I'm trying to create a bootable USB stick for Ubuntu. I am following the Ubuntu tutorial "Create a bootable USB stick on Windows".

When I try to "Write the ISO" using Rufus, I get the following popup when I click "Start":

The image you have selected is an ISOHybrid image. ..."

The message gives me a option (pre-selected):

"Write in IOS image mode (recommended) or 2) write in DD image mode.

The tutorial did not mention this popup and gives no advice on how to continue.

How should I proceed with this pop up?

  • 1
    Rufus may have updated. Some others: help.ubuntu.com/community/Installation/iso2usb & help.ubuntu.com/community/Installation/FromUSBStick & askubuntu.com/questions/1274878/… We are all users like you, so cannot update instructions. You can file a bug report, if desired. Most systems are now UEFI with gpt partitioning, so do not select MBR or BIOS/CSM/legacy modes.
    – oldfred
    Jun 26, 2021 at 22:48
  • This is a user support site, and not a place for bug reports (including documentation). If you look bottom left on that tutorial link you'll have an option to "Report a Bug on this site" which includes the language/terminology used that may match a prior release of rufus and has thus made it unclear for you. That belongs on bug trackers and not here. This site can help you with your issue, it's a user-support site and not a Ubuntu bug tracker
    – guiverc
    Jun 26, 2021 at 23:04
  • @guiverc: This is not a bug, it is one of the Rufus options. The option is offered when persistence is not selected. Please see my answer. Jun 27, 2021 at 8:21
  • @C.S.Cameron the bug reference was to the OPs original question "Please improve installation instructions" .. the "this site" referring to the link on the ubuntu.coms/tutorials link which Nmath resolved
    – guiverc
    Jun 27, 2021 at 8:34

1 Answer 1


Rufus "Write in ISO image mode vs write in DD image mode"

Writing in ISO image mode extracts the image to the FAT32 formatted USB. All files and folders are accessible from Windows or from Linux. A casper-rw partition can be added to make the Live USB persistent.

Writing DD image mode creates an ISO9660 clone of the operating system similar to a Live USB created using Etcher. This partition is read only and cannot be accessed or the contents viewed using Windows. The contents can be viewed using Linux, but can not be modified. Persistence can only be achieved on a boot by boot basis by manually adding the word "persistent" to the menuentry.

If you want a persistent Live USB that can saves changes between sessions choose ISO image mode. If you do not want to save changes between session you can select DD image mode. If you use the persistence slider to specify a volume of persistence for the USB, you will not be given an option to install in DD image mode.


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