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OPS245 Lab 2

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→‎Practice For Quizzes, Tests, Midterm & Final Exam

{{Admon/important|Run virt-manager as a regular user, not as root|Otherwise all your virtual machines will be owned by root and you won't be able to use them as a regular user.}}

<ol>

<li value="8">Start the graphical tool by selecting the menu options '''Applications'''>'''System Tools'''>'''Virtual Machine Manager''' or by typing the command<code> virt-manager</code>(without sudo!)</li>

<li>You will be learning in the next investigation to perform several different types of CentOS Linux installs.</li>

</ol>

===Part 2: Configure VMware Workstation for Nested VMs ===

:: '''Boot media:''' Network installation

:: '''CentOS Full Network Install URL:'''

:::*Seneca Lab: https://mirror.senecacollege.ca/centos/7/os/x86_64/('''NOTE: requires VPN''')

:::*Home: https://mirror.netflash.net/centos/7/os/x86_64/

:: '''VM Image Pathname:''' /var/lib/libvirt/images/centos1.qcow2

# Another dialog will appear. Click '''CPUs''' (or "processors") and on right-side under Configuration select '''Copy Host CPU Configuration''', click '''Apply''', and then click '''Begin Installation''' at the top left-hand side.

#During the install, select '''Gnome Desktop''' software selection). For partitioning, select '''I will configure partition settings''', click done, then select '''Click here to create them automatically'''. Set the / partition for '''ext4''' file-system type, and click '''Done'''.

#Set the correct '''Date and Time Zone''', and then click on '''Network and Hostname'''. The network should be turned on'''ON'''. For hostname, enter: '''centos1''' and then click '''Done'''.

# Make sure that when you create your regular user account you check the box to make them an administrator.

# Complete the installation. Login to your regular user account, and perform a '''sudo yum update''' for the centos1 VM (reboot if required). Make certain to adjust your screen-saver settings if desired.

{{Admon/important|Use same root password / regular username / regular user passwords for c7host and ALL VMs|To simplify the lab checking process make certain that you use the identical root password, regular username, and regular username password for VMs that you create in this labs as you did for c7host machine in lab1. }}

<ol><li value="1314">Repeat the steps as you did in the previous investigation ([https://wiki.cdot.senecacollege.ca/wiki/~~OPS235_Lab_2~~OPS245_Lab_2#Part_1:_Install_KVM_Virtualization_Application Investigation1 Part 1]) to '''stop and disable firewalld, install iptables-services, start and enable iptables''' for this newly-created VM.</li>

<li>Repeat the steps as you did with c7host post-install to '''turn off SELinux''' and perform a '''yum update'''.</li>

<li>Issue the following command to obtain the IPADDR for your centos1 VM to record in your lab2 logbook: <code>ip address show</code></li>

:: '''Boot media:''' Network installation

:: '''CentOS Full Network Install URL:'''

:::*Seneca Lab: https://mirror.senecacollege.ca/centos/7/os/x86_64/('''NOTE: requires VPN''')

:::*Home: https://mirror.netflash.net/centos/7/os/x86_64/

:: '''VM Image Pathname:''' /var/lib/libvirt/images/centos2.qcow2

# Make certain to enter the name: '''centos2''', AND then select the option: '''Customize configuration before install''', and select '''Copy Host CPU Configuration''', click '''Apply''', and then click '''Begin Installation'''.

#When selecting the install options for centos2, do the same operation that you did in centos1 (but with '''Minimal Install''' software selection instead), but after '''automatically creating the partitions''', reduce the size of the root logical volume to '''8 GiB''' and add a logical volume with a size of '''2 GiB''' (mount point: '''/home''', name: '''home''', and make certain root and /home logical volumes have '''ext4''' file system).

# Complete the installation. Login to your regular user account.

#Repeat the steps as you did in the previous investigation ([https://wiki.cdot.senecacollege.ca/wiki/OPS235_Lab_2#Part_1:_Install_KVM_Virtualization_Application Investigation1 Part 1]) to '''stop and disable firewalld, install iptables-services, start and enable iptables''' for this newly-created VM.# Repeat the steps as you did with c7host post-install to '''turn off (permissive) SELinux''' (using the command 'vi' instead of 'vim') and perform a '''yum update'''.# Issue the following command to obtain and record your ~~centos3~~ centos2 IPADDR in your lab2 logbook: <code>ip address show</code>

# Record the time taken to install, and compare this to the time taken by the previous installations in your lab2 logbook.

