OPS235 Lab 5 - Fedora17

OPS235 Lab 5 - Loopback Filesystems, Archives, Compiling from Source

Caution!
This lab is under construction.

Objectives

1. To create and use loopback filesystems in read-write mode
2. To create and use archive files (tar and tar.gz)
3. Compiling software from source code
4. Customizing system startup

References

• man pages for mount, fstab, tar, gzip, make, chkconfig, dd, service
• Resources on the web:
  • Services in Fedora 12
  • How to use the dd command

Required Material

• SATA Hard Disk with Fedora 12 (the same one used for Lab 3 and 4)
• Lab log book

Prerequisites

• Completion of Labs 1-4

Introduction

There are two techniques used to place multiple files within one file: the first is to create a filesystem within a file, and the second is to use an archive program to create an archive file. 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. Finally, you will modify your system startup to eliminate unnecessary services and configure your system to automatically mount a partition.

Investigation 1: How do you create and use a filesystem in a regular file?

Use fedora3
Perform these steps in the fedora3 virtual machine.

1. Login using your Learn ID
2. Create an empty file that is exactly 3 MB in size:
   • dd if=/dev/zero of=/tmp/fstest bs=1k count=3072
3. How does this command ensure that the file is 3 MB in size? What is in the file at first?
4. Create an ext3 filesystem within the newly-created file /tmp/fstest. Note the warning message/question that appears
5. Mount the filesystem (remember to use the loopback option; refer to Lab 1 if required). Use a mountpoint of your choosing.
6. Copy the files /etc/services and /etc/protocols to the filesystem mounted in the previous step
7. Unmount the filesystem
8. Test your filesystem to be sure that the files /etc/services and /etc/protocols were in fact copied into the filesystem within the file named /tmp/fstest.
9. How much space is left in that filesystem? (Hint: df -h).

Make sure that your lab notes answer the Investigation 1 question.

Investigation 2: How do you create an archive file?

Use fedora3
Perform these steps in the fedora3 virtual machine.

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.

1. Change your working directory to /usr/share/doc/sudo*
2. Use the tar (tape archiver) command to create an archive file named /tmp/archive1.tar
   • tar cvf /tmp/archive1.tar .
3. What do the options c, v, and f mean?
4. Record the archive file size.
5. Compress the file using gzip:
   • gzip /tmp/archive1.tar
6. Record the archive file size after compression.
7. Make sure you're still in /usr/share/doc/sudo* and then create a compressed archive:
   • tar cvzf /tmp/archive2.tgz .
8. What does the z option do?
9. Compare the sizes of /tmp/archive1.tar.gz and /tmp/archive2.tgz. Why are they so close in size?

Answer the Investigation 2 question.

Investigation 3: How do you restore files from an archive?

Use fedora3
Perform these steps in the fedora3 virtual machine.

1. Create the directory /tmp/extract1 and make it your current working directory (change into that directory).
2. Unzip the first archive you created:
   • gunzip /tmp/archive1.tar.gz
3. Extract the files from the first archive:
   • tar xvf /tmp/archive1.tar
4. Are all the files there?
5. Compare /tmp/extract1/README and /usr/share/doc/sudo*/README. Are they exactly the same? Why?
6. Create the directory /tmp/extract2 and make it your current working directory.
7. Extract the files from the second archive:
   • tar xvzf /tmp/archive2.tgz
8. Note that this time a separate gunzip command was not needed. Why?
9. Compare the README file in this directory with the original file. Are they exactly the same?

Answer the Investigation 3 question.

Investigation 4: How do you build software from source code?

Use fedora2
Perform these steps in the fedora2 virtual machine.

Compiling requires the correct tools to be installed.
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.

Software Development Tools Required
You may need to install gcc (GNU C Compiler) and ncurses-devel (Development Library) in order to complete this investigation successfully. Use yum to install these packages if you get an error message saying the cc command was not found or the ncurses library is not found.

1. Go to the directory /tmp
2. Use the wget command to download the "tar ball" that contains the source code for the NLED text editor.
   • wget http://cdot.senecac.on.ca/software/nled/nled_2_52_src.tgz
3. Extract the files. Change to the newly-extracted directory (/tmp/nled-2.52)
4. 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)
5. Check to see if there is a file named Makefile or makefile. If so, type the command:
   • make
6. What does make do?
7. Some software distributed as source code can automatically install itself. Try this command:
   • make install
8. Most but not all source code archives include the capability of installing themselves this way.
9. If the command make install does not work (how can you tell?), copy the nled program manually:
   • cp nled /usr/local/bin
10. Test nled to make sure it works.

Answer the Investigation 4 question.

Investigation 5: How do we turn system services on and off?

Use fedora2
Perform these steps in the fedora2 virtual machine.

Security Advice
We have seen that maintaining unneeded users and groups 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 that we think are not necessary.

1. Determine your current runlevel using the runlevel command.
2. Change to the appropriate startup directory in a terminal window. For example, if your runlevel is 4, change to /etc/rc.d/rc4.d
3. Observe the names of the symbolic links in that directory.
4. Where do the links link to?
5. Run the menu option System>Administration>Services. You will then see the Service Configuration screen.
6. Find the isdn service and select customize from the tool bar. and deselect the checkbox for your runlevel from step 1. Quit the app.
7. Return to the terminal window you used in Step 2. Get a listing of the symbolic links in the startup directory. Is it any different from what you observed previously?
8. Using the Service Configuration screen, re-enable the isdn service.
9. Check the symbolic links again. What has changed this time?
10. Run this command:
    • chkconfig isdn off
11. Now what has changed in the directory?
12. Run this command:
    • chkconfig isdn on
13. Now what has changed?
14. Run the command:
    • chkconfig --list

     What does the output show?
 14. What is the relationship between the Service Configuration tool, the symbolic links in the startup directory, and the chkconfig command?
 15. You can also set services to be on or off for certain runlevels. For example, to turn httpd on for runlevel 4, we issue the command:

          chkconfig  --level 4 httpd on

     To turn it off, we type:

          chkconfig  --level 4 httpd off

 16. To increase your computer's security, make sure these services are disabled:

     anacron, bluetooth, cups, irda, irqbalance, isdn, mdmonitor, netfs, nfs, nfslock, pcscd, rpcgssd, rpcidmapd, rpcsvcgssd, sendmail, ypbind.

     You should understand that while most services in this list are often not needed, or are needed under circumstances different than those which occur here, there may be situations in which some of them are required, and it may be up to you as an administrator to determine which services are needed, and which should be turned off.

 17. Finally, make sure the gpm service runs in runlevel 3, but not in 5.

Answer the Investigation 5 question.