rsync re-implemented in Rust. Wire-compatible with upstream rsync 3.4.1 (protocol 32), works as a drop-in replacement.
Binary name: oc-rsync - installs alongside system rsync without conflict.
Release: 0.6.0 (alpha) - Wire-compatible drop-in replacement for rsync 3.4.1 (protocols 28-32).
All transfer modes (local, SSH, daemon), delta algorithm, metadata preservation, incremental recursion, and compression are complete. Interop tested against upstream rsync 3.0.9, 3.1.3, and 3.4.1.
| Component | Status |
|---|---|
| Transfer | Local, SSH, daemon push/pull |
| Delta | Rolling + strong checksums, block matching |
| Metadata | Permissions, timestamps, ownership, ACLs (-A), xattrs (-X) |
| File handling | Sparse, hardlinks, symlinks, devices, FIFOs |
| Deletion | --delete (before/during/after/delay), --delete-excluded |
| Compression | zlib, zstd, lz4 with level control and auto-negotiation |
| Checksums | MD4, MD5, XXH3/XXH128 with SIMD (AVX2, SSE2, NEON) |
| Incremental recursion | Pull direction; sender-side disabled pending interop validation |
| Batch | --write-batch / --read-batch roundtrip |
| Daemon | Negotiation, auth, modules, chroot, syslog, pre/post-xfer exec |
| Filtering | --filter, --exclude, --include, .rsync-filter, --files-from |
| Reference dirs | --compare-dest, --link-dest, --copy-dest |
| Options | --delay-updates, --inplace, --partial, --iconv, fuzzy matching |
| I/O | io_uring (Linux 5.6+), copy_file_range, clonefile (macOS), adaptive buffers |
| Platforms | Linux, macOS (full); Windows (partial - no ACLs/xattrs/symlinks/devices) |
The primary platform is Linux. macOS is well-supported with parity for all metadata, ACL, and xattr features. Windows builds and runs core transfer modes, but several POSIX-specific features are stubbed; ongoing work targets Windows ACL preservation (#1866), Windows xattr (alternate data stream) preservation (#1867), and wiring IOCP into the transfer pipeline (#1868).
| Feature | Linux | macOS | Windows | Notes |
|---|---|---|---|---|
Permissions (-p) |
✓ | ✓ | ⚠ | Windows preserves only the read-only flag; POSIX mode bits are not applicable. |
Times (-t) |
✓ | ✓ | ✓ | Nanosecond precision via the filetime crate on all platforms. |
File ownership (-o/-g, uid/gid) |
✓ | ✓ | ✗ | apply_ownership_from_entry is a no-op on non-Unix; uid/gid mapping is Unix-only. |
ACLs (-A) |
✓ | ✓ | ✗ | Uses exacl on Linux/macOS/FreeBSD; Windows falls through to a no-op stub with a one-time warning (see #1866). |
Extended attributes (-X) |
✓ | ✓ | ✗ | Wired only behind cfg(all(unix, feature = "xattr")); non-Unix uses a no-op stub with a one-time warning (see #1867). |
Hardlinks (-H) |
✓ | ✓ | ✓ | Uses portable std::fs::hard_link; works on NTFS. |
| Symbolic links | ✓ | ✓ | ✗ | create_symlinks is cfg(not(unix)) no-op; symlink entries are skipped on Windows. |
Devices/specials (-D) |
✓ | ✓ | ✗ | create_fifo and create_device_node are no-ops on non-Unix. |
Sparse files (-S) |
✓ | ✓ | ⚠ | Uses portable seek + set_len; depends on filesystem (NTFS supports sparse but is not explicitly marked via FSCTL_SET_SPARSE). |
| Async I/O backend | ✓ io_uring | ⚠ standard I/O | ⚠ IOCP compiled, not wired | io_uring runtime-detected on Linux 5.6+; IOCP is implemented in fast_io but not yet consumed by the transfer pipeline (#1868). |
| Reflink / clone copy | ✓ FICLONE | ✓ clonefile | ⚠ ReFS reflink | Linux Btrfs/XFS/bcachefs via FICLONE; macOS via clonefile; Windows via FSCTL_DUPLICATE_EXTENTS_TO_FILE (ReFS only). |
| Optimized file copy | ✓ copy_file_range |
✓ fcopyfile |
✓ CopyFileExW |
All three are wired into the local-copy executor with standard-I/O fallback. |
Legend: ✓ supported, ⚠ partial or not yet wired, ✗ not implemented.