:::*Home: http://mirror.netflash.net/centos/7/os/x86_64/

:: '''Kickstart File URL (Kernel options): '''

:::* Home:''' ks=https://ict.senecacollege.ca/~~~peter.callaghan/~~ops245/labs/centos7-kickstart.cfg

:: '''VM Image Pathname:''' /var/lib/libvirt/images/centos3.qcow2

:: '''Memory:''' 2048MB ('''IMPORTANT''' Do not use less than 2048MB during installation.)

# Create the VM (called '''centos3''')

# During the install, copy the network URL, then click the '''URL options''' to expand the '''kernel options''' input textbox. Type the following in the kernel options textbox: <ul><li>ks=https://ict.senecacollege.ca/~~~peter.callaghan/~~ops245/labs/centos7-kickstart.cfg</li></ul>

# Then click the '''forward''' button to proceed. Make certain to select the correct Memory Size and Disk Space size shown in the VM Details above

# Make certain to enter the name: '''centos3''', AND then select the option: '''Customize configuration before install''', and select '''Copy Host CPU Configuration''', click '''Apply''', and then click '''Begin Installation'''.

# Use the command <code>sudo -i</code> and enter your password if prompted. You are now root until you use the command <code>exit</code> to return to your normal user account.

# Change to the images directory by issuing the following command: <code> cd /var/lib/libvirt/images/</code>. Note that you did not need to use sudo, as you are already using elevated permissions.

# Make a compressed backup of your '''centos1.qcow2''', '''centos2.qcow2''', and '''centos3.qcow2''' files to your regular user's home directory by issuing each command (- one at a time(create '''backups''' directory before running these commands): <code>gzip < centos1.qcow2 > ~YourRegularUsername/backups/centos1.qcow2.gz</code> <code>gzip < centos2.qcow2 > ~YourRegularUsername/backups/centos2.qcow2.gz</code> <code>gzip < centos3.qcow2 > ~YourRegularUsername/backups/centos3.qcow2.gz</code><ul>'''NOTE:''' Make certain to use the redirection signs "<" and ">" properly in the command!</ul>

{{Admon/important |Please be patient|It may look like the command prompt is stuck but it could take a while for gzip to compress an entire operating system. '''NOTE:''' Do NOT press '''<ctrl>c''' to cancel this process. If you do, your archive will become incomplete and your recovery will be corrupt.}}

<ol><li value="57"> Compare the size of the compressed and original files (hint: use '''ls -lh'''). If file is very large (like 15GB), you didn't compress it and you need to remove that file and perform the previous step until you get it right!</li>

<li>Once you are sure you have all three VMs backed up, use the <code>exit</code> command to revert back to your normal user.</li>

<li> Start the '''''centos3''''' VM.</li>

<li> When the machine restarts it will not boot since all system files have been removed!</li>

<li> Use the '''Force Off''' option to turn centos3 back off.</li>

<li> Restore the original image from the backup from your home directory to your '''images''' directory by typing <code>sudo -i</code> command first [do not forget to '''exit''' when you are done], then this command: <code>~~sudo~~ gunzip < ~~~YourUserId~~YourRegularUsername/backups/centos3.qcow2.gz > /var/lib/libvirt/images/centos3.qcow2'''</code></li>

<li> Restart the VM. Is it working normally?</li>

<li> You should also make a copy of the XML configuration file for each VM in case you "wipe" and re-install the host machine, and want to add a restored VM backups to the virtual machine manager list. We will demonstrate using the centos3 XML configuration file, and prove that a "clone" can be added to your list.Please perform the following step:</li>

<li> Execute the following command: <code>sudo virsh dumpxml centos3 > centos3.xml</code></li>

<li> Examine the file <code>centos3.xml</code>. What does it contain? What format is it in? </li></ol>

# We will now learn how to download a compressed image file and XML configuration file and add it as a VM to the Virtual Machine Manager menu.

