Working with Compressed Files in Linux

Hands-On Lab

 

Photo of Kenny Armstrong

Kenny Armstrong

Linux Training Architect II in Content

Length

01:00:00

Difficulty

Beginner

Each candidate for the LPIC-1 or CompTIA Linux+ exam needs to understand how to work with various types of compressed files, or "tarballs" as they are commonly known. We will practice with various compression tools, and compare the differences between them.

What are Hands-On Labs?

Hands-On Labs are scenario-based learning environments where learners can practice without consequences. Don't compromise a system or waste money on expensive downloads. Practice real-world skills without the real-world risk, no assembly required.

Working with Compressed Files in Linux

There's a text file named junk.txt in our home directory. It's 133MB and full of random data. We're going to use a few different tools to compress this file, and we'll compare the size differences between each one.

Get the Original File Size

Let's take a look at the original size of junk.txt file and make note of it:

[cloud_user@host]$ ls -lh junk.txt

Creating zip Files

Gzip

First, let's try compressing with Gzip. The following command will compress junk.txt using gzip:

[cloud_user@host]$ gzip junk.txt

Now, run ls to view the size of the file:

[cloud_user@host]$ ls -lh

Notice that the gzip command replaced the original file with a compressed version of it. The other compression commands we use will do the same. Take note of the smaller size of the file, and then decompress it to get the original back:

[cloud_user@host]$ gunzip junk.txt.gz

bzip

Now we're going to perform the same steps, but using the bzip2 compression method instead:

[cloud_user@host]$ bzip2 junk.txt

Note this compression method will take slightly longer than the previous one. Let's check the resulting file size to see how it compared to using gzip:

[cloud_user@host]$ ls -lh junk.txt.bz2

It should be smaller than junk.txt.gz.

Once again, decompress the file to get the original back:

[cloud_user@host]$ bunzip2 junk.txt.bz2

XZ

Now we will try out a newer compression method, XZ. It works with the same syntax as the others:

[cloud_user@host]$ xz junk.txt

Note that this compression will take some time as well. Once the command completes, view your file's size:

[cloud_user@host]$ ls -lh

The resulting file is about the same size as the last one. Now, like we did with the others, let's decompress the file:

[cloud_user@host]$ unxz junk.txt.xz

Creating tar Files

Next, we'll focus on working with tar files. First, we're going to use Gzip to make a tarball:

[cloud_user@host]$ tar -cvzf gztar.tar.gz junk.txt

Then, let's make one using bzip2:

[cloud_user@host]$ tar -cvjf bztar.tar.bz2 junk.txt

Finally, we'll use XZ to make one:

[cloud_user@host]$ tar -cvJf xztar.tar.xz junk.txt

Run the ls command again to compare the file sizes:

[cloud_user@host]$ ls -lh

Notice that creating tar files did not replace the original junk.txt file. Note also how close in size the xz and bzip2 files are to each other.

Practice Reading Compressed Text Files

What if we want to read the contents of compressed files without having to actually decompress them? There is a way! Let's do that now. First, let's copy over the /etc/passwd file to your home directory:

[cloud_user@host]$ cp /etc/passwd /home/cloud_user/

Gzip

We can do the same for a tar file, compressing it with Gzip:

[cloud_user@host]$ tar -cvzf passwd.tar.gz passwd

And we can use the zcat command to read this compressed file:

[cloud_user@host]$ zcat passwd.tar.gz

bzip2

Now let's compress the file, using bzip2, into a tarball:

[cloud_user@host]$ tar -cvjf passwd.tar.bz2 passwd

We can use the bzcat command to read the compressed file:

[cloud_user@host]$ bzcat passwd.tar.bz2

XZ

Finally, let's create an xz tar file:

[cloud_user@host]$ tar -cvJf passwd.tar.xz passwd

And we can use the xzcat command to read its contents:

[cloud_user@host]$ xzcat passwd.tar.xz

Conclusion

You're all set. Congratulations on completing this lab!