Changes

 The purpose of this lab is to discuss demonstrate how a Linux system administrator can monitor hard disk space availability, and to manage file system size via the Logical Volume Manager (LVM) application. This lab will also demonstrate how to manually mount (i.e. connect) and unmount (disconnect) partitions to file system directories, and demonstrate how to have partitions including adjusting the size of their automatically mounted to directories upon Linux systems if space is requiredsystem startup.

*[http://v1code.corenominaltutsplus.orgcom/howtotutorials/scheduling-setuptasks-awith-crontabcron-file/ jobs--net-8800 Using crontab]

<li>Click on '''Logical View''' (i.e. above home, root, swap) and then click '''Create New Logical Volume''' button. What happens? Why do you think this happened?<br><br>We will now create another partition ('''/dev/vda3''') using the '''fdisk''' utility, format this newly-created partition so we can create another logical volume called '''archive'''.<br><br> </li>

<li>In the terminal as root, issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">fdisk ls /dev/vdavd*</span></code></b><br><br>Remember that we are using a Virtual Machine'''NOTE:''' If nothing displays, so issue the hard disk appears as command: '''ls /dev/vdasd*''' and use that device pathname ''' instead of /dev/sda''' instead.<br><br> <li>Issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">fdisk /dev/vda</span></code></b><br>(or ''fdisk /dev/sda'' if the previous command didn't work)</li>

<li>Open a terminal as root, and format your newly-created partition by issuing the command: <b><code><span style="color:#3366CC;font-size:1.2em;">mkfs -t ext4 /dev/vda3</span></code></b><br>(or ''mkfs -t ext4 /dev/sda3'')</li>

<li value="2021">'''Restart the system-config-lvm utility'''. Do you see a new /dev/sda3 partition under Physical Volumes?</li> <li>To add the newly created partition, you need to add it into LVM to be used. '''Exit the system-config-lvm utility''' and '''issue the following command to add the partition into LVM:'''<br><b><code><span style="color:#3366CC;font-size:1.2em;">pvcreate /dev/vda3</span></code></b> (or ''pvcreate /dev/sda3'' ) (enter '''y''' to proceed - ignore warning)</li>

Let's say that you have run out of disk space on your '''centos3''' VM, and you need more space on the root file-system, perhaps in order to host more webpages web-pages, or to support a larger database or new software. What are your options? Getting a replacement hard-drive would probably require re-installation of the operating system and backup/restore of or backing up and restoring data on the dataold hard disk.

Because we're using LVM we can avoid this problem. We can '''add a new <u>virtual</u> hard-drive''' (which will serve as a physical volume) to the volume group, and extend the root logical volume to make use of the new available space. Creating virtual hard drives is not only inexpensive, but a great way for students to learn now to simulate growing the size of the file system.

<li>At the top of your VM window (make certain <u>not</u> full screen mode) click the '''view ''' menu and change view from '''Console''' to <u>Details</u>''' .</li> <li>At the bottom left-hand corner, click '''Add Hardware''' and add a new storage device of '''2GBs''', make sure the '''Bus type''' is selected as: '''VirtIO disk'''.<br><br>'''NOTE: Make certain to click "select managed or other existing storage", and fill in the pathname circled in red as shown in the diagram on the right-hand-side.<br><br>'''</li>

<li>Use '''fdisk''' (''refer to how to use in Part 1'') to create a new single primary partition for '''/dev/vdb''' that fills the entire disk, save partition table (accepting defaults prompts would work), restart your '''centos3''' VM and then '''format''' that partition for file type: '''ext4'''.</li>

:: <b><code><span style="color:#3366CC;font-size:1.2em;">vgextend ''name_of_volumegroup'' /dev/vdb1</span></code></b>

