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→Generating a Public/Private Key Pair & Sharing the Public Key
= Basic = OBJECTIVE & PREPARATION==In OPS235, you learned how to configure a virtual private network configuration =for your '''vm1''', '''vm2''' and '''vm3''' virtual machines. You were required to configure a static network connection for your VMs. In OPS335, you will also be setting up a static network connection for all of your VMs (which all VMs will be text-based). All of the services that we 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).
== Check current settings INVESTIGATION 1: BASIC NETWORK CONFIGURATION (REVISITED) ==
<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: [ [https://wiki.cdot.senecacollege.ca/wiki/OPS235_Lab_6#Part_3:_Configuring_VM_Network_Setup_via_Command_Line_.28centos3_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>Set your IPADDR for each VM with the following rules:<ol type== Public"a"><li>Your IPADDR's third octet will use the last 2 digits in your student number.</li><li> Make certain that the 4th octet for your VMs does not start with '''1''' since that is reserved by your host machine.<br>Use the recommended fourth octets: '''2 for vm1''', '''3 for vm2''', and '''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: [ [https://wiki.cdot.senecacollege.ca/wiki/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:<ul><li>'''ping''' (what is the purpose of this command?). Try to ping google from your host machine.<br>Try to ping 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.</Private key pair ===ol>
'''Note:''' Youshould be able to go through that troubleshooting process pretty quickly. Setting up the network in this course is never a primary task, but it's almost always a prerequisite for anything else we're going to use your host machine to backup files from the virtual machinesdo. To make it simpler we wonYou can't have a working web server (or any incremental backups and the backups will be automated so other kind of server) if you don't rely on these too much, but they may save you some time over the many weeks in this coursehave a working network connection.
'''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. === SSH Key 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>The public key can be "shared" with other server accounts, and can be used in conjunction with your private key in order to help encrypt/de-crypt data. The diagram below is shared from [http://sebastien.saunier.me/blog/2015/05/10/github-public-key-authentication.html Sébastien Saunier's blog].It demonstrates how SSH key authentication works. It's not a complete diagram, but it helps see all the parts of ssh key authentication in one place. [[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 === The public/private key pair needs to be generated on and used on your '''host''' machine (i.e. the user/machine you're connecting '''from'''). The private key is the equivalent of a <u>''password''</u> (that is why it is considered to be <u>''private''</u> - only to be used by ''<u>one</u>'' owner). That is why the private key is stored in the owner's '''~/.ssh/''' directory. One very common mistake that students make is to either generate the key pair for the wrong account, or copy the public key to the wrong account on the intended remote machine. '''Perform the following Steps:''' # Make certain you are in your '''host''' machine.# You will be creating a '''key-pair on your host machine with no password''' (i.e. when generating keypair press enter for all prompts including the password).#Make certain you are logged on as '''root''' on your host machine.# Generate the key-pair by issuing the command:<br><source>ssh-keygen -t rsa</source> '''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. If you have the private key, you can prove to someone who has your public key that you are indeed the '''actual owner of that public key'''. That is how ssh key authentication works. You are then only required to transfer your public key to a remote server. <ol><li value="5">You are going to share the public key from the '''root user in your host machine''' with the '''root user of your vm1 machine'''.</li><li>Copy the contents of your '''~/.ssh/id_rsa.pub''' from your host machine and append to '''~/.ssh/authorized_keys''' on each of your Virtual Machines. In your case, you will issue the following command 3 times (for each vm IPADDR):<br><source>ssh-copy-id -i ~/.ssh/id_rsa.pub root@IPADDR_for_vm</source>'''NOTE:''' Press ENTER for all prompted information including the password (although this may seen counter-intuitive!).<br><br></li><li>Use the ssh command to test each ssh connection between your host and each virtual machine that you can connect to the VMs without having to use a password. This is essential to create backups from VMs to your hostmachine without being prompted for password.</li></ol> {{Admon/important|Errors in Copying Public Key from Host to VM|If you experience an error when copying the public key from your hostmachine to your VM, it is most likely caused from not permitting root login that you performed in the previous section. Set to allow login from root for each vm, restart your sshd service and then re-run the above command.}} After you perform either of those operations, you can then ssh into a remote vm without a password. '''NOTE:''' Always remember that these keys are '''per-user, <u>not</u> per machine'''. This means that sharing a user's public key will only work for that specific user. == INVESTIGATION 3: PERFORMING & AUTOMATING BACKUPS == 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). When performing labs or assignments in this class, if you fail to make backups and something bad occurs and there is loss of data, it only affects you. On the other hand, if you are supporting a client, or working for a company and fail to adequately perform backups and there is loss of data, then other users are affected by failure to backup essential data. === Performing Full Backups === A full backup represents backing up of all of the files of a computer machine (in our case, a VM). A full backup should be performed at the end of each lab or assignment working session. 