Convert RZ to TAR Online (Decompressing Rzip Back to Raw Tape-Format Bytes)

Why an RZ File Is Usually a Compressed TAR to Begin With

Rzip, written by Andrew Tridgell (also the author of Samba and rsync) and last updated to version 2.1 in February 2006, compresses exactly one stream — it has no built-in way to hold more than one file's worth of content the way a true archive format does. Because of that single-stream limitation, the standard practice for compressing more than one file with rzip is to bundle everything into a .tar archive first, then run rzip over that combined tar stream, producing a .tar.rz file. Converting RZ back to TAR, in the overwhelming majority of real cases, means reversing that exact sequence: decompressing the rzip layer to reveal the tar archive that was underneath it all along.

TAR itself traces back to Seventh Edition Unix in 1979 and was standardized as USTAR under POSIX.1-1988. Its container format bundles files using a simple, fixed-size scheme: a 512-byte header per file recording the name, size, Unix permissions, ownership, and modification time, immediately followed by the file's raw data padded to the next 512-byte boundary. TAR itself applies no compression at all, which is exactly why rzip's compression pass gets layered on top of it in the first place.

What Rzip's Decompression Actually Restores Byte for Byte

Because rzip's compression is lossless — it uses a long-range matching pass across a window up to 900 MB followed by bzip2, neither of which discards any information — decompressing an .rz file that was built from a tar archive restores that tar archive exactly as it existed before compression, header padding and all. There's no approximation or reconstruction involved the way there sometimes is with lossy formats; the 512-byte blocks, checksums, and file metadata inside the recovered TAR are bit-for-bit identical to what rzip compressed originally.

This matters specifically for anything relying on tar's own checksum field, which each 512-byte header carries to detect corruption in that individual entry — since rzip's compression never touches or reinterprets tar's internal structure, a successfully decompressed .rz file yields a tar archive whose own checksums will validate normally, assuming the original tar was valid before it was ever compressed.

This same relationship explains why rzip is sometimes described as a single-purpose compression pass rather than a true archive format in its own right — it never invented its own container structure for holding files, the way ZIP or RAR did, and instead was always meant to sit on top of an existing archive like tar, adding a compression stage that tar itself never provided.

What Removing Rzip's Compression Layer Gains and What It Costs

• Gain — universal tool support for the result: GNU tar (standard on Linux), BSD tar (standard on macOS), and Windows' own tar.exe all read plain TAR archives with no extra installation, unlike .rz which needs rzip or a compatible tool like PeaZip.
• Gain — direct access to individual files: once decompressed, standard tar commands can list or extract specific entries without needing rzip installed at all.
• Lose — all of rzip's size reduction: a plain TAR is, byte for byte, close to the same size as the original files it bundles, since tar itself applies zero compression; whatever rzip's matching pass and bzip2 stage shrank comes back at full size.
• Lose — protection against bandwidth or storage limits: if the .rz file existed specifically because of a size constraint, reverting to plain TAR reintroduces that same constraint.
• Keep — every byte of Unix metadata: permissions, ownership, and modification times recorded in tar's own header survive the round trip completely intact, since rzip's compression never alters or removes them.
• Keep — symlink and sparse-file handling: whatever symlink targets or sparse-file markers GNU tar recorded in the original archive pass through the compression round trip unchanged, since rzip works on raw bytes without interpreting tar's internal record types at all.

Which Tools Actually Reverse an RZ File Back to Plain TAR

The original rzip binary, GPL-licensed and packaged in Debian and Ubuntu's repositories, handles decompression with a simple rzip -d filename.tar.rz, producing the plain .tar file directly — there's no separate conversion tool needed beyond rzip itself for this half of the process. PeaZip, the free graphical archiver for Windows and Linux, also lists RZ among its supported formats and can extract the tar archive from inside its own interface without requiring the command line.

Once the plain .tar file is recovered, GNU tar, BSD tar, or Windows' tar.exe (shipping since Windows 10 Insider Build 17063 in 2018, built on the open-source libarchive project) can all open, list, and extract it without any further tools. Windows 11's 24H2 update also added native File Explorer support for opening .tar files directly by double-clicking, using that same libarchive foundation.

There's no dedicated Windows binary maintained by the rzip project itself, so the decompression half of this conversion on Windows depends specifically on PeaZip rather than the original author's own software — a genuine gap compared to how thoroughly tar itself is supported across every major operating system today.

On Linux and macOS, rzip's own source builds cleanly with nothing more than a standard C compiler and the bzip2 library it calls into for its second compression stage, so anyone converting an .rz file on a system without a prebuilt rzip package can compile it directly rather than depending on a third-party tool at all.

Real Problems Reported Reversing Rzip Back to a Plain Tar Archive

A recurring complaint involves someone with a .rz file and no rzip installation available, discovering that essentially no mainstream archive tool besides PeaZip can open it at all — a direct consequence of rzip staying a specialist Linux/Unix utility after development effectively stopped in 2006, unlike gzip or bzip2, which achieved far broader adoption into general-purpose archivers.

A second documented issue involves confusing rzip with its actively maintained successor, lrzip (Long Range Zip): the two use incompatible container formats despite the similar name and shared long-range-matching concept, so a file compressed with lrzip cannot be decompressed with the original rzip tool, and attempting it produces an error rather than a valid tar archive.

A third reported pattern involves someone expecting the decompressed TAR to be dramatically smaller than the original files, forgetting that tar itself adds no compression whatsoever — after rzip's layer is removed, the recovered archive returns to being close to the same total size as the files it bundles, plus a small amount of 512-byte header overhead per entry.

RZ-Compressed TAR Compared With the Plain Archive Underneath

Questions About Converting RZ Files Back to Plain TAR

Is an RZ file always a compressed TAR underneath?
Not strictly always, but overwhelmingly in practice — since rzip has no built-in way to hold more than one file, bundling multiple files with tar first and then compressing the result with rzip is the standard, documented approach. A single file can technically be compressed with rzip directly without tar, though that's the less common case in practice.

Will decompressing lose any of the original file permissions?
No. Tar's own header stores Unix permissions, ownership, and modification times, and rzip's compression never alters that data — decompression restores the tar archive exactly as it was before compression.

Why is the resulting TAR file so much bigger than the RZ file was?
Because tar itself applies no compression at all. All of the size reduction came from rzip's matching pass and bzip2 stage, and removing that compression layer returns the archive to close to its original, uncompressed size.

Can I decompress an RZ file without installing rzip?
PeaZip, a free archiver for Windows and Linux, lists RZ among its supported formats and can extract it without the command line. Mainstream tools like 7-Zip and WinRAR have no documented native support for the format.

Does lrzip output decompress the same way as original rzip files?
No. Lrzip is a separate, actively maintained project using an incompatible container format, so a file compressed with lrzip cannot be decompressed with the original rzip tool despite the similar name.

Does the recovered TAR file need any repair after decompression?
No, provided the original .rz file wasn't itself corrupted. Rzip's compression is lossless, so a clean decompression restores the tar archive's headers and file data exactly as they existed before compression.