Compression Utilities (Demo)
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Video Transcription
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>> Hey, Cybrarians.
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>> Welcome back to
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>> the Linux plus course here at Cybrary.
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I'm your instructor Rob Goelz,
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and in today's lesson we are going to
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be covering compression utilities.
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Upon completion of this lesson,
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you're going to be able to understand why
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compression utilities are important.
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Then during the demo today,
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we're going to use common compression utilities
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such as gzip,
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bzip2, xz, and zip.
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Compression and compression utilities are commonly
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used both in backup and in data transfers.
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We've seen this little bit before as well in Module 18,
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we saw that logrotate can handle low compression.
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We saw some gzip compression with tar in the last lesson.
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We're going to see this again later when
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we discuss data transfer.
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Now compression, like its name
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indicates, makes files smaller,
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which means they take up less space to
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backup and they use less bandwidth to transfer.
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The Linux plus exam explicitly
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focuses on four compression utilities.
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They are gzip, bzip2,
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xz, and zip.
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Those are the ones we're going to
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cover in today's lesson.
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The gzip utility was created
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to replace a program called compressing.
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It was created in 1992,
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it achieves a 60- 70 percent compression rate
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and has been the de facto compression utility
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for a really long time.
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You saw when we talked about tar,
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I just only use gz for the most part.
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Tar is very helpful here we can use tar
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with the z option to do
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gz compression like we talked about.
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If you're not using it with tar,
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you can just use gzip to compress the file
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and then gunzip to decompress the files.
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For example, if we want
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to compress a file called file 1,
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we do gzip file 1 that turns it into file 1.gz.
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Then to uncompress or decompress,
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we do guzip file 1.gz,
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then compresses the file back to just file 1.
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Now the bzip2 utility,
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the bzip2 utility was created in 1996
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and it has a higher compression rate
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than gzip, but it takes longer.
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That's because it uses multiple layers of compression
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and algorithms to get that higher level of compression.
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Bzip2 is the command that we use to
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compress bunzip is used to decompress.
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We can see the same examples there.
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Bzip2 file 1,
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creates file 1.bz2,
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then bunzip2, file 1.bz2,
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gets it back to file 1.
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The tar command uses bzip2 as well.
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But with bzip2,
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we have to use a lowercase dash j option
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to do bzip2 compression with tar.
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Now the xz utility is a little bit newer,
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that was developed in 2009.
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Xz has higher compression than either bzip2 or gzip.
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2013 it actually became the default compression algorithm
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that's used for Linux kernel distribution
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that we're using bzip2 before,
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but xz is just much better, so that's what they use now.
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To compress things with xz,
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we just use the xz command.
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Xz file 1 becomes file 1.xz.
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Then to uncompress, we do unxz file1.xz.
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Then if we want to use this with a tar command,
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we can use the capital J option.
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Remember capital J to use xz with tar for compression.
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Lowercase j with tar to be a base of 2 compression.
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Then the final compression utility we'll talk about today
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before we get into our demo is the zip utility.
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Zip utility is different from the others that we've
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covered because it can operate on multiple files.
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The other commands we talked about,
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they just operate on one file
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and they leveraged tar when we
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want to archive a directory of
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files or compress all of them together.
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Files are copied into a folder
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or archive file and then get compressed.
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Then a new zip file is
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placed in that same directory where we did
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the compression and
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the other compression utilities by comparison,
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just replace the file that's being compressed so,
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it turns it into a different file.
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When we're using the zip utility,
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we use the zip command to
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compress and we use unzip to decompress.
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As I said, tar is not needed here.
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But let's take a look at all
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of these with some demo time.
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Here we are in our demo environment
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and we're going to go back to our last lesson.
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We're going to go ahead right away and create an archive.
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We're just going to create an archive,
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a tar archive of files.tar,
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or we'll call it [inaudible] what's called
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files dot.tar. We're going to do that.
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Everything that's in my home directory,
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that ends with a name files,
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a home raw file.
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Starts with file rather.
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Now we can see the size of this file by
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doing ls-alh on files.tar.
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There we go and there we see that that is
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20 K file here that we've created.
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Now what we can do is we can actually
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copy this a few times to make a couple
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of different modifications here, so to speak.
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Let's go ahead and do a copy on files.
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tar, and we'll copy that to files 2.tar.
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We'll also do another copy to files 3.tar.
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These are the ones that we're going to use to do all of
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our different compression work as
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we go through the purposes of this demo.
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First, let's go ahead and do a gzip,
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let's do a gzip on files.tar.
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We're going to do a bzip2 on files 2.tar.
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We'll do a list here,
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xz on files 3.tar.
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Now we can do als- alh on files tar.
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Now, we're going to see as at
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these files have gone notably smaller.
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We started out with a 20k files.tar.
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If you look at the gzip compression,
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we're down to 464 k.
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If we look at the bzip2 compression, we're down to 408.
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If we look at the xz compression,
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we're down to 432.
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Now if we want to uncompress these, we can do this.
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We have to do this by doing gunzip.
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We do gunzip on files.tar.gz.
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If we want to do an uncompressed on a bzp2 file,
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we do bunzip 2 files 2.tar.bz2.
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Then we can do for xz, we do unxz.
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We're going to do this on files
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3.tar.xz, that is uncompressed.
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Now, if we do an ls-alh on all those again,
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we can see that they've all been
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uncompressed and then they're back to 20
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k. Let's last create
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all of the archives
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compress with each compression utility.
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For example, what we could do is create a tgz file
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by doing tar-create zvf.
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Because we're going to use gzip,
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we're going to call this one files.tgz.
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This'll be on anything in the home rob,
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that starts with the word file.
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Now, we can do the same thing,
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but we're going to do instead of 4gzip compression,
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we're going to do it for bzip2.
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We'll call this files 2.bz2 again, we'll do that.
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Now, let's do the same thing,
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but let's do it for x z.
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Remember with xz we have to use
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an uppercase J instead of a lowercase j.
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This will be files 3.xz.
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Now, once again we can do
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an ls- alh on anything that ends,
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it starts with the word files.
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Now, we can see the final file size of these,
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related to how they look when we
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run them through a compression algorithm.
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Files.xz ends up being 3.ok in size.
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We end up having files 2.bz2b 1.7 k.
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>> Then, our tgc file ends up being about 867 bytes.
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>> With that, we've reached the end of this lesson.
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In this lesson we covered
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the importance of compression utilities.
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We talked about how to use
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the most common compression utilities,
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such as gzip, bzip2,
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x z, and zip.
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Thanks so much for being here
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>> and I look forward to seeing you in the next lesson.
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