We will now learn how to perform these operations (including monitoring of disk space usage) in Part 1.
== Part 1: The /etc/passwd file Mounting and Un-mounting Partitions ==
# Look at the <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/passwd</span></code></b> file.# Make note of the contents of that file.# Read about the file: http://man7.org/linux/man-pages/man5/passwd.5.html # Make sure you know what information each field contains.# Why do you think there are so many users?# Look at the names of the users. What do you think these user names represent? Are they people?# What is the numeric user ID (UID) of the root user?# The user IDs of real users (people) are different from the user IDs of system accounts. What is the pattern?x
'''Answer the Part 1 observations / questions in your lab log book.'''
== Part 2: Adding users Obtaining File System Information ==
# x
#Perform this part in your '''centos1''' VM.# Read Answer the man page for the <b><code><span style="color:#3366CC;font-size:1.2em;">useradd</span><Part 2 observations /code></b> command.# Create three fictitious users (make-up their userids and full names. Give each of these newly-created users a password.# Grep the <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/passwd</span></code></b> file for each of the new users.#* What is the '''home''' directory of each user?#* What '''group''' is each user in?#* What other information can you provide regarding these users?#* Where are the '''passwords''' stored?# Look at the man page for '''/etc/shadow''' using the command: <b><code><span style="color:#3366CC;font-size:1.2em;">man 5 shadow</span></code></b>#* Grep the <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/shadow</span></code></b> file for each of the new users.#* Make note of this information. # Create two new dummy users, <b><code><span style="color:#3366CC;font-size:1.2em;">ops235_1</span></code></b> and <b><code><span style="color:#3366CC;font-size:1.2em;">ops235_2</span></code></b>.# Investigate the home directory of one of your new users.#* What files are there? Be sure to include hidden files.#* What do you think these files are used for?#* How does the operating system determine which files are created in a new home account? The answer can be found here:<br>http://www.linuxhowtos.org/Tips%20and%20Tricks/using_skel.htm#* Look at the files (including hidden files) in the template directory referred to in the article. Compare them to what is in a home directory for a new user. What do you notice?#* Create a new file in this directory with the following command: <b><code><span style="color:#3366CC;font-size:1.2em;">touch foo</span></code></b>#* Create a new user named <b><code><span style="color:#3366CC;font-size:1.2em;">foobar</span></code></b>, with the option to automatically create a home directory.#* Look at the contents of foobar's home directory. What do you notice?# Be sure to record your observations questions in your lab notes.#Issue the man pages for the '''useradd''' commandlog book. Explain the purpose of using the '''-e''' option for the ''useradd'' command. Try to think what would be the purpose for a Linux sysadmin to use this option when creating new users.
'''Answer the Part 2 observations / questions in your lab log book.'''
== Part 3: Managing Groups ==
#Remain in your '''centos1''' VM for this section.# Read the man page for the <b><code><span style="colorINVESTIGATION 2:#3366CC;font-size:1.2em;">groupadd</span></code></b> and <b><code><span style="color:#3366CC;font-size:1.2em;">groupdel</span></code></b> commands.# Note which option allows you to set the Group ID number ('''GID''') when you create a new group.# Examine the file <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/group</span></code></b>#* Which values of GID are reserved for system accounts?#* Which values of GID are reserved for non-system user accounts?#* What is the lowest available GID number for non-system users?#* What is the default group name of a new user?#* Add a new group named <b><code><span style="color:#3366CC;font-size:1.2em;">ops235</span></code></b> Adjusting File System Sizes with a GID of <b><code><span styleLVM="color:#3366CC;font-size:1.2em;">600</span></code></b>.#* The management at your organization have concerns regarding some irresponsible users on your system.#** Add a new group named '''investigation'''.#** Look at '''/etc/group''' and note the GID of group called '''investigation'''.#** What GID is given to a new group if you do not specify it?#** In the file, add those users to the end of the concerned group (separate each user-name with a comma).#** Those individuals have explained their actions to management and the crisis has been resolved. Delete the '''investigation''' group.#** Look at '''/etc/group''' again and note the change.
'''Answer the Part 3 observations / questions in your lab log bookMonitoring and ensuring adequate space for a Linux file-system is considered to be an important task for a sys admin.'''
