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USB Flash Drive Preparation

USB Flash Drives

----- There is now an USB Creator tool from Limetech, for both Windows and macOS that users are encouraged to use. The tool can be found here.

----- Important version note: This document is no longer for WINDOWS users. In general, you should use Unraid Server Installation instead. With the advent of the all-in-one releases (as of v4.6 Final), a make_bootable.bat batch installation file is included, that replaces the use of the syslinux utility in preparing the flash drives for booting Unraid. The instructions below do still work, and are necessary for installing versions of Unraid earlier than v4.6 Final, and for preparing a flash drive on a Mac. And there is still value in the advanced troubleshooting tips below.>

The Unraid Server OS is designed to be installed on, and boot from a USB Flash storage device, 512MB or larger. Use a high quality Flash drive from reputable manufacturers such as:

  • Lexar
  • PNY
  • Samsung
  • Kingston
  • And many more


Windows XP

Step 1 Plug the Flash into your PC and re-format it using Windows (right-click the Flash under My Computer and select Format):

  • For File system, select FAT32
  • For Volume label, enter UNRAID (exactly 6 capital letters)
  • Select Quick Format and click Start
  • For many, the above steps were all that was necessary to format the drive. For others, selecting a file system of FAT or FAT16 was necessary, and others found that formatting it with the HP Flash Formatter Tool was required, or even other steps. If you determine that the Windows formatting did not succeed in creating a bootable USB drive, then see the Advanced tips at the bottom.

Step 2 Download the syslinux tool from the Lime Tech download page, and extract syslinux.exe to a simple directory, for example, c:\, and then run it by clicking on Start / Run. In the dialog box, enter:

c:\syslinux.exe -ma f:

If necessary, change the directory from c:\ to whatever directory you downloaded syslinux to, and change the f: to use whatever drive letter that Windows mounted your Flash on.

The syslinux tool will create a hidden system file named ldlinux.sys on the Flash and make the drive bootable. The latest version and a complete distribution of syslinux is available here.

Step 3 Download the latest Unraid Server, and extract the files from the zip archive to your Flash. When extracting the files, make sure that the option to preserve the folder structure is selected. There is a config folder with initial configuration files, that needs to be correctly extracted. If done correctly, you should see bzroot and bzimage on the flash drive, plus a config folder containing files such as network.cfg and ident.cfg.

Step 4 Click on the Safely Remove Hardware tool tray icon and select your Flash drive to be safely removed.

Windows Vista and Windows 7

Step 1 Plug the Flash into your PC and re-format it using Windows (Right-Click the Flash under Computer and select Format):

  • For File system, leave it as Default
  • For Volume label, enter UNRAID (exactly 6 capital letters)
  • Check the Quick Format box and click Start

If you determine that the Windows formatting did not succeed in creating a bootable USB drive, then see the Advanced tips at the bottom.

Step 2 Download the latest Unraid Server, and extract the files from the zip archive to your Flash.

Step 3 On the Flash drive, Right-Click on make_bootable.bat and select Run as administrator. Press any key to continue.

Step 4 The process takes only a moment to complete. You can then close any open windows and eject the Flash drive.


You'll need to download the following:

  • unetbootin - installs Unraid on your flash drive for you
  • syslinux - a collection of linux tools that will allow you to make the drive bootable
  • Unraid - don't unzip it...

1. Plug in your USB Flash drive and format it using Disk Utility.

  • Open Disk Utility (Applications -> Utilities-> Disk Utility) and choose your device from the list on the left - note: In recent versions of macOS you will need to select View > Show All Devices. Please make sure to read carefully to know when to select "Device" or "Partition"
  • Select Partition
  • Choose Partition Layout: 1 Partition
  • Call it 'UNRAID' (no spaces, all caps)
  • Click Options and make sure Master Boot Record is selected
  • Click Apply and your disk will format

2. Verify the new partition

  • Choose the UNRAID partition from the list on the left
  • Select First Aid and Verify Disk
  • Check the "Show Details" box and get the device path for your disk, ex: /dev/disk2s1
  • Unmount the partition by clicking "Unmount" in the top menu
  • leave Disk Utility open, you'll need it again

3. Make the partition Bootable

  • Open Terminal (Applications -> Utilities -> Terminal)
  • Now you'll need the raw disk device name.. so if your partition device path was /dev/disk2s1, the raw device name is /dev/rdisk2, basically you drop the s1 off the end (that's the partition number) and add in a r before disk
  • Type the following command, substituting <device>{=html} for your raw deivce name ex: /dev/rdisk2 and press enter

fdisk -e ``<device>{=html}

  • At the > prompt type the following and press enter between each

f 1\ write\ exit

Note: if you get an error about the device not being available for writing, ensure you have Unmounted the partition in Disk Utility

