RAR to TAR Converter

What is RAR to TAR Conversion?

Converting RAR to TAR means moving archive contents from a proprietary container with built in compression to an open Unix container without compression. The files inside the archive remain unchanged, but both the storage format and the archiving philosophy change. RAR is an archive format with built in compression, developed by Eugene Roshal in 1993. It uses PPMd and LZSS, provides 10-30% better compression than ZIP, and supports recovery records. TAR (Tape ARchive) is one of the oldest archive formats, introduced in Unix in 1979. TAR does not perform compression but only joins multiple files into a single stream while preserving their metadata in the POSIX format.

The main reason to convert RAR to TAR is to prepare data for Unix environments. In Linux and macOS, TAR is the native standard: kernels, distributions, source code, and backups are distributed precisely in TAR. This format preserves the full set of file attributes: owner, group, access permissions in octal representation, symbolic and hard links, and special device files. None of these are fully captured by RAR. After conversion to TAR, the data is ready for Unix pipeline processing: you can apply gzip, bzip2, xz, or zstd externally, transfer it through ssh, or mount it through FUSE.

During conversion, the contents of the RAR are fully extracted, after which files are packed into a TAR container with POSIX metadata filled in. The size of the resulting TAR will be substantially larger than the source RAR because TAR itself does not compress data. If compression is required, it is usually applied as a separate step, producing TAR.GZ, TAR.BZ2, or TAR.XZ as combined formats.

Technical Differences Between RAR and TAR Formats

Data Organization Principles

RAR is a combined format: container and compression in one. Each file is individually compressed by the LZSS or PPMd algorithm, or a group of files is joined into a solid block. The RAR header contains recovery information and metadata oriented toward Windows file systems.

TAR is a pure container without compression. Each file is written sequentially as a fixed length header block (512 bytes) and file data padded to the block boundary. The archive has a streaming structure historically tied to writing on magnetic tape, hence the name Tape Archive.

Capability Comparison Table

Archive Size: Real Examples

Size ratios for typical data sets when converting RAR to TAR without subsequent compression:

Understanding this ratio is critical: TAR is convenient for transferring to Unix infrastructure and applying external compression, but on its own it does not save space. To restore an acceptable size, gzip is usually applied after producing the TAR (fast, moderate compression) or xz (slow, maximum compression).

When RAR to TAR Conversion is Necessary

Moving Archives to Linux Environments

Scenarios where TAR is irreplaceable in Unix systems:

• Server deployment - software distributions, configuration packages, and applications often require TAR specifically for deployment through scripts.
• CI/CD systems - GitLab CI, GitHub Actions, Jenkins transfer build artifacts in TAR archives between pipeline stages.
• Backup to NAS and cloud storage - tools like rsync, rclone, restic work more efficiently with TAR streams than with proprietary formats.
• Docker containerization - Docker image layers are stored in TAR format, and the docker save and docker load commands operate on TAR.
• File system snapshots - saving the state of a directory with permissions and owners in Unix is impossible without TAR.

Preserving POSIX Attributes

When metadata is critical and must not be lost:

• Web servers - access permissions for www directories, scripts, and configuration files directly affect the operation of Apache, Nginx, and applications. RAR does not store this information.
• System configurations - files in /etc, systemd scripts, cron tasks have specific owners and access modes without which operation breaks.
• Programs with setuid/setgid bits - executables with special permission bits preserve them only in TAR.
• Home directory archives - a backup of /home must preserve user ownership, otherwise files end up accessible to the wrong people.

Unix Pipeline Processing Chains

TAR fits naturally into scripts and pipelines:

tar cf - directory | ssh remote 'tar xf -'
tar cf - data | gzip | openssl enc -aes-256-cbc > backup.tar.gz.enc

Such constructions are impossible with RAR without third party utilities. Conversion to TAR opens access to Unix flexibility:

• Streaming through ssh - copying large amounts of data without intermediate files.
• Encryption with external tools - openssl, gpg, age work directly with the TAR stream.
• Parallel compression - utilities pigz, pixz, pbzip2 are applied to the TAR stream for speedup on multi core systems.
• Filtering and transformation - the tar utility with --transform allows renaming files on the fly.

Compatibility with Scientific Processing Tools

In the scientific and data processing environment:

• Machine learning platforms - PyTorch and TensorFlow use TAR for packaging datasets (the webdataset format).
• Bioinformatics - SRA Toolkit, BioConductor work with TAR exports of genetic data.
• Scientific publication archives - arXiv, bioRxiv accept article sources in TAR with LaTeX and graphics.
• High performance computing - HPC clusters process input data exclusively in TAR due to compatibility with MPI and Lustre.