Compression
- Zstd auto-negotiation - peers exchange supported codecs, first mutual match wins
- Continuous zstd/lz4 stream across files matching upstream session-level codec context
- Per-token compression flush alignment for zlib, zstd, and lz4
Metadata
- ACL wire format (
-A) interop with upstream rsync 3.4.1 - Xattr wire format (
-X) with abbreviation encoding for repeated namespace prefixes - Hardlink receiver-side inode/device mapping for daemon push transfers
Performance
- Adaptive I/O buffers (8KB-1MB) scaled to file size
FileEntrymemory reduced viaBox<FileEntryExtras>for rarely-used fields- Lock-free buffer pool (
crossbeam::ArrayQueue) replacesMutex<Vec> - Shared file list via
Arceliminates per-file clone overhead - Precomputed sort keys remove per-comparison
memrchrcalls - Parallel basis file signature computation in pipeline fill
- Work-stealing deque replaces
par_bridge()for delta dispatch - Rayon-based parallel stat replaces
tokio::spawn_blocking
Batch mode
- Full batch roundtrip with upstream rsync (write + read in both directions)
- INC_RECURSE interleaving, uid/gid name lists, checksum seed in batch header
- Protocol stream format replaces custom encoding
Fixes
- SSH transfer deadlocks and protocol compatibility resolved
- Daemon filter rules applied on receiver side for push transfers
- INC_RECURSE capability direction corrected for daemon push
--files-fromdaemon flag compatibility with upstream- 10+ interop known failures resolved across batch, compression, filters, and paths
Tested against upstream rsync 3.0.9, 3.1.3, and 3.4.1 in CI across protocols 28-32. Both push and pull directions verified for 30+ scenarios covering transfer modes, deletion, compression, metadata, reference dirs, file selection, batch roundtrip, path handling, device nodes, and daemon auth.
Threaded architecture replaces upstream's fork-based pipeline while keeping full protocol compatibility, reducing syscall overhead and context switches. Adaptive I/O buffers scale from 8KB to 1MB based on file size. Optional io_uring on Linux 5.6+ with three policies: auto (default; probe kernel and fall back to standard I/O), --io-uring (require io_uring; error if unavailable), --no-io-uring (always use standard buffered I/O). The active backend is reported by --version and -vv output. See oc-rsync(1) for details.
oc-rsync is wire-compatible with upstream rsync 3.4.1, but a few architectural choices and unfinished surfaces are worth calling out for operators planning a deployment:
- io_uring kernel requirement. Provided buffer rings (PBUF_RING) require Linux 5.19+; older 5.6-5.18 kernels fall back to standard buffered I/O via runtime probing.
- Fixed io_uring buffer pool. The registered buffer pool is sized at compile time (1024 × 4 KiB = 4 MiB) and does not adapt under sustained I/O pressure. Workloads with very high concurrent file fan-out may see throughput plateau before saturating the device.
- bgid namespace. io_uring buffer-group IDs are a 16-bit namespace; the buffer ring helpers cap at this bound. Long-running daemons that recycle thousands of distinct ring groups should monitor for exhaustion.
- Single-thread delta computation. The delta sender is sequential per file. Rolling-hash fan-out across files is not yet parallelised; large-file workloads fully utilise one CPU per transfer rather than scaling delta CPU horizontally.
- SSH compression interaction. When the SSH cipher already performs compression (e.g.,
Compression yesinssh_config), runningoc-rsync -zwill compress payloads twice. There is currently no auto-detection / auto-disable path; operators should pick one layer. - Daemon TLS. Native TLS is not built into the daemon. Deploy
oc-rsync --daemonbehindstunnel,ssh -L, or a reverse proxy that terminates TLS. Seedocs/deployment/daemon-tls.mdfor runnable terminator configs, hardened systemd units, and host-firewall rules; see SECURITY.md for the broader hardening note. - Windows IOCP not wired. IOCP is implemented in
fast_iobut not yet consumed by the transfer pipeline (#1868); Windows uses standard buffered I/O for transfers. .rsync-filterper-directory inheritance. Inheritance semantics match upstream for the common cases tested in the interop suite, but exhaustive parity against upstream's filter-tree corner cases (deeply nested merges, anchored vs unanchored interactions) is still being validated.--checksum-seed/--fuzzy/--iconv. These flags are accepted and exercised in the common path; deeper conformance audits against upstream rsync 3.4.1 are tracked separately.
brew tap oferchen/rsync https://github.com/oferchen/rsync
brew install oferchen/rsync/oc-rsyncDownload from the Releases page:
| Platform | Formats |
|---|---|
| Linux (x86_64, aarch64) | .deb, .rpm (with OpenSSL), static musl .tar.gz |
| macOS (x86_64, aarch64) | .tar.gz |
| Windows (x86_64) | .tar.gz, .zip |
Linux static tarballs are available in two checksum variants:
| Variant | Filename | Description |
|---|---|---|
| Pure Rust (recommended) | *-musl.tar.gz |
Pure-Rust checksums, zero system dependencies |
| OpenSSL | *-musl-openssl.tar.gz |
OpenSSL-accelerated MD4/MD5 checksums (vendored, statically linked) |
Each release also includes three toolchain variants: stable (recommended, no suffix), beta (-beta), and nightly (-nightly).
