OPS235 Lab 5 - CentOS6

Archiving Files, Compiling Software Packages from Source, Managing Services

Overview

• In this lab, you are going to help conserve disk space by learning how to compress and decompress files that are stored on your computer server. In addition, you will learn alternative methods of how to install programs (decompressing zipped tarball archives and then compiling source code).

• In addition, you will learn about how certain processes (services) work, and how the system administrator can manage these services (i.e. turn "on" and "off").

Objectives

1. To create and use archive files (tar and tar.gz)
2. Compiling software packages from source code
3. Install an application from software development repositories using the bit utility
4. Customising file-system start-up

Required Materials (Bring to All Labs)

• CentOS 6.5 x86_64 Live DVD
• CentOS 6.5 x86_64 Installation DVD1
• SATA Hard Disk (in removable disk tray)
• USB Memory Stick
• Lab Logbook

Prerequisites

• Completion and Instructor "Sign-off" of Lab 4: OPS235 Lab 4 - CentOS6

Linux Command Online Reference

Each Link below displays online manpages for each command (via http://linuxmanpages.com):

Archiving Utilities:	Service Management Utilities:
tar gzip gunzipzip make	chkconfig

Resources on the web

Additional links to tutorials and HOWTOs:

• archiving with tar, gzip, gunzip
• init vs systemd
• init vs systemd vs upstart
• Runlevels

Archiving Files / Compiling Software from Source Code

Archive files are often used to contain source code for software; in this lab you will also be compiling software from a source code archive.

Do not Shut-Down VMs Until Instructed
You will be running all 3 VMs eventually when performing this tutorial, Leave all VMs running until you are instructed to shut them down at the end of this lab.

Investigation 1: How do you create an archive file?

Use centos3
Perform these steps in the centos3 virtual machine.

1. Boot up your centos3 VM.
2. Change your working directory to /usr/share/doc/sudo*
3. Use the tar (tape archiver) command to create an archive file named /tmp/archive1.tar
   • tar cvf /tmp/archive1.tar .

Warning!
Don't miss the . at the end of the tar commands below! It specifies what should go into the archive: the contents of the current directory.

4. What do the options c, v, and f mean?
5. Record the archive file size.
6. Compress the file using gzip:
   • gzip /tmp/archive1.tar
7. Record the archive file size after compression.
8. Make sure you're still in /usr/share/doc/sudo* and then create a compressed archive:
   • tar cvzf /tmp/archive2.tgz .
9. What does the z option do?
10. Compare the sizes of /tmp/archive1.tar.gz and /tmp/archive2.tgz. Why are they so close in size?

Answer the Investigation 1 observations / questions in your lab log book.

Investigation 2: How do you restore files from an archive?

Remain in your centos3 VM
Perform these steps in the centos3 virtual machine.

1. Create the directory /tmp/extract1
2. Change to the /tmp/extract1 directory.
3. Move the file archive1.tar.gz to your current directory.
4. Unzip the first archive you created:
   • gunzip archive1.tar.gz
5. Extract the files from the first archive:
   • tar xvf archive1.tar
6. Are all the files there?
7. Compare /tmp/extract1/README and /usr/share/doc/sudo*/README. Are they exactly the same? Why?
8. Create the directory /tmp/extract2
9. Move the file archive2.tgz to the /tmp/extract2 directory.
10. Extract the files from the second archive:
    • tar xvzf /tmp/extract2/archive2.tgz
11. Note that this time a separate gunzip command was not needed. Why?
12. Repeat the previous command, leaving out the option "z". Does it work? Why?
13. Compare the README file in this directory with the original file. Are they exactly the same?

Answer the Investigation 2 observations / questions in your lab log book.

Investigation 3: How do you build software from source code?

Now that you know how to create and decompress "zipped tarball archives", we will demonstrate how to install applications from websites containing these types of archives. Although this method is not as "user-friendly" as using the yum or rpm command, this method is useful if the application is NOT contained in regular software repositories...

Use centos2
Perform these steps in the centos2 virtual machine.

In order to build software from source code, you must have the appropriate software development tools (such as make and gcc) and libraries (such as GTK) installed. The required tools will vary depending on the computer languages used in the software being built.

