ark

ark is a crash-safe archive and compression tool for Linux and OpenBSD. It creates .ark files with integrated Deflate compression, per-member hashes, an index hash, sandboxed operations, and atomic writes via vendored libchevron.

ark is a command-line tool, not a library, and it does not read or write tar, zip, or other existing archive formats.

Features

• Single .ark archive format with built-in Deflate compression
• Per-member and index integrity verification
• Parallel create and extract using fixed 1MB chunks
• Crash-safe archive writes via vendored libchevron
• Mandatory sandboxing: Landlock/seccomp-bpf on Linux, pledge(2) and unveil(2) on OpenBSD
• Standalone recovery reader generation for long-term archive recovery

Requirements

• Linux 5.13+ or OpenBSD 6.4+
• x86_64 or ARM64
• C11 compiler
• make
• No external runtime dependencies beyond libc/pthread
• Vendored libchevron

Linux 5.13 is a hard minimum because Landlock sandboxing is mandatory. On Linux 5.13 through 5.18, extracting archives containing hardlinks is rejected before filesystem side effects because hardlink extraction requires Landlock ABI v2, available from Linux 5.19.

Build

make release

The binary is written to:

build/ark

Install the binary and manual page:

make install

The default prefix is /usr/local. Override it with:

make install PREFIX="$HOME/.local"

Run the test suite:

make test

Quickstart

Create an archive:

ark create archive.ark path

List archive contents:

ark list archive.ark

Verify archive integrity:

ark verify archive.ark

Extract into a directory:

ark extract --output restored archive.ark

Generate a standalone recovery reader:

ark generate-reader recovery.c
cc -O2 recovery.c -o recover

Recovery reader

ark generate-reader writes a self-contained C11 source file that can extract v1 .ark archives without requiring ark itself. The intended preservation workflow is to keep both files together:

archive.ark
recovery.c

If this repository disappears, or if ark is not installed many years later, anyone with a C11 compiler can build the recovery reader and extract the archive:

cc -O2 recovery.c -o recover
./recover archive.ark

The generated file includes a Deflate decompressor, BLAKE3 and SHA-256 implementations, archive read logic, and a minimal extraction program. See ARCHITECTURE.md section 15 for the full recovery model.

Format overview

[Fixed header]       16 bytes
[Member data]        Deflate-compressed 1MB chunks
[Index]              Member metadata, offsets, chunk sizes, hashes
[Footer]             64 bytes, contains index location and hash

All multi-byte fields are little-endian. The index is verified before extraction touches the filesystem. See ARCHITECTURE.md for the full format specification.

Important limitations

• Not compatible with tar, zip, or other archive formats
• No encryption
• No ACL, SELinux context, or extended attribute preservation
• --overwrite is not rollback-safe
• Index metadata is buffered in memory
• Compression is always enabled; there is no store-only mode
• Recovery readers are separate companion files and must be kept with archives

See ARCHITECTURE.md section 17 for the complete limitations list.

Documentation

• man/ark.1 - command reference
• ARCHITECTURE.md - format and implementation specification
• TECH_STACK.md - build and platform requirements
• TESTING.md - validation strategy
• DEVELOPMENT.md - implementation history and milestones
• libchevron - vendored crash-safe write library used by ark

License

ISC License