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===Part 2: Managing LVM Via Command Line & Adding Virtual Hard Drives===
[[Image:add_virtual_disk.png|thumb|400px|right|You can add virtual hard disks for a VM by changing to the '''Details''' section for the VM (as opposed to ''console''), click '''Add Hardware''', fill information in the '''Add New Virtual Hardware''' dialog box and clicking '''Finish'''.]]
Let's say that you have run out of disk space on your '''centos4centos3''' VM, and you need more space on the root file-system in order to host more web-pages, or to support a larger database. What are your options? Getting a replacement hard-drive would probably require re-installation of the operating system and/or backing up and restoring data on the old 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.
'''Perform the following operations to increase the size of lv_root in centos4centos3:'''
# Perform this Part in your '''centos4centos3''' VM.
# Run the following commands and make note of the output:
::<b><code><span style="color:#3366CC;font-size:1.2em;">ls /dev/vd*</span></code></b>
<li>Go back to the '''console''' view</li>
<li>Issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">ls /dev/vd*</span></code></b>, what has changed?</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 '''centos4centos3''' VM and then '''format''' that partition for file type: '''ext4'''.</li>
<li>Now we'll make the new device a '''physical volume''', add it to the '''volume group''', and extend '''lv_root''':</li>
</ol>
# Note the line that automatically mounts a file-system (''/dev/sda3'', type ''ext4'') to '''/archive'''. This was automatically performed for you via the '''system-config-lvm''' utility.
# 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 -t ext4 /dev/centos_centos2/archive /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 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 - centos4centos3), 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 2" >> /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 but we had to first login in graphically as a regular user, then su to "root", isn't our regular user still logged in so we can't un-mount the /home directory?!? 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!).
'''Perform the Following Steps:'''
# Make certain that your '''c7host''', '''centos2''', and '''centos4centos3''' VMs are running.
# Switch to your '''centos2''' VM, open a shell terminal, and issue the Linux command: <b><code><span style="color:#3366CC;font-size:1.2em;">wget http://matrix.senecac.on.ca/~murray.saul/ops235/lab5-check.bash</span></code></b>
# Give the '''lab5-check.bash''' file execute permissions (for the file owner).
# Run the shell script and if any warnings, make fixes and re-run shell script until you receive "congratulations" message.
#Arrange proof of the following on the screen:<br><blockquote><span style="color:green;font-size:1.5em;">✓</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><span style="color:green;font-size:1.5em;">✓</span> '''centos4centos3''' VM:<blockquote><ul><li>Proof of virtual hard disk creation</li><li>'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </li></ul></blockquote><span style="color:green;font-size:1.5em;">✓</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><span style="color:green;font-size:1.5em;">✓</span> '''Lab5''' log-book filled out.