  • Unmount the partition again in Disk Utility (the above command will cause it to be remounted)
  • Unzip/tar your syslinux download (you can leave it in the Downloads folder
  • cd to that folder in terminal by typing the following (you may need to change the version number to match your download)

cd ~/Downloads/syslinux-4.05/mbr

  • Install the bootable MBR on your flash drive with the following command (again substituting <device>{=html} for your raw device name)

dd conv=notrunc bs=440 count=1 if=mbr.bin of=``<device>{=html}

4. Install Unraid on your prepared Flash Drive

  • Change the extension of your Unraid download from zip to iso
  • Open unetbootin (it will need your password)
  • Choose Disk Image at the bottom and browse for your Unraid iso
  • Choose the device path for your partition (it's probably already selected)
  • Click OK

Note: if you get an error about overwriting menu.c32, click Yes To All

  • When it finishes, you can eject your USB Flash Drive and put it in your Unraid server and power it up

I Think this would work with Windows, Linux versions also. So if any one has Windows or Linux can you try this and write here if it works there also.

Booting Unraid Server

Safely remove/eject the Flash from your PC and plug it into your server. Power up your server and see if it immediately boots (with some motherboards it will). If it does not boot to the Unraid boot screen that displays a choice of starting Unraid or Memtest, reboot your server and enter the BIOS setup. Navigate to the appropriate screen(s) and select your USB Flash device as the boot device. In some BIOS, the flash drive may show up in the list of hard disks, and you may have to select it there. Save your BIOS settings and try to boot the Flash. Be aware that some motherboards will change the boot order when you add hard drives, and you will have to return to these same BIOS screens to re-select your flash drive.

Note: You may need to check here for more BIOS Setup Tips and Other BIOS Suggestions. For machines with an AMI BIOS, check here. For more general BIOS suggestions on getting a machine to boot the USB flash drive, check here, near the bottom of the page. Also see here

If the Flash will not boot, read over the following tips

Unfortunately, some motherboards and BIOS versions are very picky about the geometry or configuration of the USB flash drive. Some combinations of motherboard, BIOS, and flash drive do not work, or only work after more advanced 'modifications'. The following tips are what users have found to work, in different situations. If one does not work for you, try another.

  • If your flash drive had pre-installed "U3" software, it will need to be removed before you format and install Unraid on it. U3 Un-Install software is available here. A U3 removal tool specific to SanDisk drives can be found here.

  • Some instructions for loading syslinux on your flash drive leave off the "-ma" options of the command. If your flash drive does not have a preloaded master boot record and a partition marked as "active", then it is unlikely to boot unless you use the -ma options.

  • Try formatting the USB drive as FAT instead of FAT32

  • You may need to use the HP formatting tool to make your flash drive bootable on your BIOS. It sets the Cylinders/Heads/Sector geometry of a flash drive to an alternate set of geometry values. The alternate geometry will often will make it possible to use your flash drive as a boot disk when your BIOS does not work with the existing geometry. For more info, see here and here and here.

  • Apparently, there is more than one version of the HP format tool. The version of the HP USB Format Tool that works best has a file name of SP27213.exe. Some have had problems with the version named SP27608.exe. (eg. Sandisk 16GB Cruzer Contour & Amicroe 32GB). HP seems to have removed both from their downloads section of their website, but Google HP SP27213.exe and you should be able to find it easily.

  • If it appears as if the flash drive tries to boot, but hangs while decompressing the bzroot or bzimage files on the flash, it is possible that either the bzroot or bzimage file is corrupt or incomplete. This could happen if you did not safely eject the flash drive, after copying the files to it when it was plugged into your PC. The file would only have been partially written to the flash drive.

  • If it appears as if the flash drive tries to boot, but only gets part way before hanging, you may need to add additional options to your syslinux.cfg file on your flash drive to boot your motherboard.

  • If it appears as if the flash drive gets part way through the boot process but stops when loading bzroot, you may need to use the latest version of syslinux in the downloads folder at Lime-Technology. Use of syslinux version 3.63 in combination with the -ma option was the solution in this thread. (After downloading syslinux, extract syslinux.exe from the zip file.) A number of users upgrading from a v4.2 version to a v4.3 version have found that the new syslinux is necessary, even though their flash drive had worked fine with v4.2.

  • If it appears as if the flash drive gets part way through the boot process but reboots when loading bzroot, one user found that he fixed it be replacing his graphics card with an older (possibly more basic) graphics card. 1

  • A user has created another procedure based on the makebootfat tool. This procedure seems especially useful for newer Intel boards, such as boards based on the P965, P35, and P45 chipsets and their G variants. See this post. It worked when nothing else would, on his Intel P965-based board.

  • Also see this thread (uses a Knoppix installation or Live CD), if you have a board that will only boot from a flash drive as a USB-ZIP drive. Similar instructions, using Ubuntu or similar, can be found here:

  • And last of all, try upgrading the BIOS of your motherboard. A later BIOS may have better support for booting from USB.