<li>Reduce the size of the '''lv_root''' partition by '''1GB''' by issuing the following command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">lvreduce ''name_of_volumegroup''/root lv_root --size -1G</span></code></b></li>Confirm that the file system has been reduced.</li><li>Increase the size of the '''lv_root''' partition by another '''1GB''' by issuing the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">lvextend ''name_of_volumegroup''/root lv_root --size +1G</span></code></b></li>Confirm that the file system can been increased.</li><li>Record the LVM Management commands in your lab log-book.</li>

We take for granted that a file-system must be mounted (for example the root partition) in order for a Linux system to be usable upon system start-up. This was create automatically for the '''/archive''' mount point automatically when we used the system-config-lvm utility in the previous investigation. We need to learn now to do this manually by editing or adding an entry in the ''/etc/fstab'' file. The '''/etc/fstab''' (file system table) contains entries to mount various file systems automatically upon start-up of the Linux system.

The Linux sys admin system administrator also has the ability to manually '''mount''' (connect) and '''un-mount''' (disconnect) partitions in order to perform maintenance on the file system (for example un-mounting the '''/home''' partition to install software and prevent users from logging in during that process).

# Perform this Part part in your '''centos2''' VM.# As you may recall in Part 1 of Investigation 1, we created another logical volume called lv_archive '''archive''' using the graphical application '''system-config-lvm'''. This logical volume should be mounted (connected) to our existing file-system (2GB).

# What is the purposed of issuing this command without arguments? Can you see the lv_archive partition'''/archive''' mount point?

# View and record the fields for the '''/archive''' mount in your lab logbook, and then issue the following command to reconnect or mount '''/archive''':<br><b><code><span style="color:#3366CC;font-size:1.2em;">mount &nbsp; -t ext4 &nbsp; /dev/''name_of_volumegroup'centos_centos2/archive &nbsp; /archive</span></code></b><br><br>'''NOTE:''' If you are having problem mounting, use the /dev pathname listing in your /etc/fstab file.<br><br># Confirm that this file-system has been properly mounted. Note: You could have also issue issued the command: '''mount -a''' to <u>automatically</u> mount the file-systems contained in the '''/etc/fstab''' file.<br><br>Tip: If you had to do manually configure /etc/fstab (eg. only in text-based mode - centos3), you could have issued the command(as root):<br> <b><code><span style="color:#3366CC;font-size:1.2em;">echo "/dev/centos_centos2/archive /archive ext4 defaults 1 12" >> /etc/fstab</span></code></b> <br>(although we don't need to do this, since it was already done).<br><br># '''A curious question''': If root needs to unmount the '''/home''' directory for maintenance (i.e. prevent regular users from logging in), but were forced we had to first login in graphically as a regular user, then open a terminal and su into '''to "root", isn''', then t our regular user still logged in so we wouldncan't be able to unmount un-mount the /home, since we are still logged indirectory?! ? How can we as a Linux System Administrator get around the problem (hint: you already learned it somewhere in lab3!!! Wow, using what we already taught can pay-off in the future ... lol!).

# The methods to monitor potential penetration to a Linux system are too numerous, and are taught in other coures (for example: SEC520). On method of monitoring potential penetration is to look for abnormally large files. Issue the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">find -P / -size +10000k100000k</span></code></b>

<li value="5">Quickly view the tutorial about the <b>[http://v1code.corenominaltutsplus.orgcom/howtotutorials/scheduling-setuptasks-awith-crontabcron-file/ jobs--net-8800 Using crontab]</b> file to understand the purpose of this

<ol><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''centos2''' VM:<blockquote><ul><li>'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </li><li>Contents of '''/etc/fstab''' file</li><li>Proof that '''/archive''' has been mounted</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''centos3''' VM:<blockquote><ul><li>Proof of virtual hard disk creation</li><li>'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </li></ul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''c7host''' Machine:<blockquote><ul><li>Proof of creation of the shell script: '''monitor-disk-space.bash'''</li><li>Crontab entry for '''root''' account</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> '''Lab5''' log-book filled out.</li></ol>

= Preparing for the = Practice For Quizzes , Tests, Midterm &amp; Final Exam ==

# How do you create a an LV?# How do you delete resize an LV?