Disk Image Writer


Difficulty	Advanced
Team Size	2-3 people
Time	~30-35 hours
Demo-ready by	Step 5
Prerequisites	Python or C, Linux device files, binary I/O
Built by	Rufus, balenaEtcher, Raspberry Pi Imager, dd

Skills you'll earn: Raw disk I/O, partition tables, ISO/IMG parsing, USB device enumeration, GUI frameworks (Electron/GTK)

Start by writing raw bytes to a file. End with a GUI tool that flashes OS images to USB drives like Rufus.

Step 1: Write raw bytes to a file (~2-3 hours)

Before touching real hardware, understand block-level I/O.

Open a file in binary write mode using low-level I/O (Node.js fs, Python open() with 'rb'/'wb', or C fopen)
Write a known byte pattern (e.g., 512 bytes of 0xAA)
Read it back and verify every byte matches
Measure write speed

You now have: Controlled binary I/O.

Step 2: Detect USB drives (~2-3 hours)

You need to know which devices are available and safe to write to.

List all block devices on the system (/sys/block/ on Linux, diskutil list on macOS)
Filter to removable devices only — never show the system disk
Display: device path, size, label, mounted partitions
Re-scan when a USB is plugged in (poll or use udev events)

You now have: Safe device enumeration.

Step 3: Write an image to a USB drive (~3-4 hours)

The core operation. You are doing what dd does, but with control.

Open the image file and the target block device
Write in chunks (1MB or 4MB blocks)
Report progress: bytes written, percentage, speed, ETA
Flush and sync after completion

You now have: A functional disk writer.

Step 4: Verify the write (~3-4 hours)

A power glitch or bad sector means the USB won't boot.

After writing, read back every block from the device
Compute a checksum (SHA-256) of the written data
Compare against the checksum of the source image
Report pass/fail with the first mismatched offset if it fails

You now have: Write verification.

Step 5: Handle image formats (~3-4 hours)

Not every image is a raw .img. People download .iso, .gz, .xz, .zip.

Detect format from file headers (magic bytes), not extensions
Decompress on the fly while writing — no need to extract first
Support at minimum: raw, gzip, xz, zip-contained images
Show decompressed size for accurate progress

You now have: Multi-format support.

Step 6: Build a GUI (~4-5 hours)

Command-line tools scare people who just want to flash an SD card.

Simple window: select image, select drive, flash button, progress bar
Use Electron or Tauri
Disable the flash button until both image and drive are selected
Show a confirmation dialog with the drive name and size before writing

You now have: A user-friendly disk writer.

Step 7: Partition and format options (~3-4 hours)

Add a "format only" mode: create a partition table and filesystem (FAT32, exFAT, ext4)
Add a "create bootable USB" mode that writes a bootloader (syslinux/GRUB) after flashing
Let the user pick partition scheme: MBR or GPT

Step 8: Cross-platform support (~3-4 hours)

Abstract OS-specific code behind an interface: device listing, raw writes, unmounting
Package for Windows, macOS, Linux
Handle platform quirks: Windows needs admin elevation, macOS needs disk arbitration

Useful Resources

Where to go from here

Persistent storage partition (flash an OS image but keep a data partition)
Multi-boot USB (multiple ISOs on one drive with a boot menu)
Network flashing (PXE boot from the tool)
Checksum database for popular OS images (auto-verify downloads)

Disk Image Writer ​

Step 1: Write raw bytes to a file (~2-3 hours) ​

Step 2: Detect USB drives (~2-3 hours) ​

Step 3: Write an image to a USB drive (~3-4 hours) ​

Step 4: Verify the write (~3-4 hours) ​

Step 5: Handle image formats (~3-4 hours) ​

Step 6: Build a GUI (~4-5 hours) ​

Step 7: Partition and format options (~3-4 hours) ​

Step 8: Cross-platform support (~3-4 hours) ​

Useful Resources ​

Where to go from here ​