Command to Display Bzip2 File Header Information Ubuntu

This article explains how to inspect header information for bzip2 compressed files on the Ubuntu operating system. Unlike gzip, bzip2 does not store metadata such as original filenames or timestamps within its header. You will learn the specific commands used to verify file integrity, view block size settings, and examine raw header bytes directly from the terminal.

Using the File Command

The most direct way to read the header signature and basic configuration of a bzip2 file is the file command. This utility reads the magic numbers at the beginning of the file to identify its type and compression settings.

Run the following command in your terminal:

file filename.bz2

The output will confirm the file type and display the block size used during compression, such as bzip2 compressed data, block size = 900k. This information is derived directly from the file header.

Using Bzip2 Verbose Test

To view detailed structural information about the compressed blocks within the file, use the bzip2 utility in verbose test mode. This does not decompress the file but reads through the header and block structures to verify integrity.

Execute this command:

bzip2 -tvv filename.bz2

The -t flag tests integrity, while the -vv flags enable verbose output. The terminal will display details for each block, including start and end positions, bytes used, and CRC checks. This provides the deepest level of internal header information available without third-party tools.

Viewing Raw Header Bytes

For low-level inspection of the header bytes, you can use hexdump. The bzip2 format starts with the magic characters BZ. This method is useful for scripting or forensic analysis.

Run the following command to see the first few lines of hex data:

hexdump -C filename.bz2 | head

The first line of output will show the ASCII representation of the header, confirming the BZ signature followed by the compression version. This confirms the file header is intact at the binary level.