= INVESTIGATION 1: BASIC NETWORK CONFIGURATION = OBJECTIVE & PREPARATION==In OPS235, you learned how to configure a virtual private network 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 (REVISITEDas opposed to DHCP) =.

Remember how you set up This lab is a <u>review</u> of the network interfaces in your virtual machines in OPS235? You're expected to know that ''"insidematerial from labs 6 ( [http://zenit.senecac.on.ca/wiki/index.php/OPS235_Lab_6_-out"'' by now_CentOS7#Part_4:_Configuring_VM_Network_Setup_via_Command_Line_.28centos3.29 CLI Network Configuration] ), but will also additional topics.

In OPS235, you learned how to configure a virtual private network via graphical applications for the '''centos1''' and '''centos2''' machines*[https://www.tty1. In the previous lab, you have created and cloned VMs that are textnet/blog/2010/ifconfig-ip-based only ('''like centos3''')comparison_en. All of the services that we are configuring in this course require a working network connection; therefore, it is very important that you know html ip vs ifconfig]*[https://www.digitalocean.com/community/tutorials/how -to set (preferable configure) -use-rsync-to-sync-local-and-remote-directories-on-a static IP address, default gateway, as well as your DNS server-vps rsync Howto]*[https://help.ubuntu.com/community/CronHowto Cron HowTo]

This lab is a <u>review</u> of the material from labs 6 ( [http== INVESTIGATION 1://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 show newer BASIC NETWORK CONFIGURATION (more efficientREVISITED) commands in the process.==

=== Checking Your Current Network Settings ===

In OPS235 , you've have used the '''ifconfig''' and '''route ''' commands. In this course we'll use the '''ip''' command instead (, so that you're welcome to use the old ll be familiar with both sets of commands but you're expected to know the new ones too).

# View the table below comparing ''older '' vs ''newer '' methods of obtaining network setting information for a Linux machine.

<tr> <td>Obtain Hostname</td><th>uname -n</th><th>Sameuname -n</th></tr> <tr> <td>See MAC cache</td><th>arp -n</th><th>ip neighbour</th></tr>

<ol><li value="2">Run the '''ifconfig''' command on your '''host''' machine. Check and record the IPADDR for your default (dhcp) network interface card (possibly eno1) and the virtual bridge.</li><li>Issue the '''ip address''' commands separatelycommand on your '''host''' machine to determine the IPADDR and GATEWAY information (refer to above chart). Do you notice any differences between their respective outputsHow are the result similar or different than the ifconfig command?</li><li>Repeat the same steps for other two sets of commands listed in Issue the tableifconfig command on your VMs.what happened?</li><li>Which commands do you prefer Use the '''ip''' command for your VMs to use?list the IPADDR and GATEWAY information.</li><li>Use 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 In your OPS235 course, you used a series of commands (Permanentifconfig, route, and nameserver) Network Setting Changes == If you change your to setup a temporary network settings using connection. You can use the commands ip command (a another command) in the previous section, a similar way to create a temporary network connection. The problem with this network connection method is that those changes will be lost if you restart your Linux machine, although you may want to do that to create a temporary network connection for troubleshooting purposes.

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''# Why do you think that previously issued command can be useful when you want to edit your exiting network settings?).# The name of the file that contains your persistent network settings has the following name format: <br>'''ifcfg-{''interfacename}'''''# Which filename file-name in your network-scripts directory do you think contains your current network settings?# View the contents of the file to see if it contains the IP ADDRESSaddress, subnet mask, and default gateway?.

== Set Except for your host machine, all the Virtual Machines in this course will have '''static IP addresses on vm1, vm2network configuration''' (as opposed to Automatic or DHCP). Sometimes, and vm3 ==you will be required to debug networking problems quickly by changing the network configuration of your VMs. 

Except <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="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''', all '''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 Virtual Machines files used and entries required and note them in this course will 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>'''static network configurationping''' (as opposed 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 Automatic 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 DHCP)reboot each VM, to verify that you can connect to the Internet with the new static IP network configuration.Sometimes, If you will be required cannot connect to debug networking problems quickly by changing the Internet, then check the network configuration of your VMsfile and make corrections until you have a workable network connection for each VM from boot-up.</ol>

Perform If you are uncertain how to perform those above-listed operations by member, take time to practice them.If everything works and you are comfortable with these operations then you may proceed to the following Steps:next section.

