How to Create a POSIX Compliant Tar Archive in Ubuntu

This guide explains how to generate tar archives that adhere to POSIX standards using the Ubuntu operating system. It covers the specific command flags required to ensure maximum compatibility across different Unix-like systems and provides a clear example of the syntax needed for compliance.

The Command for POSIX Compliance

To create a tar archive with POSIX compliance on Ubuntu, you must explicitly specify the format using the --format option. The standard command uses the posix format identifier to ensure the archive follows the POSIX.1-2001 standard.

Run the following command in your terminal:

tar --format=posix -cvf archive.tar /path/to/files

Understanding the Flags

• --format=posix: Forces the archive to use the POSIX pax format, ensuring strict compliance.
• -c: Creates a new archive.
• -v: Verbose output, showing files as they are added.
• -f: Specifies the filename of the archive.

Why Use POSIX Format

The default tar format in GNU tar may include extensions that are not recognized by older or non-GNU tar implementations. Using the POSIX format ensures that the archive can be extracted reliably on various operating systems, including macOS, BSD, and other Linux distributions without compatibility issues.

Verifying the Archive Format

You can verify that your archive was created with the correct format by using the --list option combined with verbose output. While tar does not always explicitly state the format during listing, creating a test archive and attempting to extract it on a different system confirms compatibility. For strict validation, rely on the --format=posix flag during creation to guarantee adherence to the standard.