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In this lesson, we're going to walk through

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how to manage logical volumes.

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So, up to this point,

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we'll work directly with the physical devices.

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However, there's a way to further abstract these items

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and use them in a more efficient way.

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Linux uses a process called device mapping

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to help us accomplish this.

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In Linux, device mapper creates the virtual devices

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and passes data from that virtual device

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to one or more physical devices.

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One major application of the device mapper

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is the Logical Volume Manager.

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If you recall when we configured our virtual machines,

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the storage option was defaulted for us to use LVM.

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LVM maps whole physical devices and partitions

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into one or more virtual containers

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called volume groups.

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Within these volume groups are one or more logical volumes.

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Ultimately, the logical volumes become the storage devices

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that the system, user, and the applications

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will end up working with.

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So, first thing we want to do, let's identify

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the current logical volumes that's on the system now.

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We'll do /dev/mapper.

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Again, from when we created the virtual machine,

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we see that the system created centos-root and centos-swap.

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Those are the logical volumes

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that we currently have on the system.

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Now, what we're going to do is we're going to scan the system

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for the current physical volumes,

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volume groups, and logical volumes.

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There's commands for those.

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Scan here.

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See we have one from the creation with CentOS?

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We're going to use the pvdisplay command.

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That's going to also show us

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a little bit more detailed information

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about the physical volumes that are currently on the system.

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Remember, the physical volumes are ones

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that has been identified and associated

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with the device mapper.

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You want to do the same thing, vgscan.

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See the volume groups that's currently created,

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only the CentOS.

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Then, I'm going to do the display.

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Again, showing us more information about the volume groups

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that are currently on the system.

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Last one will be the logical volume scan.

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Once more, logical volume display.

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Give us, again, more detailed information

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about the current logical volumes

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that are associated with the system.

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Now, we're going to hop right into creating

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the physical volumes.

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'Cause remember, we're going to layer this.

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So we're going to start with the physical volumes,

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then we're going to move to the volume groups,

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and then last the logical volumes.

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So let's start creating the physical volumes.

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So we want to do pvcreate.

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We want to use the hard disk that we used earlier

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that were partitioned.

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Sdb2.

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I partitioned these earlier.

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All right, looks like it's successfully created.

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Now, let's just verify that, pvdisplay.

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And now, we see we have the new physical volumes.

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Next, we're going to create a volume group

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from the physical volumes that we just created.

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New volume group create, going to need the backup.

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Going to use ones we just created,

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sdb1,

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/dev/sdb2.

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All right, so we have the volume group successfully created,

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so let's display that here.

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Do the quick one, the scan,

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and then we can also do the display command.

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All right, we see that it's created.

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The last thing we want to do is create three logical volumes

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to associate it with the new volume group.

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lvcreate.

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Create the name here.

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Going to do a system backup.

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Size,

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just going to give 'em all

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two gigabytes for now.

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And we're going to associate it with the backup volume group.

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Yep, going to accept this warning.

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All right, looks like that was successfully created.

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Going to do one more.

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Going to change the name to the data backup

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Created one more for the log.

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Wipe it.

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Okay.

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Now let's do a scan,

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and now we can see they we're all successfully created.

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Sometimes it will be necessary to extend

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or reduce the volume size

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and to do this you want to simply use

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the lvextend

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and the -l option,

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this is what the new size is going to be.

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So we're going to extend the data backup to three gigabytes.

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Okay?

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Dev,

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data backup.

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All right, looks like that went through.

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Next, we want to reduce the log backup file.

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So we'll do

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reduce again.

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Want to reduce it to one gig.

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Device backup.

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Log back.

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All right, we'll accept the warning here,

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and we'll see it successfully changed from two to one.

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So let's just verify this really quick.

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Do

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display,

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and now we can see that the log backup is one gigabyte

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and the data backup is three gigabytes now.

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The last thing we want to do is

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to create a file system on these volumes

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that we just created.

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So we'll do make file system, use .xfs for the first one.

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Dev,

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for the /systemback

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Okay, that went through successfully.

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Going to make a file system using .ext4.

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Going to use that for the data backup.

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Data backup.

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Okay, that's went through successfully.

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We'll do the same thing for the log system.

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So we're going to scroll up, change this to log.

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And looks like that went through as well.

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So to summarize, we went through creating fiscal volumes,

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volume groups, and logical volumes.

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We also created file systems on those volumes

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and now we can use them just

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like they were a regular hard disc.

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And I'll see you in the next lesson.