If # '''IS THE NETWORK ON VM PLUGGED 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 are uncertain how will need to check the NIC settings in the <u>'''virtual'''</u> machine details to perform those aboveview and confirm the appropriate network connection.# '''IS THE NETWORK ENABLED?''' This is a problem more common with virtual networks than physical networks. Check in:<br> '''VirtManager'''-> '''ConnectionDetails'''-listed operations > '''VirtualNetworks''' that your network is active.# '''DO YOU HAVE AN IP ADDRESS?''' Run '''ip address''' to check.# '''CAN YOU PING THE HOST BY IP?''' (by memberits internal IP address). If not - check all of the above, take time to practice themcheck if you have an IP address conflict, and check that your subnet mask is correct.# '''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 google.ca?''' Run '''host google.ca'''. If everything works 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 comfortable with these operations then you may proceed to the next sectionmost common problems.

== Linux 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 troubleshooting ==file, look and correct errors and restart your network interface connection.

# '''Is it plugged in?''' On a physical network you would check whether Perform the cable is plugged in and the link light is on on your network card. In a virtual network environment you don't have that - you'll need to check the NIC settings in the virtual machine details. In there it will tell you which virtual network your virtual network card is connected to.# '''Is it turned on?''' This is a problem more common with virtual networks than physical networks. Check in your VirtManager->ConnectionDetails->VirtualNetworks that your network is active.# '''Do you have an IP address?''' Run '''ip address''' to check.# '''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, check that your subnet mask is correct.# '''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 google.ca?''' Run '''host google.ca'''. If it doesn't come back with an IP address, and all of the above worked - check that your DNS server is configured correctly and that you can ping it.<br>There are a number of other problems that could prevent your network connection from functioning but the above are the most common problems.Following Steps:

<ol><li value="7">Move to your vm1 in order to perform the following trouble-shooting task:<ol type="a"><li>Use the '''wget''' command to download and run the following shell script:<br>[ link shell script here ]<br><br></li><li>after you have run that shell script, restart your vm1 machine.</li><li>Use the commands taught in this lab to confirm if your network connection is broken.</li><li>Carefully check your configuration to see if there is a change to your settings</li><li>Try to temporarily connect to the Internet</li><li>Edit your network settings file to make the changes permanent</li><li>Test your connectivity (including after a reboot of your vm1.<br><br></li></ol></li></ol><ol><li value="8">'''Note:''' You should 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 do. You can't have a working web server (or any other kind of server) if you don't have a working network connection.</li></ol>

= SSH Server == Managing Services ===

The default (SSH server should already be installed and often the only) way to administer a linux server is via SSH. Even running in your case where VMs. If it's not installed, you have a direct console can install '''openssh-server''' using yum.It is essential for CNS/CTY students to all your VM screens become comfortable managing services since you may find it helpful will need to connect constantly stop services, change their configuration, and start them for the configuration changes to your virtual machines using SSH (if nothing else - you can resize the terminal window)take effect in nearly every topic this semester, and for other courses involving Linux network management.

The SSH server should be installed and running in your VMs. If it's not installed - you can install '''openssh-server'Perform the following steps:'' using yum. Whether it is running or not - you should practice the following commands to make sure you know how to use them, you'll need them for nearly every topic this semester:

# Note the following [http://zenit.senecac.on.ca/wiki/index.php/Init_vs_systemd#systemd_Command_Usage systemctl] commands (refer to man pages or the Internet) to learn how to use and become comfortable using them.:

<ol><li value="2">Launch your '''vm2''' machine, loginto 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>Now, issue 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 next 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. === 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 &amp; 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 startupmachine'''.</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 &amp; 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.

=== SSH Keys Performing Full Backups ===[[Image:ssh_connection_explained.png|thumb|right|500px|A diagram explaining how public / Private keys work. Another term to represent this process is called '''PKI''' (Public/Private Key Infrastructure) ]]Using the magic of public key cryptography you can SSH to a linux machine without using a password. This topic is crucial - not only for this course but in the industry, SSH keys are used everywhere that linux servers are used.

Here's A full backup represents backing up of all of the files of a modified diagram from [http://sebastien.saunier.me/blog/2015/05/10/github-public-key-authentication.html Sébastien Saunier's blog] that's a simple illustration of how SSH key authentication works computer machine (the one in the blog post had our case, a significant error in it which I fixed in VM). A full backup should be performed at the version here):end of each lab or assignment working session.

[[Image:ssh_connection_explainedIn 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.png|800px]]

It's not a complete diagram but it helps see all ''Perform the parts of ssh key authentication in one place.following steps:'''

=== Public#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:/Private key pair ===/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'''.

This needs It is recommended to create a Bash shell script to be generated on and used on automate the backing up of ALL your '''client''' (the user/machine you're connecting '''from''')VMs in sequence. The private key is the equivalent of You can do this by running a for loop using a passwordlist for vm1, that's why it's private. And a private key is used by one uservm2, that's why it's stored in a user's ~/.ssh/ directoryand vm3 image file pathnames.