Requires Rust 1.88+.
git clone https://github.com/oferchen/rsync.git
cd rsync
cargo build --workspace --releaseWorks like rsync - drop-in compatible:
# Local sync
oc-rsync -av ./source/ ./dest/
# Remote pull (SSH)
oc-rsync -av user@host:/remote/path/ ./local/
# Remote push (SSH)
oc-rsync -av ./local/ user@host:/remote/path/
# Daemon pull
oc-rsync -av rsync://host/module/ ./local/
# Daemon push
oc-rsync -av ./local/ rsync://host/module/
# Run as daemon
oc-rsync --daemon --config=/etc/oc-rsyncd/oc-rsyncd.conf
# Delta transfer with compression
oc-rsync -avz --compress-level=3 ./source/ ./dest/
# Checksum-based sync with deletion
oc-rsync -avc --delete ./source/ ./dest/
# Batch mode (record and replay)
oc-rsync -av --write-batch=changes ./source/ ./dest/
oc-rsync -av --read-batch=changes ./other-dest/For supported options: oc-rsync --help
- Rust 1.88.0 (managed via
rust-toolchain.toml) cargo-nextest:cargo install cargo-nextest --locked
cargo fmt --all -- --check
cargo clippy --workspace --all-targets --all-features --no-deps -D warnings
cargo nextest run --workspace --all-featuressrc/bin/oc-rsync.rs # Entry point
crates/cli/ # CLI flags, help, output formatting
crates/core/ # Orchestration facade, session management, config
crates/protocol/ # Wire protocol (v28-32), multiplex framing
crates/transfer/ # Generator, receiver, delta transfer pipeline
crates/engine/ # Local copy executor, sparse writes, temp-file commit
crates/daemon/ # Daemon mode, module access control, systemd
crates/checksums/ # Rolling and strong checksums (MD4, MD5, XXH3, SIMD)
crates/filters/ # Include/exclude pattern engine, .rsync-filter
crates/metadata/ # Permissions, uid/gid, mtime, ACLs, xattrs
crates/platform/ # Platform-specific unsafe code isolation (signals, chroot)
crates/rsync_io/ # SSH stdio, rsync:// TCP transport, handshake
crates/fast_io/ # Platform I/O (io_uring, copy_file_range, sendfile)
crates/compress/ # zstd, lz4, zlib compression codecs
crates/bandwidth/ # Bandwidth limiting and rate control
crates/signature/ # Signature layout and block-size calculations
crates/match/ # Delta matching and block search
crates/flist/ # File list generation and traversal
crates/logging/ # Logging macros and verbosity control
crates/logging-sink/ # Message sink and output formatting
crates/batch/ # Batch file read/write support
crates/branding/ # Binary naming and version metadata
crates/embedding/ # Programmatic entry points for library usage
crates/apple-fs/ # macOS filesystem operations (clonefile, FSEvents)
crates/windows-gnu-eh/ # Windows GNU exception handling shims
crates/test-support/ # Shared test utilities (dev-dependency only)
See cargo doc --workspace --no-deps --open for API documentation.
cli -> core -> engine, daemon, rsync_io, logging
core -> protocol -> checksums, filters, compress, bandwidth -> metadata
-> platform
Key crates: cli (Clap v4), core (orchestration facade), protocol (wire v28-32, multiplex framing), transfer (generator/receiver, delta pipeline), engine (local copy, sparse writes, buffer pool), checksums (MD4/MD5/XXH3, SIMD), daemon (TCP, auth, modules), platform (unsafe code isolation).
All crates enforce #![deny(unsafe_code)]. Unsafe blocks are only permitted in crates that directly wrap platform FFI:
- checksums - SIMD intrinsics (AVX2, SSE2, NEON) with scalar fallbacks
- fast_io - io_uring,
copy_file_range, sendfile, mmap with standard I/O fallbacks - metadata - UID/GID lookup, timestamps, ownership, xattrs, ACLs
- platform - Signal handlers, chroot, daemonize, process management
- engine - Buffer pool atomics, deferred fsync, clonefile
- windows-gnu-eh - Windows GNU exception handling shims
Not vulnerable to known upstream rsync CVEs (CVE-2024-12084 through CVE-2024-12088, CVE-2024-12747). OS-level race conditions (TOCTOU) remain possible at filesystem boundaries.
For security issues, see SECURITY.md.
- Fork and create a feature branch
- Run
cargo fmt,cargo clippy, andcargo nextest run - Open a PR describing behavioral changes and interop impact
GNU GPL v3.0 or later. See LICENSE.
Inspired by rsync by Andrew Tridgell and the Samba team.
Thanks to Pieter for his heroic patience in enduring months of my rsync commentary.
Thanks to Elad for his endless patience hearing rsync protocol commentary as I'm introduced to it.