Conversion Process: What Happens to the Archive

Transformation Stages

1. Reading the RAR header - the archive structure is analyzed: version (RAR4 or RAR5), file list, compression methods, presence of encryption and recovery records.

2. LZSS/PPMd decompression - archive contents are decoded into the original files. For password protected RAR files, a password is required.

3. Restoring file structure - files are temporarily placed in the original folder hierarchy. Timestamps and basic attributes available in RAR are preserved.

4. Converting attributes to POSIX format - Windows attributes are converted into Unix permissions: read only becomes 0444, a regular file becomes 0644, an executable becomes 0755. By default, the owner is the current user or one specified explicitly.

5. Forming TAR blocks - each file is written as a USTAR or PAX header block (for long names and extended attributes) and a data stream padded with zeros to a 512 byte boundary.

6. Finalizing the TAR archive - two empty 1024 byte blocks signaling the end of the archive are appended to the stream.

What is Preserved and What Changes

Preserved:

• File names and extensions (including Unicode through PAX extensions)
• Full folder and subfolder structure
• File contents (byte for byte)
• Modification timestamps
• Basic file types

Changed:

• Archive size (grows 5-15x for text data)
• Storage method - sequential stream instead of random access
• Attributes - Windows flags are converted into Unix access modes
• Checksums - TAR stores checksums only for headers, not for data

Not transferred:

• RAR recovery records
• Proprietary RAR comments
• RAR encryption (applied separately to TAR through gpg or openssl)
• Real Unix UID and GID (if the original was created in Windows)

Comparing TAR with Other Archive Formats

TAR vs ZIP

ZIP is a universal format with native OS support.

TAR is used in Unix, ZIP on Windows and in mixed environments.

TAR vs CPIO

CPIO (Copy In Out) is another Unix archive format that appeared in System V.

TAR dominates general use, CPIO remains in special niches.

TAR Combined with Compression

TAR is rarely used without compression. Popular combinations:

• TAR.GZ - fast compression, moderate ratio, the de facto standard for source code distribution
• TAR.BZ2 - better compression than gzip, slower
• TAR.XZ - maximum compression through LZMA2, comparable to 7Z efficiency
• TAR.ZST - a modern Facebook alternative combining speed and good compression

The choice depends on the trade off between archive size and processing time.

TAR Compatibility and Support

Operating Systems

TAR has native support in the Unix family and is available on other platforms:

• Linux - the tar utility is part of the base set of any distribution from coreutils or GNU Tar. Extraction with one command tar xf archive.tar.
• macOS - the tar command (BSD variant) has been present since the very first Mac OS X version. Also supported through The Unarchiver, Keka.
• FreeBSD, OpenBSD, NetBSD - built in bsdtar in the base system.
• Windows - starting with Windows 10 build 17063 (2017) the tar command is available in the command line. On older versions, 7-Zip, WinRAR, PeaZip are used.
• iOS and Android - through file managers with archive support: Documents by Readdle, ZArchiver.
• Chrome OS - through the built in Linux subsystem.

Programming Languages

Working with TAR is available through standard libraries in nearly all languages:

This simplifies automation of TAR archive work in scripts and server applications.

Format History

TAR appeared in 1979 in the seventh edition of Unix (Version 7) as a utility for writing to magnetic tape. Since then, the format has gone through several revisions:

• 1979 - the initial version with fixed file names up to 100 characters
• 1988 - the POSIX.1 (USTAR) standard with long name support up to 256 characters
• 2001 - the POSIX.1-2001 (PAX) standard with extended attributes and Unicode
• 2010s - widespread PAX support in modern utilities
• 2020s - integration into cloud platforms as the format for storing image layers

Over 45+ years of existence, TAR remains a fundamental component of the Unix ecosystem.

Limitations and Alternatives

When Converting to TAR is Not Optimal

• Sending a small number of files in a Windows environment - a Windows user recipient gains no benefit from POSIX attributes; ZIP is more convenient.
• Storage without subsequent compression - pure TAR is significantly larger than RAR, no space savings.
• Archives with critical corruption protection - TAR has no recovery records; partial corruption may lose files after the damaged block.

Alternative Scenarios

If universal Unix compatibility is not required:

• RAR to TAR.GZ - compressed Unix archive, saves space and preserves attributes
• RAR to TAR.XZ - maximum compression plus POSIX metadata
• RAR to 7Z - open format with strong compression but without POSIX
• RAR to ZIP - universal compatibility with all operating systems

For tasks of moving data into Unix infrastructure with further processing chains, TAR remains the optimal choice thanks to standard openness and the preservation of the full set of file system metadata.