<ol><li value="5">Create the sub-directory '''/root/bin/'''</li><li>You generate should know how to create full backups of your VMs in your OPS235 course. Create a new keypair with this 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 (press enter for all the questionsqcow2 images and xml config files):.</li></ol>

You'll 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 up with ~/.ssh/id_rsa and ~/.ss/id_rsaof your lab session.pub - now you have a key pair you can use Learning to create shell scripts to automate routine tasks (such as backups) will be EXTREMELY useful for authenticationyour NDD430 course.

=== Public key on the server Performing Incremental Backups ===

If you An incremental backup is a backup of only files that have changed since the private key - you can prove last backup. In your case, it may be a good idea to someone who has perform incremental backups of your public key that you're really the owner of that public key. That's how ssh key authentication works, so the server needs to have you user's public key. You can copy it over manually and append the contents of your ~/.sshetc/id_rsa''' directory for your VMs upon startup.pub from We will be using the client to ~/.ssh/authorized_keys on the server, or you can issue this '''rsync''' command on the client to do perform incremental backups for all that for you:of your VMs.

ssh-copy-id -i ~'''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/id_rsaon our server and VMs. You are going to use your ''host machine'' to backup files from the ''virtual machines''.pub username@server

After that you can login without a password. But remember - keys are per user, not per machine. So this will only work with one user on '''Perform the client and one user on the server (the two users involved in running the command above).following steps:'''

= Backups ({{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. }}

You# Make certain that your '''vm1''' machine is running.# Make certain that you are logged in as '''root'''re going to use user on your host machine to backup files from the virtual machines. To make it simpler we won# On your '''host machine''t have any incremental backups and the backups will be automated so don't rely on these too much, but they may save you some time over run the many weeks in this course.following commands:

On <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 host run the following commands:vm1</source>

<source lang=bash>mkdir -p /backup/vm1rsync -avz 192'''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.168.x.2:/etc /backup/vm1/</source>

<ol><li value="4">If rsync asked prompts for a password - , make sure certain that you completed the '''SSH key''' section above, and that you assigned the keys part of for the lab<u>appropriate user</u><br>(in this case, for the '''root user for both the hostname and that youvm1'''re using !)</li><li>When the correct user. If you get a different error - perhaps rsync is not installed. What command runs correctly, you should see is all the files from vm1 being copied overto 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>

Create a new file in vm1Since your host machine and VMs are '''not continuously running''', '''you are not required to schedule to perform your FULL BACKUPS periodically'''s (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, and rerun rsync. Notice that only that file gets copied over.)

'''Cron ''' is a ''daemon - '' (i.e. a program that runs in the background). ItThe term ''"Cron"'' is short for '''Chronograph''' which was an old fashioned term for a '''stop watch''' or '''timer'''s . The role of '''Cron''' is to run tasks periodically. It can run tasks for the system (as root) or for a user (any including regular users). Every userhas a crontab (Cron Table). We'll get cron which is a list of tasks they want to run some backup scripts for usperiodically. You do not edit this file manually: instead, but first letyou edit this table using the command '''crontab -e'''s see how it works.Once you run the command, you will get an empty file where you have to insert a line like this:

Every user has a crontab - a list of tasks they want to run periodically. You edit this table using the command '''crontab -e'Perform the following steps:''. Once you run the command you'll get an empty file where you have to insert a line like this:

# 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:<prebr><source>10 * * * * * echo "Cron ran this job at: "`date` >> /tmp/cron.log</presource># 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.

Wait for {{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 minute to passgzip command, and check you should use the Bash shell script that /tmp/cron.log was created with the expected contents. You can also check /var/log/cron you were adviced to create in order to see what jobs were runbackup all of your VMs.}}

= Completing the lab = EXPLORATION QUESTIONS ==

* Each of # 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 VMs should now boot host machine.# List the steps to create a command prompt (no graphical interface), and should be using a '''persistent static IP addressnetwork connection''' for your vm1 machine to connect to your host machine. * Each of your VMs should have # List at least '''3 trouble-shooting techniques''' to check or verify a working network connection and from a vm to a static IP addresshost machine.* Each of your VMs should have an SSH server running# List at least '''5 reasons''' (from networking trouble-shooting) that can break a network connection.* You should be able # List the tools (commands) how to configure / stop / start the ssh from your host service.# Explain why it is important to know how to manage network services if you intend to each VM as configure ("tweak") the root user without a passwordservice.* Backups # Briefly explain the purpose of the three VMs'''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 ''' /etcbin/ directories are made automatically in the hostclean-out.bash''' every half day.* You have notes in # What is the purpose of using '''crontabs''' for backing up your labbook about what youvirtual machines've learned in this lab.data to your host machine?