Archiving Files

tar is the Tape Archiver, a utility that was created long ago for backing up data to tape drives. Despite its age, it remains one of the most widely used archiving tools in Unix-like systems today.

Key Characteristics

By default, tar does not compress data—it simply bundles multiple files and directories into a single archive file. Compression can be added as an optional step using various compression algorithms.

Basic Operations

The three fundamental operations you’ll perform with tar are:

• Create archives
• Extract archives
• List archive contents

Creating an Archive

To create a basic archive without compression:

tar -cvf my_archive.tar /home

Flags explained:

• -c = create a new archive
• -v = verbose (show progress)
• -f = specify the filename

Listing Archive Contents

To view what’s inside an archive without extracting it:

tar -tvf my_archive.tar

The -t flag lists the contents of the archive.

Extracting an Archive

To extract files from an archive:

tar -xvf my_archive.tar

By default, this extracts to the current directory. To specify a different output location, use the -C option:

tar -xvf my_archive.tar -C /path/to/destination

Adding Compression

While tar bundles files, you can combine it with compression algorithms to reduce file size. Three common options are available:

Compression Examples

Using gzip (fastest):

tar -czvf /tmp/archive.tgz /home/antonis/.config

Using bzip2 (balanced):

tar -cjvf /tmp/archive.tar.bz2 /home/antonis/.config

Using xz (best compression):

tar -cJvf /tmp/archive.tar.xz /home/antonis/.config

Compression Comparison

Here’s a real-world comparison of the different compression methods applied to the same directory:

ls -l /tmp/archive*

As you can see, xz provides the best compression ratio (reducing the size to just 39% of the original), but it takes the longest to process. Choose your compression method based on your priorities: speed vs. file size.

Quick Reference

# Create uncompressed archive
tar -cvf archive.tar /path/to/dir

# Create compressed archives
tar -czvf archive.tar.gz /path/to/dir   # gzip
tar -cjvf archive.tar.bz2 /path/to/dir  # bzip2
tar -cJvf archive.tar.xz /path/to/dir   # xz

# List contents
tar -tvf archive.tar

# Extract to current directory
tar -xvf archive.tar

# Extract to specific directory
tar -xvf archive.tar -C /destination/path

Conclusion

The tar command remains an essential tool for system administrators and users alike. Understanding the trade-offs between different compression algorithms allows you to make informed decisions based on your specific needs—whether you prioritize speed, storage space, or a balance of both.