=LAB PREPARATION=Purpose / Objectives of Lab 4=={| width="40%" align="right" cellpadding="10"|- valign="top"|[[Image:users.png|thumb|right|150px|System administrators are required to add, remove and modify user accounts.]]|[[Image:on-off.png|thumb|right|135px|In order to perform maintenance, system administrators need to know how to stop and start services for a Linux system. ]]|}

<u>Main objectivesObjectives</u>:

# Create a new user account called '''noobie''' for the employee: '''"Really Green"''' . Assign a password for that newly created user.

# Use the '''usermod''' command to change the full name of the user account '''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?

Many students may think that the following topic is small =INVESTIGATION 2: Managing System Services and "not a big deal". Those students may say, "How hard is running and stopping services?"Run-levels=

The process Many students may not be hard, but knowing how to stop, start, restart and check think that the status of services following topic is absolutely critical to small and "not a Linux serverbig deal". Aside from learning to trouble-shoot problems by checking the status of running servicesThose students may say, understanding how to manage services is critical to help protect a Linux server from penetration (this term is referred to as "'''Hardening a system'''"). Sometimes it How hard is "what we don't know" that can harm us. One key element in hardening a computer system is to disable non essential networkng services to allow IDSs ('''Intrusion Detection Systems''') to focus on a narrower range of policy violations. Learning to monitor the status, enable running and disable networking stopping services underlies the '''Backtrax''' motto:<br><br>'''"The quieter you are, then more you will hear...?"'''

===Part 1: How do we Manage RunlevelsSystem Services?===

#Perform this part We have seen that maintaining unneeded '''packages can be a security risk''' due to the unnecessary increase in both the complexity of your centos2 and centos3 VMssystem.The runlevel command Similarly, it is now deprecated in Fedoraalso unnecessarily hazardous, and even more so, to leave unneeded services running. In this investigation, we will likely be deprecated in RHEL/CentOS at some point as welllearn how to '''control services, but for now this is what the industry is usingand turn off those services that we think are not necessary to help reduce security risks'''.

<li value="2">Use the '''man''' pages to learn about the '''service''' command.</li><li>Issue the following Linux command:

<li><b><code><span style="color:#3366CC;font-size:1.2em;">runlevelservice --status-all</span></code></b></li>

<li>Note the difference in output between centos2 and centos3services that are currently running.</li> <li>You can use Use the command <b><code>init<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 change verify that the '''iptables''' service has stopped.<br><br>'''NOTE:''' Although the current runlevelservice command seems to work, it is <u>'''deprecated'''</u> (i. See a list of runlevels e. "out-dated:). It has been replaced by using the [httpshttp://wwwzenit.senecac.centoson.orgca/docswiki/5index.php/Init_vs_systemd#systemd_Command_Usage systemctl] command. This is a command based upon a newer method of starting and managing system services called [http:/html/5zenit.2senecac.on.ca/wiki/Installation_Guideindex.php/s2-Init_vs_systemd systemd] (which replaces init-boot-shutdown-rlthe "initialization table").html here]This method allows services to run more independently of each other, so that a service may be stopped without other dependent services to be stopped as well. Use the <codebr>man</codebr> command The most common '''systemctl''' commands are shown below (it is optional to learn how to use include the filename extension '''.service''' after the service-name):<codeul><li><span style="font-family:courier;font-size:1.2em;font-weight:bold;">'''systemctl list-units --all'''</codespan>init command&nbsp; (get a listing of all service names. Use this command Can pipe to grep to change the current runlevel list service you are interested in centos2 to 3. What happened? What happens after your reboot?)</li> <li>Change the default runlevel on centos2 to 3<span style="font-family:courier;font-size:1. What happens now after you reboot?2em;font-weight:bold;">'''systemctl status service-name'''</span> &nbsp; (Confirm status of a service - running or not-running)</li> <li>Issue the following Linux command<span style="font-family:courier;font-size:1.2em;font-weight: bold;">'''systemctl stop service-name'''</span> &nbsp; (stop a service)<ul/li> <li><bspan style="font-family:courier;font-size:1.2em;font-weight:bold;">'''systemctl start service-name'''</span> &nbsp; (start a service)</li><codeli><span style="colorfont-family:#3366CCcourier;font-size:1.2em;font-weight:bold;">startx'''systemctl restart service-name'''</span>&nbsp; (restart a service)</codeli><li><span style="font-family:courier;font-size:1.2em;font-weight:bold;">'''systemctl enable service-name'''</bspan>&nbsp; (enable service so service runs upon system startup)</li> <li><span style="font-family:courier;font-size:1.2em;font-weight:bold;">'''systemctl disable service-name'''</ulspan> &nbsp; (disable service so it does NOT run upon system startup)<br><br> </li> <li/ul>What happens?</li> <li>LogIf you reboot now -the iptables service will be turned back on. We don't want it on though, it causes students headaches.<br>To turn it off your graphical systempermanently we need to use the '''systemctl''' command:<b><code><span style="color:#3366CC;font-size:1. You should return 2em;">systemctl disable iptables</span></code></b><br>(the '''chkconfig''' command used to be the way to your shell promptenble/disable services, but is now deprecated).</li> <li>Change Use the default runlevel for centos2 back '''systemctl''' command to 5 verify that the '''iptables''' service is no longer running ('''hint:''' issue command, and reboot pipe to make sure grep "'''iptables'''"). <li>Reboot and confirm that it works's no longer running.</li>