=== Part 41: Deleting / Modifying Users Obtaining System Information with LVM ===
#Remain in your '''centos1''' VM for this section.# Read the man page for the '''userdel''' command. Note which option automatically removes the users home directory when We have seen that user is deleted.# Delete the user maintaining unneeded '''ops235_1packages can be a security risk''' using due to the command <b><code><span style="color:#3366CC;font-size:1.2em;">userdel ops235_1</span></code></b># Delete the user '''ops235'''_2 using unnecessary increase in the same command with the option which removes the home directory complexity of the user.# Check the contents of the /home directory. What do you notice?# Check the contents of the <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/group</span></code></b> file. What do you notice?# Read the man page for the usermod commandyour system. Note which options change the user's full nameSimilarly, primary groupit is also unnecessarily hazardous, supplementary groupsand even more so, and shell.# Create a new user account called '''noobie''' for the employee: '''"Really Green"''' . Assign a password for that newly created userto leave unneeded services running.# Management has indicated that In this employee be on on probation for 3 months. Use the '''usermod''' command to set the account for noobie to expire in 3 months from this day as part of the security policy of this organization.# Add each of your new users to the group ops235 (in other wordsinvestigation, add ops235 we will learn how to each user as a supplementary group).# Examine <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/group</span></code></b>. What has changed?# Use the '''usermod''' command control services, and turn off those services that we think are not necessary to change the full name of the user account help reduce security risks'''noobie''' from '''"Really Green"''' to '''"Outstanding Employee"'''. Examine the result of running that command in the <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/passwd</span></code></b> file. What has changed?# Use the '''usermod''' command to extend the use of their account for 5 years as of today.# Be sure to record your observations in your lab notes.}}
'''Answer the Part 4 observations / questions in your lab log book.'''# x
=INVESTIGATION 2: Adjusting File System Sizes with LVM='''Answer Part 1 observations / questions in your lab log book.'''
Monitoring and ensuring adequate space for a Linux file-system is considered to be an important task for a sys admin.
=== Part 12: How do we Manage System Services? Adjusting Partition Sizes with LVM===
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'''.}}x
#Use your '''centos2''' VM for this part.
<ol>
<li value="2">Use the '''man''' pages to learn about the '''service''' command.</li><li>Issue the following Linux command:
<ul>
<li><b><code><span style="color:#3366CC;font-size:1.2em;">service --status-all</span></code></b></li>
</ul>
</li>
<li>Note the services that are currently running.</li>
<li>Use the command <b><code><span style="color:#3366CC;font-size:1.2em;">service iptables stop</span></code></b> to stop the service named '''iptables'''</li>
<li>Run a command to verify that the '''iptables''' service has stopped.</li>
<li>A newer method of managing services is by using '''systemd'''. It has the ability to manage dependent service in parallel and allow one service to be stopped without disrupting the other services. Here is a link that briefly explains how to use '''systemd''' (as opposed to tradition method: ''init'') and the '''systemctl''' command: [http://zenit.senecac.on.ca/wiki/index.php/Init_vs_systemd init vs systemd]</li>
<li>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:<br><b><code><span style="color:#3366CC;font-size:1.2em;">chkconfig iptables off</span></code></b></li>
<li>Use the '''systemctl''' command (from the link above - showing examples) to verify that the '''iptables''' service is off ('''hint:''' issue command, and pipe to grep "'''iptables'''").
<li>Reboot and confirm that it's no longer running.</li>
</ol>
'''Answer Part 1 observations / questions in your lab log book.'''# x
==='''Answer Part 2: How do we Manage Runlevels?===observations / questions in your lab log book.'''
Running servers in graphical mode will make your system most likely to be penetrated. The X-windows framework can be vulnerable to attacks when these servers are connected to the Internet. This is why when you install server versions of Linux, they work in text-based mode only. Desktop versions of Linux are then installed on workstations (working in graphical mode) that connect to the server (for security reasons).===Part 3: Adding Virtual Hard Disks and Managing with LVM===
The Linux sysadmin can also change the run-level (or state) of a graphical Linux server to run in text-based mode and run the graphical mode by issuing a command when graphic mode is required. The run-level term 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.x
# x
#Perform this part in both your '''centos2''' and '''centos3''' VMs.
<ol>
<li value="2">Issue the following Linux command:
<ul>
<li><b><code><span style="color:#3366CC;font-size:1.2em;">runlevel</span></code></b></li>
</ul>
</li>
<li>Note the difference in output between '''centos2''' and '''centos3'''.</li>
<li>You can use the '''init''' command to change the current run-level. See a list of runlevels [https://www.centos.org/docs/5/html/5.2/Installation_Guide/s2-init-boot-shutdown-rl.html here].</li><li> Use the '''man''' command to learn how to use the '''init''' command. Use this command to change the current run-level in '''centos2''' to '''3'''. What happened?</li>
<li>Issue the following Linux command:
<ul>
<li><b><code><span style="color:#3366CC;font-size:1.2em;">startx</span></code></b></li>
</ul>
</li>
<li>What happens?</li>
<li>Log-off your graphical system. You should return to your shell prompt.</li>
<li>Using systemd requires a different method of setting text mode and graphical mode. You can refer to this link for future reference:
[http://fedoraproject.org/wiki/Systemd#How_do_I_change_the_runlevel.3F How to Change Run-Levels with Systemd]</li><li>Restart your centos2 machine, and make certain that it runs in '''graphical''' mode</li>
</li>Why would you want to make a graphical Linux system run in text-based mode?</li>
</ol>
'''Answer Part 3 observations / questions in your lab log book.'''
'''Answer Part 2 observations / questions in your lab log book.'''
= INVESTIGATION 3: LOOKING AHEAD =
==Automating Routine Tasks (Shell Scriptingand Using Crontab)==
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