# Issue the following commands:<ul><li><code>wget https://ict.senecacollege.ca/~~~ops235~~ops245/centos4.qcow2.backup.gz</code></li><li><code>wget https://ict.senecacollege.ca/~~~ops235~~ops245/labs/centos4.xml</code></li></ul>

# Use gunzip with elevated privileges to decompress the qcow2 image file into the '''/var/lib/libvirt/images''' directory.

# Issue the command: <code>sudo virsh define centos4.xml</code># What happened in the virtual manager window? To In order to remove a VM entry in the Virtual Manager window, simply issue the command: '''virsh undefine ~~vm_name~~VM_name''' (without the '''.xml''' file extension)

# Start up your new centos4 VM.

# Click on the user OPS235, and click the cog icon.

::* In order to fully back up a virtual machine, what information should be saved in addition to the virtual machine image?

=== Part 3: Using ~~Shell Scripts~~ the Command Line for VM ~~Backup &~~ State Management===

{|width="40%" align="right" cellpadding="10"

|- valign="top"

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{{Admon/tip|Bash Shell ~~Scripting~~ Tips:| '''Data Input''' <ul><li>A shell ~~script~~ can obtain data from a number of methods: '''reading input files''', using '''arguments when issuing command''' (positional parameters), or '''prompting for data to store in a variable'''. The later method can be accomplished by using the '''read''' command. </li><li>Example: ''read -p "Enter your name: " userName''. </li></ul>'''Mathematical Expressions''' <ul><li>In the bash shell ~~scripting~~, data is stored in variable as text, not other data types (ints, floats, chars, etc) like in compiled programs like C or Java. In order to have a shell ~~script~~ perform '''mathematical operations''', number or variable need to be surrounded by two sets of parenthesis '''((..))''' in order to convert a number stored as text to a binary number. </li><li>Examples ''var1=5;var2=10'' ''echo "$var1 + $var2 = $((var1+var2))"'' '''Note:''' shell does not perform floating point calculations (like '''5/10'''). Instead, other commands like '''awk''' or '''bc''' would be required for floating point calculations (decimals) </li></ul>'''Loops (for / while / until)'''<ul><li>Determinant loops (such as '''for''' loops) usually repeat for a preset number of times (eg. counts, positional parameters stored). In-determinant loops (such as '''while''' or '''until''' loops) may repeat based on unknown conditions (like waiting for user to enter correct data). </li><li>Conditional statements '''&&''' (run if previous command or test is true) and '''||''' (run is previous command or test is false) can also be used when testing multiple conditions. </li><li>Examples: ''set ops235 is fun'' ''for x'' ''do''  ''echo "argument is $x"'' ''done'' ''for x in $(ls)'' ''do''  ''echo "Filename: $x"'' ''done'' ''read -p "enter a whole number: " num'' ''until echo $num | grep -q "^[0-9][0-9]*$"'' ''do''  ''read -p "Incorrect. Please enter WHOLE NUMBER: " num'' ''done'' ''read -p "pick a number between 1 and 10: " num'' ''while [ $num -lt 1 ] || [ $num -gt 10 ] ''do''  ''read -p "Incorrect. Please pick number between 1 and 10: " num'' ''done'' </li></ul>}}

|}

You will continue our use of the Bash Shell ~~scripting~~ by ~~first creating a Bash Shell script that~~ examining commands will allow the Linux sysadmin to ~~select~~ gather information about and manage their ~~created VMs for backup to root's home directory. Afterwards you will download, view and run a couple Bash Shell scripts that use the virsh command to start and stop your virtual machines~~Virtual Machines.

