flash drive or SD flash card, if the drive is less that 8GB is space, this prevents the allocation of a scratch partition onto the flash device. VMware recommends using a retail purchased USB flash drive of 16GB or larger so that the “extra” flash cells can prolong the life of the boot media but high quality parts of 4GB or larger are sufficient to hold the extended coredump partition.”

    1. Brian Graf

      Thanks for the informative comment Adam. I will add that into the main post soon.

  16. Ken

    Hi, when the system starts up I get two lines
    command line is empty
    fatal error :32

    Any pointers, trying esxi 5.1

    1. Brian Graf

      Sorry for the delayed reply Ken. I would try 2 things:
      1) Reformat the USB drive and try again
      2) Get a new USB drive

      Only other things that come to mind is to check the BIOS and make sure it’s booting from USB

      1. pmurphs

        I have the same error. Tested USB on another machine and worked fine… I dont think thats the issue.

        Pic of error msg. http://imgur.com/a/sZN3x

  17. Chris


    I have setup my esxi running from USB ad have VMs stored on internal hard drive. All is working perfectly.

    My questions is how do you backup the USB pen drive in case the pen drive fails and I can just stick in another to get back up rand running quickly


  18. Tom

    Hi. Great instructions. I have the server running off the USB on a base Windows 7 machine. I partitioned the disk – allocating space for ESXi storage. Everything is up and running however when attempting to allocate storage my only option is to format the whole disk – utilizing just the partition is not an option. Any ideas?


  19. sateesh

    iam able to install esxi 6 on usb pendrive but not on internal hdd of my laptop. internal hdd is not detecting.

    1. Brian Graf

      This is an issue with the RAID or HD drivers not being compatible. You will need to create your own image (see VMware Image Builder) for more information on how to add the necessary drivers to your ESXi image.

  20. Kevin McGregor

    When booting the VMware ESXi installer, type Shift+O and add “formatwithmbr” after the “runweasel”. The USB drive should then be formatted with MBR instead of GPT and should boot on older machines (which don’t support UEFI/GPT).

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