pushfill

Fill a disk with pseudo-random data as fast as possible, then clean up.

pushfill writes pseudo-random bytes to a target directory (or file) until the disk is full or a specified size is reached, then deletes the generated files. It is designed to push out old data from SSDs before recycling or repurposing a drive.

Why?

When you delete files on an SSD, the data isn't immediately erased — the blocks are simply marked as available. Until those blocks are overwritten, the old data remains on the NAND flash. pushfill forces every available block to be overwritten with unique, non-compressible data.

Unlike writing zeroes (which the drive controller might optimise away) or using slow cryptographic wipers, pushfill uses a pool-based random generation strategy with XOR multiplication that produces unique data at maximum speed — typically saturating the drive's write bandwidth.

Features

• Fast — multiprocess workers saturate NVMe drives on Apple Silicon
• Unique data — continuous random generation with XOR multiplication ensures every block is different
• Zero dependencies — pure Python standard library, no pip packages needed
• Cross-platform — works on macOS, Linux, and Windows
• FAT32 aware — auto-detects FAT32 filesystems and respects the 4 GiB file limit
• Live display — colourful terminal UI showing speed, progress, and ETA
• Clean shutdown — Ctrl+C stops gracefully and cleans up generated files

Quick Start

# Install
uv tool install pushfill

# Fill current directory until disk is full, then delete
pushfill

# Fill /tmp with 10 GB of data
pushfill /tmp --size 10G

# Fill and keep the files
pushfill /tmp --size 500M --keep

See Installation and Usage for more details.

---

pushfill is created by WaterJuice and released into the public domain under the Unlicense.