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== OBJECTIVE & PREPARATION==
In OPS235, you learned how to configure a virtual private network for the your '''centos1vm1''', '''centos2vm2''' and '''centos3vm3''' virtual machines. All of the virtual machines in the You were required to configure a static network connection for your VMs. In OPS335 course , you will also be setting up a static network connection for labs and assignments all of your VMs (which all VMs will be '''CLI''' or '''"text-based"''' (just as centos3 was CLI for your OPS235 labs). All of the services that we are configuring install and configure for this course '''require a working network connection'''; therefore, it is very important that you know how to configure a network connection for your VMs, whether via command line for trouble-shooting purposes, or to create a persistent (permanent) network connection that uses static IP address (as opposed to DHCP).
This lab is a <u>review</u> of the material from labs 6 ( [http://zenit.senecac.on.ca/wiki/index.php/OPS235_Lab_6_-_CentOS7#Part_4:_Configuring_VM_Network_Setup_via_Command_Line_.28centos3.29 CLI Network Configuration] ), but will also additional topics.
*[https://www.tty1.net/blog/2010/ifconfig-ip-comparison_en.html ip vs ifconfig]
*[https://www.digitalocean.com/community/tutorials/how-to-use-rsync-to-sync-local-and-remote-directories-on-a-vps rsync Howto]
*[https://help.ubuntu.com/community/CronHowto Cron HowTo]
=== Checking Your Current Network Settings ===
In OPS235, you have used the deprecated '''ifconfig''' and '''route''' commands. In this course we'll use the '''ip''' command instead. You may , so that you'll be familiar with the deprecated ifconfig and route both sets of commands, but you are expected to know the newer ip command as well.
<tr> <td>Obtain Hostname</td><th>uname -n</th><th>uname -n</th></tr>
<tr> <td>See MAC cache</td><th>arp -n</th><th>ip neighbour</th></tr>
</table>
<ol><li value="2">Run the '''ifconfig''' and command on your '''ip addresshost''' commands in your c7host machine . Check and at least one of record the IPADDR for your VMsdefault (dhcp) network interface card (possibly eno1) and the virtual bridge. Do all of these commands work both in the c7host and Virtual Machine? Do you notice any differences between their respective outputs?</li><li>Repeat Issue the same steps for the other set of ''older'ip''' command on your '' vs 'host'newer'' commands listed in machine to determine the tableIPADDR and GATEWAY information (refer to above chart).How are the result similar or different than the ifconfig command?</li><li>Which commands do you prefer to useIssue the ifconfig command on your VMs. what happened?</li><li>Use the '''ip''' command for your VMs to list the IPADDR and GATEWAY information.</li><li>Refer to the man pages or refer to following article [http://www.tecmint.com/ip-command-examples/ 10 Useful ip Commands] to see how to issue the above commands to create a <u>temporary</u> connection to your existing network.</ol>
=== Making Persistent (Permanent) Network Setting Changes ===
In order to have your network settings become permanent, you need to edit and save the settings changes in a file.
For the IP address, subnet mask, default gateway, and DNS server you edit that file is contained in a directory called: '''network-scripts'''.
'''Perform the following steps:'''
# From Change to the ''network-scripts'' directory (see your ''OPS335''/''OPS235''/''ULI101'' notes, issue a command to provide the full path-name of the directory: ''network-scripts''. If that command or utility does not exist, simply install it).
# The name of the file that contains your persistent network settings has the following name format:<br>'''ifcfg-''interfacename'''''
# Which file-name in your network-scripts directory do you think contains your current network settings?
Except for your host machine, all the Virtual Machines in this course will have '''static network configuration''' (as opposed to Automatic or DHCP).Sometimes, you will be required to debug networking problems quickly by changing the network configuration of your VMs.