:'''Perform the following steps:'''

# Switch to the '''c7host''' machine, and open a shell terminal.

# Enter these admin commands into your '''c7host''' machine and note the result:

:: <code>sudo virsh list</code>:: <code>sudo virsh list --all</code>:: <code>sudo virsh list --inactive</code><ol><li value="4">Now, shut-down your centos1 VM normally, and close the centos1 VM window.</li><li>Switch to your terminal and issue the command: <code>sudo virsh start centos1</code></li><li>Using the appropriate command check to see if your centos1 VM is now running.</li><li>There are other commands that can be used (such as '''suspend''', or '''shutdown'''). The "shutdown" command may not always work since it relies on the guest handling a particular ACPI event. Why do you think it is useful to have commands to manipulate VMs?</li></ol>

{{Admon/important|Virtual Machine Does not Shutdown from Command|If the Virtual machine fails to shutdown from the <code>virsh shutdown</code> command, then you can go to the '''Virtual Machine manager''' and '''halt''' or '''shutdown''' within the VM itself, then you can click the '''PowerOff''' button in the VM window. You'll want to avoid a forced shutdown since those are equivalent to yanking the power cord out of the wall on a physical machine!|}}

~~<ol><li value="9">Open a Bash shell terminal.</li><li>Use elevated privileges to create a directory called /root/bin.</li>~~<li>Use a text editor (such as <code>vi</code> or <code>nano</code>) to create a Bash Shell script called: <code>backupVM.bash</code> in /root/bin directory.</li>~~<li>Enter the following text content into your text-editing session:</li></ol><code style="color:#3366CC;font-family:courier;font-size:.9em;">~~ ~~#!/bin~~/~~bash~~ ~~# backupVM.bash # Purpose: Backs up pre-defined virtual machines<br~~>~~#~~ ~~# USAGE: .~~/~~backupVM.bash #<br~~># Author: *** INSERT YOUR NAME *** # Date: *** CURRENT DATE *** ~~if [ $PWD != "~~/~~root" ] # only runs if in root's directory<br~~>~~then~~<br~~> echo "You must be located in~~ /~~root" >&2<br~~>~~ exit 1~~ fi</~~code~~> ~~<ol><li value="12">Save your editing session, but remain in the text editor.<~~/li><li>This shell script is designed particularly for your centos1, centos2, and centos3 VMS.</li><li>The code displayed below will prompt the user if they wish for all VMs to be backed-up; otherwise, allow the user the option of specifying which VMs to be backed-up. Add the following code</li></ol> ~~<code style="color:#3366CC;font-family:courier;font-size:.9em;">~~ ~~read -p "Backup all VMs? (y|n):" answer # prompt if all VMs to be backed-up~~ ~~if [ "$answer" = "y" ] # Backup all VMs if answer is yes then  for num in 1 2 3 # Determinant loop for 3 arguments: 1, 2, and 3  do   echo "Backing up VM #$num"   gzip < /var/lib/libvirt/images/centos$num.qcow2 > ~yourusername~~/~~backups/centos$num.qcow2.gz<br~~>~~   echo "VM #$num BACKUP DONE"  done elif [ "$answer" = "n" ] then  read -p "Which VM should be backed up? (1/2/3): " numanswer  until echo $numanswer | grep "^[123]$" >> /dev/null # Look for match of single digit: 1,2, or 3  do   read -p "Invalid Selection. Select 1, 2, or 3: " numanswer  done  echo "Backing up VM #$numanswer"  gzip < /var/lib/libvirt/images/centos$numanswer.qcow2 > ~yourusername/centos$numanswer.qcow2.gz  echo "VM #$numanswer BACKUP DONE" else  echo "Invalid Selection... Aborting program"  exit 2 ~~fi ~~</code>~~ ~~<ol>~~<li value="15">Save, set permissions, and then run that shell script to backup centos1. Since that script will only work if you are in root's home directory, you will need to use the technique you learned earlier to temporarily become root. Confirm that this script did backup this image to root's home directory</li><li>Use the <code>wget</code> command to download, study, and run the following shell scripts on-line:<blockquote><code>https://ict.senecacollege.ca/~ops235/labs/vm-start-text.bash https://ict.senecacollege.ca/~ops235/labs/vm-stop-text.bash</code> <code>https://ict.senecacollege.ca/~ops235/labs/vm-start.bash https://ict.senecacollege.ca/~ops235/labs/vm-stop.bash</code></blockquote></li><li>Try to understand what these Bash Shell scripts do.</li></ol>

