Talk:Multiboot USB drive

Windows asks to reformat USB stick after generating Hybrid UEFI GPT + BIOS GPT/MBR USB

After following the instructions in Multiboot USB drive#Hybrid UEFI GPT + BIOS GPT/MBR boot, booting into Windows 10 and connecting the multiboot USB, Windows refuses to recognise the partitions on the device and shows an error saying "You need to format the disk in drive E:\ before you can use it.". Perhaps a warning on the wiki entry to notify people that this will happen should be added and/or the instructions in the entry should be changed to prevent this?

Schicko (talk) 13:05, 22 September 2017 (UTC)

What file system have you used for the data partition in the third step? -- Lahwaacz (talk) 07:00, 24 September 2017 (UTC)

Apologies for the late reply. GParted indicates 3 partitions on the flash drive:

• sdb1 is a 1MiB grub2 core.img with flag bios_grub.
• sdb2 is a 500MiB fat32 with flags boot and esp.
• sdb3 is a 14.16GiB fat32 with flag msftdata.

There is also 1MiB unallocated space at the end.

lsblk -fs indicates that sdb2 and sdb3 are both vfat though.

Schicko (talk) 00:12, 28 November 2017 (UTC)

What happens if you remove the msftdata flag? Also according to the section on this page, the boot flag should be on the third partition, not the second. -- Lahwaacz (talk) 09:27, 28 November 2017 (UTC)

GParted automatically re-applies the msftdata flag after removing it and applying the changes. I think it is a default flag that is set automatically when no other flags are set. I also tried your suggestion of having the boot flag on the third partition (along with the esp flag which GParted automatically sets on partitions with the boot flag) instead of the second (which now has the msftdata flag automatically set to it). However, this didn't fix the issue as Windows still doesn't recognise the partitions, but the flash drive does remain bootable.

Schicko (talk) 13:03, 28 November 2017 (UTC)

Isohybrid from the syslinux suite

Am I right that isohybrid from https://www.syslinux.org/wiki/index.php?title=Isohybrid is also capable for the task of preparing a multiboot USB drive? The way I understand it, for bios booting it support up to 4 iso images, where each image is on a separate primary partition. It also state to have a similar application for UEFI.

The bios of one 2006 PC I encountered doesn't recognize as bootable a USB stick that was created for a single small iso image by isohybrid with its default values. That bios can boot another iso image, one that Rufus wrote to another stick.

Regid (talk) 18:14, 1 December 2018 (UTC)

Isohybrid is something different. It refers to a way of preparing .iso images such that you can boot them in two ways:

1. Via burning the image onto an optical drive (e.g. CD-R) and booting from the CD/DVD/whatever. This uses an ElTorito bootloader.
2. Via dd if=my.iso of=/dev/usbstick and booting from the USB stick. This uses another bootloader, from the MBR sector.

By a fortunate coincidence (or maybe a thoughtful design; I don't really know), ISO9660 sort-of ignores the contents of the first 32kiB of its image. That's what allows to cram an MBR (including a partition table and a bootloader such as isolinux) into an ISO image — which then allows to pretend that this .iso is also a bootable HDD/USB image file (without breaking the ElTorito boot!) — which finally allows to just dd the .iso onto a USB stick and forget the army of "LiveUSB creator" crapwares.

This kind of ISO images is called Isohybrid — because, well, they're MBR/ElTorito hybrids. Not all bootable ISOs are Isohybrid — that's why you cannot in general just take any bootable ISO, plop it onto a flashstick with dd and boot from it successfully. You can, however, convert any boot ISO into IsoHybrid: just discard the bootloader it already has, and install the IsoHybrid combo instead. I've done this successfully using xorriso with a bunch of .iso images; this process is well documented.

Finally, in the context of Multiboot USB — Isohybrid is not really useful; you'll have a totally different setup on the USB image, involving a GPT+MBR, a bootloader specifically with GPT capabilities (e.g. GRUB), and probably a selection of .iso files (distros) you'll want to boot from that stick. The USB image itself won't even be ISO, evenless IsoHybrid; the .iso distros you store inside might be IsoHybrid — but it's only useful so much, since you already know the single way you'll boot into them: via the GRUB. I can see one scenario when you'll be happy to have Isohybrid distros on a MultiBoot USB (again, as .iso files on an ext3-or-whatnot partition): when you'd want to take a distro.iso from that Multiboot USB, and dd it straight onto another USB stick. Can you see why IsoHybrid plays well here? If not, try reading again; I apologize in advance for overly complicated sentences.

Hope that helps. --Ulidtko (talk) 15:11, 21 February 2019 (UTC)

Section 1.2.2 Hybrid UEFI GPT + BIOS GPT/MBR boot

Having a hybrid partition table is dangerous but gdisk already warns the user about it:

WARNING! Hybrid MBRs are flaky and dangerous! If you decide not to use one,
just hit the Enter key at the below prompt and your MBR partition table will
be untouched.

Preferring hybrid setup requires some special scenarios, so i guess users already know the consequences. We better keep this because the alternative method works on some systems only. Instead of removing this, you can add a note about alternative suggested method. Partitioning#Tricking_old_BIOS_into_booting_from_GPT Omeringen (talk) 18:23, 9 March 2025 (UTC)

Ventoy security issues

Although Ventoy is really high quality software and imho the option that wins both on features and usability it should certainly be mentioned that there are well-founded concerns that it could be spyware/malware. Garo (talk) 07:59, 7 April 2026 (UTC)

Closing. Your and @Erus Iluvatar edits are enough. — Andrei Korshikov (talk) 20:19, 13 April 2026 (UTC)