<ol>
<li value="7">Edit the '''ifcfg-''interfacename''''' (most likely ifcfg-eth0) file for each of your VMs to use a static IP address (refer to previous OPS235 lab on networking: [ [httphttps://zenitwiki.senecaccdot.onsenecacollege.ca/wiki/index.php/OPS235_Lab_6_-_CentOS7OPS235_Lab_6#Part_4Part_3:_Configuring_VM_Network_Setup_via_Command_Line_.28centos328centos3_and_centos2.29 Network Config - CLI] ].<br> You should be configuring the BOOTPROTO ('''static ''' instead of dhcp), IPADDR, PREFIX (or NETMASK), GATEWAY, HWADDR, and DNS1 for this file. Note the following information for this setup:<ul><li>You Set your IPADDR for each VM with the following rules:<ol type="a"><li>Your IPADDR's third octet will be using your use the last 2 digits in your student number for .</li><li> Make certain that the third 4th octet in for your VMs does not start with '''1''' since that is reserved by your IPADDRhost machine. Your <br>Use the recommended fourth octets: '''2 for vm1 should use the first available address in the subnet''', '''3 for vm2 the second''', and vm3 the third. Make certain that the '''IPADDR does not interfere with the GATEWAY or DNS!4 for vm3'''.</li></ol></li><li>Don't forget to set the default gateway and DNS server for your VMs. You can use your host's IP address as a gateway and DNS server <br>(''libvirt'' will proxy the requests to the real DNS server).</li><li> You can refer to your previous lab to obtain information for setup of these options: [ [httphttps://zenitwiki.senecaccdot.onsenecacollege.ca/wiki/index.php/OPS335_Installation_Lab#Configuring_a_VM_host Configuring a VM Host] ]<br><br></li></ul><li>Make note of the files used and entries required and note them in your lab log-book.</li><li>Save your editing session, and then restart each VM and run the following command to ensure they still have the network configuration you set:</liul></olli> ::'''ping''' (what is the purpose of this command?). Try to ping matrix and google from your host machine. <br>Try to ping matrix and google from each of your VM's to ensure you can reach the outside world.::</li><li>'''ssh''' (into another server, like Matrix) </li></ul></li><li>After setting the network configuration for EACH VM, then either the the ifdown and ifup commands or reboot each VM, to verify that you can connect to the Internet with the new static IP network configuration. If you cannot connect to the Internet, then check the network configuration file and make corrections until you have a workable network connection for each VM from boot-up.</ol>
If the network works in your host, but not in your Virtual Machine, you should perform the following routine steps to troubleshoot the network connection:
# '''Is network on IS THE NETWORK ON VM plugged inPLUGGED IN?''' On a physical network you would check whether the cable is plugged in and the link light is on on your network card. In a virtual network environment, you don't have a physical network adapter. Instead, you will need to check the NIC settings in the <u>'''virtual'''</u> machine details to view and confirm the appropriate network connection.# '''Is the network enabledIS THE NETWORK ENABLED?''' This is a problem more common with virtual networks than physical networks. Check in your :<br> '''VirtManager'''->'''ConnectionDetails'''->'''VirtualNetworks''' that your network is active.# '''Do you have an DO YOU HAVE AN IP addressADDRESS?''' Run '''ip address''' to check.# '''Can you ping the host by CAN YOU PING THE HOST BY IP?''' (by its internal IP address). If not - check all of the above, check if you have an IP address conflict, and check that your subnet mask is correct.# '''Can you ping CAN YOU PING 8.8.8.8?''' If all of the above work - check that your default gateway is set correctly with '''ip route''' and that you can ping the default gateway.# '''Can you resolve CAN YOU RESOLVE google.ca?''' Run '''host google.ca'''. If the output doesn't provide an IP address, check that your DNS server is configured correctly and that you can ping that address.
There are a number of other problems that could prevent your network connection from functioning but the above are the most common problems.
==== "Run Script to Break My Network" script Connection for Troubleshooting ==== You will now download, set execute permissions and run a Bash shell script to try to "break" the network connection for your vm1. This will provide troubleshooting practice to check your network configuration file, look and correct errors and restart your network interface connection. Perform the Following Steps: #Move to your '''vm1''' machine and make certain that you are logged in as '''root'''.#Make certain that the '''wget''' command is available on your VM. If not, install the wget application. Make certain to do for ALL of your VMs.#Use the '''wget''' command (with option "--no-check-certificate" ) to download and run the following shell script:<br>http://scs.senecacollege.ca/~murray.saul/ops335/break-network.bash#When you have run that shell script, it should automatically restart your vm1.#Login to your vm1.#Use the commands taught in this lab to confirm if your network connection is broken.#Carefully check your configuration to see if there is a change to your settings#Try to temporarily connect to the Internet#Edit your network settings file to make the changes permanent#Test your connectivity (including after a reboot of your vm1)
::* '''systemctl status'''
<ol><li value="2">Launch your '''vm2''' machine, login to the machine, and open a shell terminal.</li><li>Use one of the commands above to check the status of your SSH server (i.e. service: ''sshd'').</li><li>Issue one of the above commands to stop of the ssh server and run a command to verify that the ssh server is no longer running.</li><li>Issue another one of the above commands to start the SSH server and to verify that it is running.</li><li>Issue a command (not listed above) to confirm that the ssh service will run upon when the vm2 server restarts(i.e. "enabled").</li></ol>
===Configuring the SSH Service===
