Changes

In OPS235, you learned how to configure a virtual private network for your '''centos1vm1''', '''centos2vm2''' and '''centos3vm3''' 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).

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.

For the IP address, subnet mask, default gateway, and DNS server you edit that file is contained in a directory called: '''network-scripts'''.

# 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).

<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>Set your IPADDR for each VM with the following rules:<ol type="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 for the '''GATEWAY''' or '''DNS'''by your host machine.<br>For example, Use the forth 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: [ [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:<ul><li>'''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>

#Test your connectivity (including after a reboot of your vm1.)

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.

[[Image:ssh_connection_explainedcrypto.png|thumbjpeg|center|600px|A diagram explaining how public / Private keys work. Another term to represent this process is called '''PKI''' (Public/Private Key Infrastructure) "crypto" by Steven Levy]]<br><br>

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 it 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 wrong account, or copy the public key to the WRONG wrong account on the intended remote machine.

# Generate the key-pair by issuing the command:<br><source lang="bash">ssh-keygen -t rsa</source>

'''NOTE:''' When issuing this command, you will end up with the files: '''~/.ssh/id_rsa''' and '''~/.ssssh/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.

<source lang=bash>mkdir -p /backup/incremental/vm1

# In your host machine as root, edit your crontab and enter the line above. Modify 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>

<!--===In Class Submission (Murray SaulAndrew's Classes only)sections===[[ImageYou may choose to:lab1_signoff.png|thumb|right|300px|Students should be prepared with * Submit screenshots of your work on Blackboard, in which case you don'''all required commands (system information) displayed in a terminal (or multiple terminals) prior t need to come to calling the instructor for signoff'''lab.]]'''Arrange evidence (command output) for each of these items on * Or come to the lab, show me your screenwork, then ask your instructor and talk to me about it. I want to review them hear what you've learned and sign off on 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's completionare:'''

::<span style="color:green;font-size:1.5em;">&#x2713;</span> FULL Full and INCREMENTAL incremental backups of your 3 VMs.

::<span style="color:green;font-size:1.5em;">&#x2713;</span> Run a shell script to submit your lab:<br>:::'''Steps:''' :::Issue the following command to download the bash shell script:<br>'''wget http://matrix.senecac.on.ca/~murray.saul/ops335/labcheck_network_backup.sh'''::::*Assign execute permissions, and run the script to check your work: '''labcheck_network_backup.sh'''::::*When prompted for the network interface, use the '''virtual bridge interface''' with IP 192.168.x.1 (where '''x''' is your last 2 digits of your student number).-->