=== Part 2: How do we Manage System ServicesRunlevels? === 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).

We have seen that maintaining unneeded '''packages The Linux sysadmin can be also change the run-level (or state) of a security risk''' due graphical Linux server to the unnecessary increase run in text-based mode and run the complexity of your systemgraphical mode by issuing a command when graphic mode is required. Similarly, it The run-level term is also unnecessarily hazardousnow deprecated in Fedora, and even more sowill likely be deprecated in RHEL/CentOS at some point as well, to leave unneeded services running. In but for now 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'''is what the industry is using.}}

  #For Perform this part, remain in both your '''centos2 VM''' and '''centos3''' VMs.

<li><b><code><span style="color:#3366CC;font-size:1.2em;">service --status-allrunlevel</span></code></b></li>

<li>Note the services that are currently runningdifference in output between '''centos2''' and '''centos3'''.</li> <li>Use You can use the '''init''' command to change the <b><code><span style="color:#3366CC;fontcurrent run-sizelevel. See a list of runlevels [https:1//www.centos.org/docs/5/html/5.2em;">service<2/Installation_Guide/span>s2-init-boot-shutdown-rl.html here].</codeli></bli> Use the '''man''' command to stop learn how to use the service named '''iptablesinit'''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;">servicestartx</span></code></b> command to verify that this service has stopped.</li> </ul> </li> <li>What happens?</li> <li>If you reboot now Log- the iptables service will be turned back onoff your graphical system. We don't want it on though, it causes students headachesYou should return to your shell prompt. To turn it off permanently we need to use the chkconfig command:<br/li> <bli><code><span style="colorUsing systemd requires a different method of setting text mode and graphical mode. You can refer to this link for future reference:#3366CC;font-size[http:1//fedoraproject.2em;">chkconfig iptables off<org/wiki/span>Systemd#How_do_I_change_the_runlevel.3F How to Change Run-Levels with Systemd]</codeli></bli>Restart your centos2 machine, and make certain that it runs in '''graphical''' mode</li> </li>Reboot and confirm that it's no longer running.Why would you want to make a graphical Linux system run in text-based mode?</li>

{{Admon/tip|Bash Shell Scripting Tips:|<br><ul><li>'''The case statement:'''<br><br>The case statement is a control-flow statement that works in a similar way as the if-elif-else statement (but is more concise). This statement presents scenerios or "cases" based on values or regular expressions (not ranges of values like if-elif-else statements). After action(s) are taken for a particular scenerio (or "case"), a break statement (''';;''') is used to "break-out" of the statement (and not perform other actions). A default case (*) is also used to catch exceptions.<br><br><u>'''Examples (try in shell script):'''</u><br><br>''read -p "pick a door (1 or 2): " pick<br>case $pick in<br>&nbsp; 1) echo "You win a car!" ;;<br>&nbsp; 2) echo "You win a bag of dirt!" ;;<br>&nbsp; *) echo "Not a valid entry"<br>&nbsp;&nbsp;&nbsp;&nbsp; exit 1 ;;<br>esac''<br><br>''read -p "enter a single digit: " digit<br>case $digit in<br>&nbsp; [0-9]) echo "Your single digit is: $digit" ;;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *)&nbsp;echo "not a valid single digit"<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; exit 1 ;;<br>esac''<br><br></li><li>'''The getopts function:'''<br><br></li></ul>The getopts function allows the shell scripter to create scripts that accept options (like options for Linux commands). This provides the Linux administrator with scripts that provide more flexibility and versatility. A built-in function called '''getopts''' (i.e. get command options) is used in conjunction with a '''while''' loop and a '''case''' statement to carry out actions based on if certain options are present when the shell script is run. The variable '''$OPTARG''' can be used if an option accepts text (denoted in the getopts function with an option letter followed by a colon. Case statement exceptions use the ''':)''' and '''\?)''' cases for error handling.<br><br>'''<u>Example of getopts</u>''' (try in script and run with options)<br><br>''while getopts abc: name<br>do<br>&nbsp; case $name in<br>&nbsp; &nbsp; a) echo "Action for option \"a\"" ;;<br>&nbsp; &nbsp; b) echo "Action for option \"b\"" ;;<br>&nbsp; &nbsp; c) echo "Action for option \"c\""<br>&nbsp; &nbsp; &nbsp; &nbsp; echo Value is: $OPTARG" ;;<br>&nbsp; &nbsp; :) echo "Error: You need text after -c option"<br>&nbsp; &nbsp; &nbsp; &nbsp; exit 1 ;;<br>&nbsp; &nbsp; \?) echo "Error: Incorrect option"<br>&nbsp; &nbsp; &nbsp; &nbsp; exit 1 ;;<br>esac''<br>done<br><br>}}