A common (if somewhat blatant) way to try to hack into a machine is to try to ssh as '''root''' and brute-force root's password. The root user always exists, meaning the attacker doesn't need to try guessing what user names are on your system. If they can get access to root, they can do anything. To prevent this, we will edit the configuration file for the ssh service to prevent root from ssh'ing into your host machine. '''Perform the following steps:''' #Login to your Centos '''host''' machine for the following steps.#Use the more command to display '''/etc/ssh/sshd_config''' on your host. This file contains the configuration parameters for the ssh service.#Take a few moments to view this file. Lines that begin with # are comments. Either simple explanations of parameters, or parameters that have not been set.#Open the man page for '''sshd_config'''. This lists all the possible parameters in alphabetical order along with a brief explanation of what each one does. The parameter we are looking for is '''PermitRootLogin''', read its description.#Use a text editor to edit the file '''/etc/ssh/sshd_config''', and find the line that has '''PermitRootLogin'''. By default it is set to yes, allowing the root user to ssh in to the machine.# Uncomment '''PermitRootLogin''', and change the value to '''no'''.#Try to use ssh from one of your VMs to log into your host as root. What happened?#This is because (for most services) the '''changes you make to the configuration file will not take effect until the service restarts'''.#Restart the sshd service on your host and try to ssh in again. Now it should prevent you.#The option '''PermitRootLogin''' for '''all of your VMs''' for both labs and assignments MUST be set to '''yes'''. The reason for this is that you have created a virtual network, so you have protected the host from root login, so you don't have to do the same for your VMs. Also, by allowing root login for your VM's will allow you to automatically backup your VMs to your host machine (via a crontab entry) without being prompted for a root password for each VM. '''Note:''' Configuration files for most services follow a very similar format. Some use an = between the parameter and its value, some require you to group certain parameters together, and most use # to be a comment. You will get lots of experience working with the configuration files for services in this course. === Generating SSH KeysKey Concepts===
After performing lab7 in OPS235, you should have a basic understanding of ssh and public/private key cryptography to create secure connections between servers.<br>
[[Image:ssh_connection_explained.png|thumb|center|600px|A diagram explaining how public / Private keys work. Another term to represent this process is called '''PKI''' (Public/Private Key Infrastructure) ]]
<br />
Put this book on your "must-read" list. You can borrow a copy from the Toronto Public Library. I have yet to see a better introduction to encryption. It's not a reqirement for OPS335 - but if you want to not be clueless about security fundamentals online - read that book and understand it.
[[Image:crypto.jpeg|center|"crypto" by Steven Levy]]
=== Generating a Public/Private Key Pair & Sharing the Public Key ===
'''NOTE:''' When issuing this command, you will end up with the files: '''~/.ssh/id_rsa''' and '''~/.ssh/id_rsa.pub''' (private and public keys). So far, this topic is generally a repeat of OPS235 lab7. What you may '''<u>not</u>''' know is that by using a '''"trick"''' (the ''magic'' of public key cryptography), you can SSH to a Linux machine without using a password! Learning to perform this trick is <u>'''essential'''</u> in this course and in the industry in general. SSH keys are used everywhere that Linux servers are used.
After you perform either of those operations, you can then ssh into a remote vm without a password.
Data backups are considered to be an insurance policy. Running backup can be tedious, but they MUST be performed in an accurate and consistent basis, since loss of data can be expensive (For example: cost of hiring staff to re-enter data).
=== Performing Full Backups ===
In OPS235, you learned to use the command '''gzip''', '''gunzip''' (plus'''virsh dumpxml''' / '''virsh define''' if backing up to external storage device like a usb key) to backup your virtual machines. We will use the same method to perform a full backup for these labs and assignments.
'''Perform the following steps:'''
# Refer to the above notes to allow an ssh connection from Make certain that your virtual machines are NOT running.#Make certain that you are logged in as '''root''' user on your host machine .#Refer to any of OPS235 lab2 on backing up your Virtual Machines (VMs using the '''gzip''' command [https://wiki.cdot.senecacollege.ca/wiki/OPS235_Lab_2_-_CentOS7_-_HD2#Part_1:_Backing_Up_Virtual_Machines OPS235 Lab2 - Backing up VMs]#Make certain that you have performed a full backup for '''vm1''', '''vm2''', and '''vm3'') without requiring '. It is recommended to create a Bash shell script to automate the backing up of ALL your VMs in sequence. You can do this by running a for loop using a passwordlist for vm1, vm2, and vm3 image file pathnames.# Test each ssh connection between <ol><li value="5">Create the sub-directory '''/root/bin/'''</li><li>You should know how to create full backups of your VMs in your OPS235 course. Create a Bash shell script called:<br>'''/root/bin/fullbackup.bash''' that will backup all of your other vms (i.e. vm1, vm2, and vm3) one at a time using the '''gzip''' command to your host machine into the directory path-name: '''/backup/full/'''</li><li>Set execute permissions, and each virtual machine run the shell script to ensure verify that this you shell script works.</li><li>It is also recommended to backup to your USB key as well (qcow2 images and xml config files).</li></ol>
An incremental backup is a backup of only files that have changed since the last backup. In this labyour case, we will focus on it may be a method good idea to provide automatic perform incremental backups of your '''/etc/''' directory for your VMs to your host machine as opposed to performing full and incremental backups (although it is recommended to study these techniques since they may be useful at some point in a later lab, and will be useful in later courses)upon startup. We will now focus on be using the '''rsync ''' command to perform incremental backups for backing up our all of your VMs.
