Ubuntu Compression and Decompression: Detailed Explanation of the tar Command

In Ubuntu systems, file packaging and decompression are common daily operations, such as backing up files or transferring data. The tar command is the core tool for these tasks—it can “package” multiple files or directories into a single file (called a tar package), and can further reduce file size when combined with compression tools like gzip, bzip2, or xz. This article explains the basic usage of the tar command in the simplest way, making it suitable for beginners new to Linux.

1. Core Function of the `tar` Command¶

The core function of tar is “packaging”, which merges multiple files/directories into a single uncompressed file. If you need to reduce file size, you can compress the tar package using gzip/bzip2/xz, generating formats like .tar.gz/.tar.bz2/.tar.xz.

2. Basic Options and Syntax¶

The basic syntax of the tar command is:

tar [options] [tar_package_name] [files/directories]

Here, [options] are key parameters controlling the operation, [tar_package_name] is the name of the generated package, and [files/directories] are the target files or directories to process.

3. Detailed Explanation of Common Options (with Examples)¶

The following are the most commonly used tar options for beginners, each paired with a simple example:

1. Basic Operation Options¶

Option	Meaning	Scenario Example
`-c`	Create a new tar package (packaging)	Generate an uncompressed tar package
`-x`	Extract files from a tar package	Unpack/extract a tar package
`-t`	List files inside the tar package	Preview the content of the tar package
`-v`	Show detailed process (output files being processed)	Make operations clearer
`-f`	Specify the name of the tar package	Must follow the package name (e.g., `-f my.tar`)

2. Compression Format Options (to be used with `-c`/`-x`)¶

Option	Compression Tool	Generated File Format	Features
`-z`	gzip	`.tar.gz`	Fast compression, suitable for small/medium files
`-j`	bzip2	`.tar.bz2`	Moderate compression ratio, balanced speed
`-J`	xz	`.tar.xz`	Highest compression ratio, suitable for large files

3. Extraction Directory Option¶

Option	Meaning	Scenario Example
`-C`	Specify the target directory for extraction	Avoid extracting files directly to the current directory

4. Common Operation Examples¶

1. Packing Files (Generate an Uncompressed tar Package)¶

Requirement: Package all .txt files in the current directory into files.tar

tar -cvf files.tar *.txt

-c: Create a new package
-v: Show detailed process (e.g., “Packing file1.txt”)
-f files.tar: Specify the output package name as files.tar

After execution, files.tar will be generated in the current directory, with a size equal to the sum of all .txt files (uncompressed).

2. Compressed Packaging (Generate `.tar.gz` File)¶

Requirement: Package .txt files and compress them into files.tar.gz (using gzip)

tar -czvf files.tar.gz *.txt

-z: Call gzip for compression
Other parameters: -c (create), -v (show process), -f files.tar.gz (specify package name)

The generated files.tar.gz will be significantly smaller than the uncompressed files.tar, making it suitable for transmission.

3. Extracting `.tar.gz` Files¶

Requirement: Extract files.tar.gz to the current directory

tar -xzvf files.tar.gz

-x: Extract
-z: Use gzip for decompression
-v: Show extraction process

To specify an extraction directory (e.g., /tmp), add the -C option:

tar -xzvf files.tar.gz -C /tmp

4. Viewing Tar Package Content¶

Requirement: Preview the files inside files.tar.gz

tar -tvf files.tar.gz

-t: View the content of the tar package (without extracting)
The command will list the names, permissions, etc., of all files.

5. Compressing to `.tar.bz2` or `.tar.xz`¶

bzip2 compression (generates .tar.bz2):

  tar -cjvf files.tar.bz2 *.txt

Use -j for decompression:

  tar -xjvf files.tar.bz2

xz compression (generates .tar.xz, highest compression ratio):

  tar -cJvf files.tar.xz *.txt

Use -J for decompression:

  tar -xJvf files.tar.xz

5. Notes¶

Compression Format Must Match Options:
- .tar.gz uses -z; decompress with -xzvf
- .tar.bz2 uses -j; decompress with -xjvf
- .tar.xz uses -J; decompress with -xJvf
-f Option Must Follow Package Name:
Incorrect: tar -cvf my.tar -v ( -v is redundant)
Correct: tar -cvf my.tar file1.txt
Directory Structure Preservation:
When packaging a directory (e.g., tar -cvf docs.tar docs/), the original directory structure will be retained after extraction.

6. Quick Start Summary¶

Packing + Compression (Generate .gz): tar -czvf package_name.tar.gz target_files
Decompress .gz: tar -xzvf package_name.tar.gz
View Tar Package Content: tar -tvf package_name.tar.gz

Mastering these basic operations will suffice for most file packaging and decompression scenarios. For advanced features (e.g., excluding specific files), further explore tar’s advanced options, but these basics are sufficient for beginners.