Proxmox VE installer with Multibootusb

This is a mod to allow the Proxmox VE installer to boot using an ISO image copied to /multibootusb/iso/ on a disk created with Multibootusb.

The mod has been created by modifying the initial RAM disk (initrd.img), and, boot files for Proxmox VE 5.4, but, in theory, it should work for all ISOs within the 5.x releases.


You should have Multibootusb installed, and, have a USB stick with Syslinux (or other ISO) created. If you do, you should proceed directly to the Download section of this guide, otherwise follow these steps.

  • Download, and, install Multibootusb.
  • Run the Multibootusb program.
  • Select the correct device for your USB stick.
  • Switch to the Install Syslinux tab.
  • Select Install syslinux and copy all required files.
  • Click Install.

At the end of this process, your USB stick should have multibootusb installed. You should now be able to use the Proxmox-multibootusb mod as intended.








  • Make sure you’ve downloaded the appropriate files:
  • DO NOT rename the ISO file. It has to be in the format proxmox-ve_*.iso.
  • Copy the ISO file to /multibootusb/iso/ (create the directory if it does not exist already).
  • Extract the archive to an empty folder. It should contain the proxmox.d directory. This directory IS the mod.
  • Copy proxmox.d (the directory itself) to /multibootusb/grub/menus/.
  • That should be it for actual installation. See usage below.


  • Boot from the multibootusb drive.
  • Select “Load GRUB2 BootManager”.

  • Select “Scan and boot ISOs under /multibootusb/iso”.

  • In this next screen, select the correct ISO file that you want to boot into.

  • Select “Really boot ‘proxmox-ve_*.iso’?” to load the modded Proxmox grub menu.

  • In the modded menu that appears, select “Install Proxmox VE” (or any other menu item).
  • The mod will scan for the ISO, and, you should see the first page of the installation (the EULA).

What does the mod do?

  • The mod uses a copy of the grub configuration from the Proxmox 5.4 ISO, and, a modded initrd.
  • The grub menus have been tweaked to work with the multibootusb grub menu structure, and, also add a new isopath parameter to the boot options.
  • The modded initrd grabs the new isopath parameter to determine if it should look for an ISO, or, continue like a regular Proxmox installation.
  • With isopath specified, when initrd loads, it scans the drives (irrespective of whether they are removable=1) for the ISO file.
  • Once it finds a drive, that has the isopath, it mounts the ISO to /mnt, and, checks if it is a Proxmox installation ISO.
  • If the ISO check passes, it will proceed with the installation from the ISO image.
  • If the ISO check fails, it will continue scanning the rest of the drives to see if another one has the valid ISO. Eventually (after a couple of retries), if the ISO is NOT found, it will fail like the regular Proxmox installation.