'''Rsync''' is a very versatile backup tool. As the name suggests, rsync is used for <u>synchronizing</u> files typically across a network. It works over the '''SSH''' protocol, which is useful in our situation since we are running ssh on our server and VMs. You are going to use your ''host machine'' to backup files from the ''virtual machines''.
# On your '''host machine''', run the following commands:
<source lang=bash>mkdir -p /backup/incremental/vm1rsync -avz 192.168.x.x:/etc /backup/incremental/vm1/ # where 192.168.x.x is the IPADDR of your vm1</source>
'''NOTE:''' This command will '''NOT ''' work if '''permit root access is deniedfor your VMs''' for your sshd service configuration, so keep it off for now...
<ol><li value="4">If rsync prompts for a password, make certain that you completed the '''SSH key''' section above, and that you assigned the keys for the <u>appropriate user</u><br>(in this case, for the '''root user for both the hostname and vm1'''!)</li><li>When the rsync command runs correctly, you should see all the files from vm1 being copied over to your host machine.</li><li>Run the rsync command again. Notice that the second time nothing is copied over to your host machine since none of the files have changed on your vm1 machine.</li><li>Create a new file in vm1's '''/etc/''' directory, and rerun '''rsync'''. Confirm on your '''host machine''' that only that file that was created on your vm1 machine actually got backed up to your host machine.</li><li>Repeat the above steps to create backups for your '''vm2''' and '''vm3''' machines on your host machine as well (for the respective directories: '''/backup/incremental/vm2''' and '''/backup/incremental/vm3''').</li></ol>
=== Automating Backups (cron) ===
Since your host machine and VMs are '''not continuously running''', '''you are not required to schedule to perform your FULL BACKUPS periodically''' (eg. every week at 2:00 AM). Instead, it will be YOUR responsibility to run your full backup script when you complete each of your OPS335 labs, or when you finish your OPS335 assignment working session. On the other hand, '''you will use cron to perform incremental backups''' (eg. copy updated files from the VMs/ /etc/ directory)
'''Cron''' is a ''daemon'' (i.e. a program that runs in the background). The term ''"Cron"'' is short for '''Chronograph''' which was an old fashioned term for a '''stop watch''' or '''timer'''. The role of '''Cron''' is to run tasks periodically. It can run tasks for the system (as root) or for a user (including regular users).Every user has a crontab (Cron Table) which is a list of tasks they want to run periodically. You do not edit this file manually: instead, you edit this table using the command '''crontab -e'''. Once you run the command, you will get an empty file where you have to insert a line like this:
'''Record steps, commands, and your observations in INVESTIGATION 2 in your OPS335 lab log-book'''
::<span style="color:green;font-size:1.5em;">✓</span> Each of your VMs should now boot to a command prompt (no graphical interface), and should be using a static IP address.
::<span style="color:green;font-size:1.5em;">✓</span> Each of your VMs should have an SSH server running.
::<span style="color:green;font-size:1.5em;">✓</span> should be able to ssh from your host to each VM as the root user without a password.
::<span style="color:green;font-size:1.5em;">✓</span> Backups Display contents of the three VMsbackup script called: ''' /etcroot/bin/fullbackup.bash'''::<span style="color:green;font-size:1.5em;">✓</ directories are made automatically in the hostspan> Full and incremental backups of your 3 VMs.::<span style="color:green;font-size:1.5em;">✓</span> You have notes in your labbook lab-book about what you've learned in this lab.::<span style="color:green;font-size:1.5em;">✓</span> Run a shell script to submit your lab:<br>:::'''Steps:''' :::*Issue the following command to download the bash shell script:<br>'''wget http://scsmatrix.senecac.senecacollegeon.ca/~andrewmurray.smithsaul/ops335/labcheck_network_backup.sh''':::*Assign execute permissions, and run the script to check your work:<br--> '''labcheck_network_backup.sh''':::*'''NOTE:''' When prompted for the network interface, use the '''virtual interface'''.
== EXPLORATION QUESTIONS ==