RemBoot

A UEFI boot menu (BOOTX64.EFI) for a USB stick: put your *.iso files on it, boot from it, pick one, it boots. Works with Linux live/installer ISOs, WinPE (Hiren's, HBCD), and rescue tools. No bootloader install step; the stick just needs the app plus your ISOs.

Requirements

• A 64-bit UEFI machine. Boot the USB from the firmware boot menu (F12 / F9 / Esc).
• Secure Boot: off by default (the app is unsigned). It can be left on with a signed build + a one-time key enrolment — see Secure Boot.
• WinPE ISOs (Hiren's, HBCD) load boot.wim into a RAM disk; give the machine a few GB of free RAM or Windows Boot Manager stops with 0xc0000017.

Create the USB

The Releases page has prebuilt downloads — BOOTX64.EFI and the remboot-usb tool (.exe for Windows, .deb for Debian/Ubuntu, and a raw Linux binary) — or build from source (see Build from source).

Simplest — one FAT32 partition (ISOs under 4 GB)

No script, no partitioning. Format the USB as FAT32 in Explorer, then copy onto it:

• BOOTX64.EFI into \EFI\BOOT\
• your *.iso files in the root
• optionally remboot.conf

That's it — RemBoot reads and boots ISOs straight off the FAT partition. The only limit is FAT32's 4 GB max file size, so this works when every ISO is under 4 GB.

Larger ISOs — add an exFAT partition

Some images (Windows, Hiren's, Ubuntu) are 6–10 GB and don't fit on FAT32, so put those on a second exFAT partition:

#	Filesystem	Contents
1	FAT32 (~512 MB)	\EFI\BOOT\BOOTX64.EFI
2	exFAT (rest)	your *.iso files (+ optional remboot.conf)

RemBoot can't rely on the firmware to read exFAT, so it includes its own reader — you just create the two partitions once (below) and drop ISOs on the exFAT one.

Windows script (does the two-partition layout for you)

1. Build the app (produces dist\EFI\BOOT\BOOTX64.EFI):

   wsl -d Ubuntu -u root -- bash /mnt/c/GitHub/RemBoot/tools/build.sh

2. Find the USB's disk number in an elevated PowerShell:

   Get-Disk

3. Provision it — this erases the whole disk:

   .\tools\make-usb.ps1 -DiskNumber 2-IsoSource "C:\path\to\your\isos"

   Omit -IsoSource to install only the app and copy ISOs later in Explorer.

Cross-platform tool (Linux / macOS / Windows)

remboot-usb provisions a stick on any OS. Download it from Releases (.exe, .deb, or a Linux binary) or build it with cargo build -p remboot-usb, then either use the graphical interface:

remboot-usb gui # opens a local web page: pick the disk, click Create

or the command line:

remboot-usb list # find your USB's id
remboot-usb create --disk /dev/sdb --isos ~/isos # ERASES the disk

--simple makes a single FAT32 stick (ISOs under 4 GB); otherwise it creates the FAT32 + exFAT layout. Run it as Administrator / root so it can write to the disk. On Linux it needs gdisk, dosfstools and exfatprogs; macOS uses diskutil; Windows uses the built-in Storage cmdlets. The GUI is a small self-contained web server built into the binary — no extra runtime.

Manual (diskpart)

Without the script

Elevated diskpart (replace disk N with your USB — wrong number wipes the wrong drive):

list disk
select disk N
clean
convert gpt
create partition efi size=512
format fs=fat32 quick label=REMBOOT
assign letter=S
create partition primary
format fs=exfat quick label=REMBOOT_DATA
assign letter=D
exit

mkdir S:\EFI\BOOT
copy dist\EFI\BOOT\BOOTX64.EFI S:\EFI\BOOT\BOOTX64.EFI
copy remboot.conf.example D:\remboot.conf REM optional
REM copy your *.iso files to D:\

Existing Ventoy stick

Same layout (exFAT data + small FAT boot partition). Back up VTOYEFI\EFI\BOOT\BOOTX64.EFI, replace it with RemBoot's BOOTX64.EFI; your existing ISOs are read directly.