'''Answer INVESTIGATION 3 observations / questions in your lab log book.'''

for machine in {'centos1','centos2','centos3'}:

print('Backing up' + machine)

os.system('gzip < /var/lib/libvirt/images/' + machine + '.qcow2 > ~YourRegularUsername/backups/' + machine + '.qcow2.gz')

</code>

<li>Modify the if statement so it is just getting the current username, not the username and a newline. You can do this using several steps and several variables, but it can also be done in a single line.</li>

<li>Now that the script recognizes you as being root (or at least running the script with root permissions), it should work. Notice how we've used the + to combine several strings together to pass to the os.system command. We did this because this script needs the python variable to be evaluated before the whole line gets handed over to os.system. If you left the variable names inside the quotes, python will ignore them as just being part of a string. By putting them outside of a string, and concatenating their value to that string, we can evaluate them and feed them into that command.</li>

<li>~~Convert the rest~~ Test your script to make sure it works. If it doesn't, go back and fix it. Do not continue until it successfully makes backups of your VMs.</li><li>There is a weakness to this script as written. Every time you run it, it will make a backup of all three VMs. But what if you only made a change to one of them? Do we really need to wait through a full backup cycle for two machines that didn't change? As the ~~bash~~ script ~~above into python~~is currently written, ~~then test~~ we do. But we can make it better.</li><li>Before the for loop that backs up each machine add a prompt to ask the user if they want to back up all machines. Use an if statement to check if they said yes.<ul><li>if they did say yes, back up all the VMs using your ~~python version~~ existing for loop.</li><li>If they didn't say yes, do nothing for now.</li></ul></li><li>Test your script to make sure it works. Check what happens if you say 'yes' to the prompt, and check what happens if you say things other than 'yes'.</li><li>Now we have a script that asks the user if they want to back up all VMS, and if they say they do it does. But if they don't want to back up every VM, it currently does nothing.</li><li>Add an else statement to handle the user not wanting to back up every VM. Inside that else clause ask the user which VM they would like to back up (you can even give them the names of available VMs (Centos1, Centos2, Centos3).</li><li>Now nest and if statement inside that else so that your script can handle what your user just responded with. If they asked for Centos1, back up Centos1. If they want to back up Centos2, only back up Centos2, etc. Hint: You might want to use elif for this.</li><li>Test your script again. You should now have a script that:<ul><li>Makes sure the user is running the script with elevated permissions.</li><li>Asks the user if they want to back up every VM.</li><li>If they want to back up every VM, it backs up every VM.</li><li>If they user does not want to back up every VM, the script asks them which VM they do want to back up.</li><li>If they user selected a single VM, the script will back up that one VM.</li></ul></li>

</ol>

# Inside each virtual machine, run <code>ip a</code> on the command line. Open a Terminal window in centos1 to do so. You'll need the IP address of each machine for the next steps.

# Switch to your '''c7host''' VM, open a terminal, login as root, and change directory to '''/root/bin'''.

# Issue the Linux command: <code>wget https://ict.senecacollege.ca/~~~peter.callaghan/~~ops245/labs/lab2-check.bash</code>

# Give the '''lab2-check.bash''' file execute permissions (for the file owner).

# Run the shell script and if any warnings, make fixes and re-run shell script until you receive "congratulations" message.

::✓ Lab2 logbook notes completed.

#Upload a screenshot of the proof listed above, the output file generated by the lab2-check.bash script, your log book, and your backupVM.py to blackboard.

= Practice For Quizzes, Tests, Midterm & Final Exam =

# List the steps to correctly restore your VMs from a USB disk to your c7host VM.

# How can you prompt the user for data and store into a variable?

# How do you perform mathematical operations in the Bash shell ~~and within a Bash shell script~~?

# What is the difference between a determinant loop and an in-determinant loop?

# Show a few examples how loops can be used to error-check when prompting the user for data.

~~# What is the purpose of the '''&&''' and '''||''' symbols when used with logic?'~~

# What does the command '''rpm -qi centos-release''' do and why is it important?

# What is the difference between '''rpm -q centos-release''' and '''uname -a'''?

Peter.callaghan

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OPS245 Lab 2

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