How to Create and Manage LVM on Linux

Edited 2 weeks ago by ExtremeHow Editorial Team

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Logical Volume Management (LVM) is a way of allocating space on mass-storage devices that is more flexible than traditional partitioning. LVM is very useful for managing disk space in an efficient way. It allows users to easily resize partitions, add new ones, or move them around without the usual headaches of dealing with static partitions. This guide will help you step by step to understand how to create and manage LVM on a Linux system using simple commands.

Understanding LVM Components

Before creating and managing LVM, it is important to understand its components:

• Physical Volumes (PV): These are the raw disks or partitions that we will add to our volume group. You can think of them as the cornerstones on which everything else is built.
• Volume Groups (VG): These are essentially a collection of physical volumes. A volume group can contain one or more physical volumes.
• Logical Volumes (LV): These are the final products that we will use to create our file systems. Logical volumes are separated from the volume group and can be resized.

A step-by-step guide to creating and managing LVM

1. Install LVM tools

Before you start creating LVM, make sure that the LVM package (known as lvm2) is installed on your Linux system. You can check if it is installed by doing:

sudo lvm version

If it is not installed, you can install it using your distribution's package manager.

For Debian/Ubuntu:

sudo apt-get install lvm2

For Red Hat/CentOS:

sudo yum install lvm2

2. Create a physical volume (PV)

Physical volume is the first step. You need to create a PV from your available block storage devices. Here is a simple command for this:

sudo pvcreate /dev/sdb /dev/sdc

The above command initializes /dev/sdb and /dev/sdc as physical volumes.

3. Create a Volume Group (VG)

Next, you need to create a volume group consisting of your physical volumes. This is done using the vgcreate command:

sudo vgcreate my_vg /dev/sdb /dev/sdc

Here, we have created a volume group named my_vg that includes /dev/sdb and /dev/sdc.

4. Create a Logical Volume (LV)

Once you have your volume group, you can start creating logical volumes from it using lvcreate command:

sudo lvcreate -L 10G -n my_lv my_vg

This command creates a logical volume named my_lv with size 10 GB from the volume group my_vg.

5. Creating a file system on a logical volume

Now that you have a logical volume, you need to create a file system on it so that it can be used to store files. For example, to create an ext4 file system, you could run:

sudo mkfs.ext4 /dev/my_vg/my_lv

6. Mounting the Logical Volume

To use the space, you must mount the logical volume to a directory. You can do this as follows:

sudo mkdir /mnt/my_data sudo mount /dev/my_vg/my_lv /mnt/my_data

With this, your logical volume /dev/my_vg/my_lv is accessible at /mnt/my_data.

7. Resizing the Logical Volume

The biggest advantage of LVM is the ability to resize logical volumes. To increase a logical volume, first resize the volume:

sudo lvextend -L +5G /dev/my_vg/my_lv

Then, resize the file system to use the extra space:

sudo resize2fs /dev/my_vg/my_lv

To reduce the size (shrink) of a logical volume, you must first unmount it, then resize the file system, and then resize the logical volume:

sudo umount /mnt/my_data sudo e2fsck -f /dev/my_vg/my_lv sudo resize2fs /dev/my_vg/my_lv 8G sudo lvreduce -L 8G /dev/my_vg/my_lv sudo mount /dev/my_vg/my_lv /mnt/my_data

8. Deleting Logical Volumes, Volume Groups, and Physical Volumes

If you want to remove a logical volume in the future, you can first unmount it and then delete it:

sudo umount /mnt/my_data sudo lvremove /dev/my_vg/my_lv

To remove a volume group, make sure no logical volumes exist, and then use:

sudo vgremove my_vg

Finally, to delete a physical volume:

sudo pvremove /dev/sdb

Important Tips

• Back up important data: Always make sure you have a backup of important data before resizing or deleting a volume.
• Monitor LVM usage: Regularly check the status of your LVM setup using commands like lvdisplay, vgdisplay and pvdisplay.
• Choose the right file system: Depending on the workload and system requirements, choose the appropriate file system type (ext4, xfs, etc.).

Conclusion

Logical Volume Management (LVM) offers significant advantages over traditional partitioning in terms of flexibility, manageability, and efficiency. It proves particularly useful in managing disk space in servers and environments where storage needs change rapidly. By following the steps outlined here, along with regular maintenance practices, you can effectively manage your storage using LVM in a Linux environment.

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