Working with Compressed Files in Linux

Note: Please give the lab an extra minute or so before connecting via ssh to allow the lab to fully provision.

Take a look at the original size of your junk.txt file, and make note of it:

ls -lh junk.txt

First, let's try the gzip compression method. The following command will compress the junk.txt file using gzip:

gzip junk.txt

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

ls -lh

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

gunzip junk.txt.gz

Next, perform the same steps, using the bzip2 compression method:

bzip2 junk.txt

Note that this compression method will take slightly longer than the previous. Make a note of the bzip2 file's size (typically, these file sizes are smaller than gzip compressed files):

ls -lh junk.txt.bz2

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

bunzip2 junk.txt.bz2

Now we will try out a newer compression method, using 'xz':

xz junk.txt

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

ls -lh

And finally, decompress the file:

unxz junk.txt.xz

This next set of tasks will focus on working with tar files. First, use the gzip compression method to make a tarball:

tar -cvzf gztar.tar.gz junk.txt

Then, make a new tarball using bzip2:

tar -cvjf bztar.tar.bz2 junk.txt

Lastly, use xz to make a tarball:

tar -cvJf xztar.tar.xz junk.txt

Run the ls command again to compare the file sizes:

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.

The final group of tasks will demonstrate how to read compressed files, without decompressing them on your disk. First, copy over the /etc/passwd file to your home directory:

cp /etc/passwd .

Now, compress the file using bzip2 into a tarball:

tar -cvjf passwd.tar.bz2 passwd

Use the bzcat command to read the bzip2 compressed file:

bzcat passwd.tar.bz2

Do the same for a gzipped tar file:

tar -cvzf passwd.tar.gz passwd

And use the zcat command to read this compressed file:

zcat passwd.tar.gz

And finally, create an xz tar file:

tar -cvJf passwd.tar.xz passwd

And use the xzcat command to read its contents:

xzcat passwd.tar.xz

When done, hand the server over to be graded.