bzexe

bzexe name [...]

name
    The path to one or more executable files to be compressed. For each specified file, bzexe will replace the original executable with a new self-extracting shell script.

bzexe is a utility that compresses executable files using the bzip2 algorithm and replaces them with self-extracting shell scripts. When one of these new scripts is executed, it first decompresses the original executable into a temporary directory (typically /tmp), then runs it, and finally removes the temporary file. This mechanism allows rarely used or large executables to consume less disk space on the filesystem. It's particularly useful in environments where disk space is at a premium, as it offers a trade-off between disk usage and execution speed, as the decompression process introduces a slight delay before the program starts. It acts as a wrapper, making the compression and decompression process transparent to the user.

Using bzexe comes with several important considerations:
Performance Overhead: Each execution of a compressed program involves decompression, introducing a noticeable delay before the program starts, which can be significant for frequently used tools.
Temporary Space Requirement: Requires available disk space in a temporary directory (e.g., /tmp) for the decompressed executable to reside during its execution.
Permission Loss: The setuid/setgid bits and other special permissions of the original executable are not preserved for the temporary, decompressed file. This makes bzexe unsuitable for executables that rely on these special permissions for their functionality or security.
Debugging Difficulty: Debugging a program compressed with bzexe can be challenging as the actual executable is ephemeral and resides in a temporary location.
Signal Handling Interference: The wrapper script that handles decompression might interfere with complex signal handling within the original executable, leading to unexpected behavior.

When you apply bzexe to an executable, it transforms the original binary into a shell script. This script contains the bzip2-compressed form of the original executable embedded within itself. Upon execution, the script's first action is to decompress this embedded binary data to a unique temporary file, typically in /tmp. It then sets the necessary execute permissions on this temporary file and invokes it. After the program finishes execution, the temporary decompressed file is automatically removed, ensuring clean temporary space usage. This entire process is designed to be transparent to the user, who simply runs the command as usual.

bzexe is primarily intended for system administrators or users who need to save disk space for very large, rarely used executables, or in environments with very limited storage, such as embedded systems or older hardware. For frequently accessed programs, the performance overhead introduced by decompression on every run makes it less desirable. With the declining cost and increasing availability of disk space on modern systems, the practical necessity for tools like bzexe has diminished for general desktop or server use, but it remains a viable option for specialized low-resource scenarios.

bzexe is an integral part of the bzip2 compression suite, which was developed by Julian Seward, primarily gaining prominence in the late 1990s and early 2000s for its excellent compression ratio using the Burrows-Wheeler transform. bzexe itself was conceived as a direct counterpart to gzexe (from the gzip package), offering a similar capability to transparently execute compressed binaries, but leveraging bzip2's superior compression. Its development was driven by the need to optimize disk usage on systems where storage was a more critical resource than CPU cycles, although its niche usage has persisted for specific scenarios like large, infrequently accessed utilities.

bzip2(1), gzexe(1), gzip(1), bzip2recover(1)