Managing ISOs

Add or remove ISOs by copying files to the exFAT partition — nothing else to do.

Entries are labelled by filename by default. An optional remboot.conf (on the exFAT partition or the FAT boot partition) sets clean names, versions and order — see remboot.conf.example:

ISO: memtest.iso
NAME: MemTest86+
VERSION: 8.10
POSITION: 3

Keys are case-insensitive; #/; are comments; only ISO: is required. Entries with a POSITION come first (ascending), the rest sort alphabetically. The filename is always what boots, so labels never affect booting.

To edit without touching the file: press E on an entry, change name/version/position, ENTER saves (to the boot partition), ESC cancels, ↑↓ switches fields.

Secure Boot

RemBoot can run with Secure Boot on, using the standard signed-shim + MOK chain (the same mechanism Linux distros and Ventoy use). Build the signed layout in WSL:

wsl -d Ubuntu -u root -- bash /mnt/c/GitHub/RemBoot/tools/secureboot.sh

This produces /root/remboot-esp-sb.img with a Microsoft-signed shim as BOOTX64.EFI, MokManager, RemBoot signed with a key generated locally in dist/keys/ (kept private, gitignored), and ENROLL_REMBOOT.cer (the key to enrol). Put those four files on the FAT boot partition instead of the plain BOOTX64.EFI.

The first boot does a one-time key enrolment (shim can't trust RemBoot yet):

1. Verification failed → OK
2. Press any key to perform MOK management → press a key
3. Enroll key from disk → the REMBOOT volume → EFI/BOOT/ENROLL_REMBOOT.cer
4. Continue → Yes → Reboot

After that RemBoot boots with Secure Boot on. ISOs that ship a signed bootloader (Windows, Ubuntu, Fedora, GParted, …) chainload fine under Secure Boot; ISOs with an unsigned bootloader won't — turn Secure Boot off for those (even Ventoy has this limit). Verified in QEMU with SB-enabled OVMF: RemBoot boots after enrolment, and GParted Live chainloads to its GRUB menu.

Build from source

Everything builds through WSL2 Ubuntu (as root): Rust stable + the x86_64-unknown-uefi target, QEMU + OVMF for testing, mtools/exfatprogs for the disk images.

# build the app + a bootable FAT ESP image + dist/ for the USB script
wsl -d Ubuntu -u root -- bash /mnt/c/GitHub/RemBoot/tools/build.sh
# unit tests (pure logic: exFAT, config, menu, easing)
wsl -d Ubuntu -u root -- bash /mnt/c/GitHub/RemBoot/tools/test.sh
# boot in QEMU (REMBOOT_MEM=8192 for heavy WinPE ISOs)
wsl -d Ubuntu -u root -- bash /mnt/c/GitHub/RemBoot/tools/run-qemu.sh scenarios/real.sh

Layout: core/ is UEFI-free, host-testable logic (exFAT reader, remboot.conf parser, menu state, rendering math); efi/ is the UEFI binary (main.rs, vdisk.rs = the virtual-CD that presents an ISO to the firmware and chainloads it, gfx.rs).

How it boots an ISO

RemBoot presents the chosen ISO to the firmware as a virtual CD served on demand (efi/src/vdisk.rs) — read straight from a FAT file, or from the exFAT partition via its own reader (core/src/exfat.rs) since firmware can't mount exFAT. The firmware then mounts it (El Torito + FAT) and RemBoot chainloads the ISO's own \EFI\BOOT\BOOTX64.EFI. Nothing is copied into RAM.

Tested end to end with memtest86+, gparted-live (GRUB → Linux) and Hiren's BootCD PE (Windows):

memtest86+	gparted-live	Hiren's BootCD PE

License

GPL-3.0 (see LICENSE). Bundles JetBrains Mono under the SIL Open Font License (assets/fonts/OFL.txt).