Help for the advanced and verification options. Flint writes images to physical drives — read the data-loss warning at the bottom.
Controls how the drive is partitioned when image contents are copied onto it (file-copy mode): GPT for modern UEFI systems, MBR for older BIOS/legacy systems, Auto picks GPT for UEFI targets and MBR otherwise. Raw (DD) writes are byte-for-byte copies of the image and ignore this setting.
Select UEFI for firmware using the EFI boot path, Legacy for BIOS boot, or Auto. This influences the partition scheme and where boot files are placed in file-copy mode. Windows To Go always installs boot files for both (UEFI and BIOS).
FAT32 is the most widely bootable (required by many firmware ESPs) but cannot store files over 4 GB. NTFS supports large files and is required for Windows To Go. exFAT handles large files with fewer restrictions but is not bootable on all machines. The filesystem only matters in file-copy mode; raw writes keep the image's own layout.
Raw (DD) copies the image bytes to the drive exactly as-is — fastest and safest for bootable images. File copy repartitions and formats the drive, then copies the ISO contents onto it. Hybrid ISOs (ISO9660 + bootable MBR) are always written raw so their boot record survives.
Keeps changes between reboots on Linux live sticks. Ubuntu-style images get a casper-rw ext4 image at the drive root and the boot config is patched with the persistent kernel option; Debian-live images get a live/persistence.conf overlay instead. Formatting the ext4 image needs wsl mke2fs or a system mke2fs/makefs; if none is available the image is created but left unformatted — an explicit warning is shown and you must format it as ext4 manually for persistence to work.
Applies a Windows installation ISO to the drive with dism /Apply-Image /Index:1 and installs boot files with bcdboot ... /f ALL so the stick boots as a portable Windows install. Requires NTFS (selected automatically), file-copy mode and elevation; the first edition in the image (index 1) is used. Windows To Go and Persistence are mutually exclusive.
After a raw write, Flint reads the drive back and compares its SHA-256 digest against the image, reporting the offsets of any mismatched regions (up to 20) and the read speed in MB/s. Verification can take as long as the write itself. It is skipped after file-copy writes because the drive is not byte-identical to the image.
Re-reads the drive looking for unreadable sectors. Failed reads are retried up to the configured number of times (1–10, default 3); sectors that never read back are reported at 4 KiB-aligned offsets. If mismatches or unreadable sectors are found, Flint offers to retry the write or abort.
Raw writes are buffered in chunks — 8 MiB by default, configurable from 4–64 MiB in Expert mode. The native writer uses Windows CreateFile/WriteFile with FILE_FLAG_NO_BUFFERING and sector-aligned buffers for the highest throughput. Build it with python setup.py build_ext --inplace (the CI workflow does this before packaging); when it is not built, writes automatically fall back to the pure-Python writer. Toggle it on in Expert mode to use it.
The CI workflow (`.github/workflows/build-windows.yml`) builds flint.exe, computes its SHA-256 checksum (certutil -hashfile dist\flint.exe SHA256) and uploads both as workflow artifacts and release assets on every run. Code signing is optional: set the WINDOWS_SIGNING_PFX (base64-encoded PFX) and WINDOWS_SIGNING_PASSWORD repository secrets and CI imports the certificate, signs with signtool sign /fd SHA256 /a and removes it again. Without the secrets, the build logs a clear "signing skipped" warning and still publishes the unsigned EXE with its checksum. Download signed builds from the releases page.