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<li value="14">We will now look at how we can add different repositories to our '''c7host''' machine.</li><li>As root, issue the following command: <b><code><span style="color:#3366CC;font-size:1.3em;">yum repolist</span></code></b></li><li>Take a few moments to view the contents of the file. Do you see which repositories are used by the '''yum''' command? Write down the repositories in your lab logbook.</li><li>View the following link to see a general listing of repositories:<br>[ [http://wiki.centos.org/AdditionalResources/Repositories Available Repositories for Centos] ].</li><li>To add this repository, issue the command:<br><b><code><span style="color:#3366CC;font-size:1.3em;">wget https://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm</span></code></b></li><li>To enable the repository in yum, issue the following command:<br><b><code><span style="color:#3366CC;font-size:1.3em;">yum install epel-release-7-5.noarch.rpm</span></code></b></li><li>To clean-up the repository list (including downloading new applications in added repositories), issue the command: <b><code><span style="color:#3366CC;font-size:1.3em;">yum clean all</span></code></b></li><li>To verify that you have added the repository, you can issue the command: <b><code><span style="color:#3366CC;font-size:1.3em;">yum repolist</span></code></b></li><li>Unused and unneeded software can present a security risk and ties up disk space needlessly. Find '''at least 4 other packages''' to remove on your c7host machine(for example: '''sound & video''', '''games''', etc) that you're not using on your system. Be careful to ensure that removing those packages does not also remove other software that you do need.</li>

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{{Admon/tip|Bash Shell Scripting Tips:|<br>'''<u>The Here Document</u>'''<br><ul><li>A neat little trick involving a special type of redirection of stdin symbol: '''&lt;&lt;''' that allows input to be redirected to a command from within the command.<br><br> </li><li>Examples:<br><br>''cat &lt;&lt;+<br>This is a test message<br>This is the second line<br>+''<br><br>''mail -s "test message" youremailaddr &lt;&lt;+<br>This is a test message<br>I hope you like it.''<br>+<br><br>''tr [a-z] [A-Z] &lt;&lt;+<br>i like ops235<br>i love scripting.<br>+''<br><br></li></ul>'''<u>Using sed to Manipulate Text</u>'''<ul><li>The Linux command '''sed''' stands for <u>'''S'''</u>treaming <u>'''Ed'''</u>itor which is an effective way to manipulate a text file, output sent from a command, or from within a "here document". This command can manipulate matching text on a variety of criteria (such as '''line number(s)''', '''regular expression match''', etc). Commands can then be used for manipulation such as '''omitting''', '''printing''', '''substituting''', '''adding''', and '''inserting''' text.<br><br></li><li>The sed option '''-n''' suppresses display of text so the print ('''p''') command can be used; otherwise, the text will be displayed (with edits via the sed command instructions).<br><br></li><li>Results of text manipulation with sed can be stored in a variable using command substitution, or redirected to a file. '''NEVER redirect the stdout from a sed command to the same input file (or the input file will be destroyed)!''' <br><br></li><li>Examples<br><br>''sed 's/&#124;/ /g' &lt;&lt;+<br>I&#124;like&#124;weekends!<br>+''<br><br>''sed 's/$/\n/g' &lt;&lt;+<br>This text<br>should be<br>double-spaced!''<br>+<br><br></li></ul>}}

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We will continue with using shell scripts to create a Software Information Report that manipulates output generated by the '''rpm''' command. The '''sed''' and '''awk''' commands are very useful tools in shell scripting to manipulate text. In this lab, we will be using ''sed'' to allow the user to select certain portions from the rpm command (options -qi).

'''Perform the following steps:'''