yaz

A terminal UI tool for flashing OS images to USB drives. Built with Go and Charm libraries.

Supports Linux and macOS.

Demo

Features

• Flash ISO and raw disk images (.img) to USB drives
• Auto-detect hybrid vs non-hybrid ISOs
• UEFI bootable USB creation (GPT + FAT32)
• Windows 11 support — automatic WIM splitting for >4GB files
• Real-time progress bar with speed and ETA
• Device scanning and selection

Requirements

• Linux: parted, mkfs.vfat (usually pre-installed)
• macOS: diskutil (built-in)
• Windows 11 ISOs: wimlib-imagex for WIM splitting
  • Debian/Ubuntu: sudo apt install wimtools
  • Fedora: sudo dnf install wimlib-utils
  • macOS: brew install wimlib

Installation

Homebrew (macOS/Linux)

brew install ilkin0/tap/yaz

Go

go install github.com/ilkin0/yaz/cmd/yaz@latest

From source

Requires Go 1.25+ and make.

git clone https://github.com/ilkin0/yaz.git
cd yaz
make build
sudo ./bin/yaz

Usage

sudo yaz

Root/sudo is required for device access.

Notes

Win11 USB boot

The problem: Win11 ISOs contain sources/install.wim (often >4GB). UEFI firmware only boots from FAT32, but FAT32 has a 4GB file size limit. So the biggest file in the ISO can't fit on the only bootable filesystem.

Attempt 1 — Dual partition (FAT32 + NTFS): Created a small FAT32 partition for boot files and a large NTFS partition for data. Failed twice:

1. First try: boot files on FAT32, everything else on NTFS → WIN RECOVERY error (BCD couldn't find boot.wim)
2. Second try: everything on FAT32, only >4GB files on NTFS → "Select driver to install" error (Windows PE couldn't find install.wim across partitions)

Root cause: Windows boot chain expects all files on a single volume. No major tool uses dual-partition — it fundamentally doesn't work without a custom UEFI driver.

Why not NTFS? Rufus uses single NTFS + a custom UEFI:NTFS driver (GPLv2 blob) that chainloads from NTFS.

Why not raw-write (dd)? Win11 ISOs are non-hybrid (no embedded partition table). Tools like balenaEtcher and Caligula only do raw writes, so they can't handle Windows ISOs at all.

WIM splitting: Single FAT32 partition. Copy all files normally, then split oversized .wim files into <4GB .swm chunks via wimlib-imagex split. Windows installer reads split SWMs natively. This is the same approach used by WoeUSB and windows2usb. Works with Secure Boot, no binary blobs, maximum compatibility.

ISO types

• Hybrid (Linux distros): has MBR/GPT, can be dd'd or file-copied
• Non-hybrid (Win11): no partition table, must be file-copied with tool-created partitions
• Raw .img (RaspiOS): full partition table, goes through dd path

Platform notes

• wimlib-imagex: wimtools (Debian/Ubuntu), wimlib-utils (Fedora), wimlib (macOS/Homebrew)
• ntfs-3g FUSE is ~2 MB/s write speed — irrelevant now since we use FAT32 only