#Use the <b><code>wget</code></b> command to downloadYou will be using your '''c7host''' machine for this section.#Download, study, and run the following shell scripts on-linescript. Issue the command:<blockquotebr><b><code><span style=" pointer-events:none;cursor:default;color:#3366CC;font-size:1.2em;">wget https://scs.senecac.on.ca/~murray.saul/user-create.bash</span></code></b>

<ol><li value="3">Open a Bash shell terminal and login as root.</li><li>Use the wget command to download the input file called user-data.txt by issuing the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">wget https://scs.senecac.on.ca/~murray.saul/user-data.txt</span></code></b></li><li>View the contents on the user-data.txt file to confirm there are 3 fields (username, fullname, and e-mail address)which are separated by the colon (:) symbol.<li><li>Use a text editor (such as <b><code><span style="color:#3366CC;font-size:1.2em;">vi</span></code></b> or <b><code><span style="color:#3366CC;font-size:1.2em;">nano</span></code></b>) to create a Bash Shell script called: <b><code><span style="color:#3366CC;font-size:1.2em;">createUsers.bash</span></code></b> in /root's home directory.</li><li>Enter the following text content into your text-editing session:</li></ol>

&#35;<br>&#35; USAGE:<br>&#35;<br>&#35; /root/createUsers.bash [-i {input-path}] <br>

if [ $HOME PWD != "/root" ] # only runs if logged in as root's home directory<br>then<br>&nbsp;echo "You must be logged in as root's home directory." >&2<br>

while getopts i:n:a:g:o: name<br>

set $(sed 's/ /+/g' $inputfileinputFile) # temporarily convert spaces to + for storing lines as positional parameters<br>

&nbsp; &nbsp; userPassWd=$(date | md5sum | cut -d" " -f1)<br>&nbsp; &nbsp; useradd -m -c "$(echo $x | cut -d":" -f2 | sed 's/+/ /g')" -p $(date | md5sum | cut -d" " -f1) userPassWd $(echo $x | cut -d":" -f1)<br>

&nbsp; &nbsp; password: $(date | md5sum | cut -d" " -f1)userPassWd<br>

{{Admon/important|Time for a new backup!|If you have successfully completed this lab, make a new backup of your virtual machinesas well as your host machine. Remember to also make a backup of the new second virtual disk drive on ''centos1'' -- you now have two virtual disks on ''centos1'', and therefore two image files, and therefore will need two backup files.|}}

::<ol><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''centos1''' VM:<blockquote><ul><li> Account created on '''centos3centos1''' VM</li><li> List contents of '''/etc/group''' file (ops235 group)</li><li>List contents of '''/etc/passwd''' matching your Matrix account.::file (created accounts)</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> List contents of '''/etc/groupcentos2''' file (ops235 group).:VM:<blockquote><ul><li>Display current run-level status on '''centos2''' VM</li></ul></blockquote></li></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> List contents '''c7host''' machine<blockquote><ul><li>Creation of your bash shell script called '''/etc/passwdcreateUsers.bash''' file (created accounts).::</li></ul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> Creation of your bash shell script called '''createUsers.bashLab4'''log-book filled out.</li></ol> 

= Preparing for the = Practice For Quizzes , Tests, Midterm &amp; Final Exam ==