1. Issue the following command to install a basic set of development tools and libraries:
   yum groupinstall "Development Tools" "Development Libraries"

Installing Development Libraries
In the future, remember the above procedure whenever installing software from source. Sometimes, you need to install additional tools or libraries in order to compile a particular software package

3. Go to the directory /tmp
4. Use the wget command to download the "tar ball" that contains the source code for the NLED text editor. wget is a command-line tool to download files from the web using the http or ftp protocols.
   • wget http://cdot.senecac.on.ca/software/nled/nled_2_52_src.tgz
5. Extract the files. Change to the newly-extracted directory (/tmp/nled-2.52)
6. Check to see if there is a file named configure. If so, run it; if not, skip this step. (Most but not all source code archives contain this file)
7. Check to see if there is a file named Makefile or makefile. If so, type the command:
   • make
   • Did the command work? Why? Use the yum command to install the package gcc. What do you think the package gcc does?
8. Reissue the make command. Where you successful? What does make do?
9. In this case, you need to install the ncurses development libraries as well. Issue the following command as root: yum install ncurses-devel.x86_64. Now issue the command: make
10. Some software distributed as source code can automatically install itself. Try this command:
    • make install
11. Most but not all source code archives include the capability of installing themselves this way.
12. If the command make install does not work (how can you tell? What command did you learn from ULI101 to confirm that this command cannot be run from the command line?), copy the nled program manually:
    • cp nled /usr/local/bin
13. Test nled to make sure it works.
14. Why did copying the nled executable to /usr/local/bin allow the nled command to be run by name anywhere in the command prompt?

Answer the Investigation 3 observations / questions in your lab log book.

Managing Run-Levels and System Services

Investigation 4: How do we Manage Runlevels?

Use centos2 and centos3
Perform these steps in both of these virtual machines.

The runlevel command is now deprecated in Fedora, and will likely be deprecated in RHEL/CentOS at some point as well, but for now this is what the industry is using.

1. Issue the following Linux command:
   • runlevel
2. Note the difference in output between centos2 and centos3.
3. You can use the init command to change the current runlevel. See a list of runlevels here. Use the man command to learn how to use the init command. Use this command to change the current runlevel in centos2 to 3. What happened? What happens after your reboot?
4. Change the default runlevel on centos2 to 3. What happens now after you reboot?
5. Issue the following Linux command:
   • startx
6. What happens?
7. Log-off your graphical system. You should return to your shell prompt.
8. Change the default runlevel for centos2 back to 5 and reboot to make sure it works.

Answer the Investigation 4 observations / questions in your lab log book.

Investigation 5: How do we Manage System Services?

Remain in your centos2 VM
Perform these steps in the centos2 virtual machine.

We have seen that maintaining unneeded packages can be a security risk due to the unnecessary increase in the complexity of your system. Similarly, it is also unnecessarily hazardous, and even more so, to leave unneeded services running. In this investigation, we will learn how to control services, and turn off those services that we think are not necessary to help reduce security risks.}}

1. Issue the following Linux command:
   • service --status-all
2. Note the services that are currently running.
3. Use the service command to stop the service named iptables
4. Issue the service command to verify that this service has stopped.
5. If you reboot now - the iptables service will be turned back on. We don't want it on though, it causes students headaches. To turn it off permanently we need to use the chkconfig command: chkconfig iptables off
6. Reboot and confirm that it's no longer running.

Answer the Investigation 5 observations / questions in your lab log book.

Completing the Lab

Arrange evidence for each of these items on your screen, then ask your instructor to check each item:

1. Compressed files: /tmp/archive1.tar.gz and /tmp/archive2.tgz
2. nled application is installed
3. Lab5 notes how to use service/chkconfig commands
4. VMs backed-up

Preparing for Quizzes

1. What is the advantage of disabling services such as bluetooth?
2. What is the difference between a .tgz file and a .tar.gz file? What do these stand for?
3. What is the purpose of a repository?
4. What is source code?
5. How do you build software from source code?
6. Which is preferred: installing from an RPM file, or installing from source code? Why?
7. How do you use service/init/chkconfig to:
   • show/set current runlevel
   • list services
   • stop a service
   • start a service
   • Why is it important to learn how to manage services?
   • Why is it important to stop certain services?

Backup your work
Backup your disk images for centos2 and centos3 Virtual Machines.