So, you've got a tarball and want to know how to extract it, huh?

Some background info about tar: In the olden days, people primarily used tape devices to store and retrieve data. Tape drives still exist and folks use them to archive data. The name tar is derived from from tape archive. The name of the program that creates and extracts tar files also has the same name - tar. Tarball refers to the archive file. They usually have the extension filename.tar.gz.

Extracting tar files with extension .tar.gz: To extract a tar.gz file use the below command. Assuming you have a tarball by name archived-file.tar.gz:

In the above command the options have the following meaning.

• z - filter the archive through gzip. gzip aka GNU Zip is a program used to compress files. When you use -z option, gzip will be used in tandem with tar.
• x - extract files from an archive. Pretty self explanatory, huh?
• v - verbosely list files processed. The -v option prints information on the screen when the files are being extracted from the archive. If you do not use this option, tar still extracts files silently.
• f - use archive file. This option tells tar to extract from a file. The -f switch is required.

Extracting tar files with extension .tar.bz2: some tarballs are archived using the bz2 compression utility. Assuming you have a tarball by name
archived-file.tar.bz2:

The only difference between the above two commands is the compression program switch. In the above example, we have used the -j option. The -j option instructs tar to use bz2 compression program to extract the files. In our previous example, we used the -z option to instruct tar to use gunzip to decompress the archive.

Extracting tar files with extension .tar: some tarballs may not have any extensions. These type of archives are not compressed at all. It is convenient to transfer a single archived file to a different computer than a bunch of files. You will feel this convenience if you use a FTP client to transfer a set of files to an FTP server. This holds good for downloading too. That is why we have tarballs. Assuming you have a tarball by name
archived-file.tar:

The file extensions are just indicators of the file type. It is not mandatory to use .tar, .tar.gz or .tar.bz2 file extensions to represent respective archive types. If you follow this file naming convention, it will be easier for others to determine the file type just by looking at the name. For argument's sake, let us assume that somebody sent you an archive with the file name archive without any extensions to it. How do you know what command to use to extract the archive? Use the file command to determine the correct file type.

The system reads the file and tells us what type of file it is.

The above command prints the information about the file type. Now we know that the file is bzip2 compressed archive. Do you know what command to use to extract this type of tarball?

You can also view the files in the archive without extracting it.

The above command prints the files contained in the archive file -archive-file.tar.bz2. The -t option instructs tar to list the contents of the archive.

You can also extract selected files from an archive. In the above example, the archive-file.tar.bz2 contains two text files. Let us extract only abc.txt from the archive.

Although the archive contains two files, the above command extracts only abc.txt from archive-file.tar.bz2.

So, you want to know how to create tarballs, huh?

Let us now discuss how you can create tar archives. And compress them too. To create a tarball we will just replace the -x with -c. We know that, -x stands for extract. Similarly, -c stands for create.

For the sake of this example I am assuming that you have two files named abc.txt and xyz.txt. We will use these file names throughout this post. To create a tarball from these two files use the below command:

Alternatively you can use wild cards to achieve the same result instead of typing every file name from which the tarball has to be created.

To use bzip2 compression while creating the archive use the -j option.

To use gzip compression while creating the archive use the -z option.

I use tar to backup my home directory frequently. The path to my home directory is
/home/sudheer. The below tar command creates an archive of all the directories and sub directories under /home/sudheer. To do this you have to change directory to at least one hierarchical level up.

I hope this post is helpful to those of us who are learning compressing and archiving on GNU/Linux. I will look forward for your comments. You can also use the forum to discuss this topic.