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:''' #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 OPS235 lab2 on backing up your 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'''. 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 list for vm1, vm2, and vm3 image file pathnames. <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 run the shell script to verify that 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> It will be your responsibility as an administrator of your own Linux system, to backup all of your VMs for labs and assignments at the end of your lab session. Learning to create shell scripts to automate routine tasks (such as backups) will be EXTREMELY useful for your NDD430 course. === Performing Incremental Backups === An incremental backup is a backup of only files that have changed since the last backup. In your case, it may be a good idea to perform incremental backups of your '''/etc/''' directory for your VMs upon startup. We will be using the '''rsync''' command to perform incremental backups for 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''. '''Perform the following steps:''' {{Admon/important|Rsync Needs to be Installed on ALL VMs |Since you select minimum install on your VMs, the rsync command was not installed by default. You need the rsync command to be available on your host machine and all of your VMs. Make certain that the '''rsync''' command is installed on all your vms. }} # Make certain that your '''vm1''' machine is running.# Make certain that you are logged in as '''root''' user on your host machine.# On your '''host machine''', run the following commands: <source>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 denied for 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: '''Perform the following steps:''' # Refer to the following WIKI to learn how to use cron: [[crontab tutorial]]# In your host machine as root, modify the setting so it will run that echo command every minute by creating a crontab (via '''crontab -e''') entry with the following line:<br><source>* * * * * echo "Cron ran this job at: "`date` >> /tmp/cron.log</source># Save and exit your crontab edit session.# Wait for one minute to pass, and check the '''/tmp/cron.log''' file to see if it was created with the expected contents.<br>(You can also check '''/var/log/cron''' file to see what jobs were run).# Perform a Net-search to see how to configure that crontab entry to run every two minutes instead of every minute.# Edit your crontab entry to run same command every two minutes, save and exit, and then confirm by viewing '''/tmp/cron.log''' and '''/var/log/cron''' files.# Perform a Net-search to see how to run a cron for a command for every hour.# Edit your crontab to '''make automatic backups using the rsync command''' of the '''/etc''' directory from '''vm1''', '''vm2''', and '''vm3''' into '''/backup/incremental/vm1''', '''/backup/incremental/vm2''', and '''/backup/incremental/vm3''' every hour and overwrite the previous backup. {{Admon/important |Backup your VMs!|You MUST perform a '''full backup''' of ALL of your VMs whenever you complete your '''OPS335 labs''' or when working on your '''OPS335 assignments'''. You should be using the gzip command, and you should use the Bash shell script that you were adviced to create in order to backup all of your VMs.}} '''Record steps, commands, and your observations in INVESTIGATION 2 in your OPS335 lab log-book''' == COMPLETING THE LAB == ===Online Submission=== Follow the instructions for lab 1 on blackboard. <!--===Andrew's sections=== You may choose to:* Submit screenshots of your work on Blackboard, in which case you don't need to come to the lab.* Or come to the lab, show me your work, and talk to me about it. I want to hear what you've learned and answer any questions you have. You'll get the same grade regardless of how you choose to submit your work. Expected results of this lab are: ::<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 a working network connection and a static IP address.* ::<span style="color:green;font-size:1.5em;">✓</span> Each of your VMs should have an SSH server running.* You ::<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.* Backups ::<span style="color:green;font-size:1.5em;">✓</span> 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 : http://matrix.senecac.on.ca/~murray.saul/ops335/labcheck_network_backup.sh--> == EXPLORATION QUESTIONS == # Explain the major different between the '''ip''' and '''ifconfig''' commands.# List the steps to create a '''temporary static IP network connection''' for your vm1 machine to connect to your host machine.# List the steps to create a '''persistent static IP network connection''' for your vm1 machine to connect to your host machine.# List at least '''3 trouble-shooting techniques''' to check or verify a network connection from a vm to a host machine.# List at least '''5 reasons''' (from networking trouble-shooting) that can break a network connection.# List the tools (commands) how to configure / stop / start the ssh service.# Explain why it is important to know how to manage network services if you intend to configure ("tweak") the service.# Briefly explain the purpose of the '''tar''', '''cpio''', '''dump''', '''restore''' commands.# Explain how the '''rsync''' command differs from the ''tar'', ''cpio'', ''dump'', and ''restore'' commands.# List the steps to create a '''crontab''' entry to run the program '''/bin/clean-out.bash''' every half day.# What is the purpose of using '''crontabs''' for backing up your virtual machines' data to your host machine?