Logical Volume Management (LVM) is a device mapper target that provides logical volume management for the Linux kernel. It is a powerful and flexible system that allows you to manage your disk space more efficiently.

In this article, we will discuss how to create logical volumes, extend and reduce their sizes, remove them, and check detailed information about the various partitions and volume groups.

Creating a Logical Volume

The first step to creating a Logical Volume (LV) is to create a Physical Volume (PV) and then a Volume Group (VG).

1. Create a Physical Volume:

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sudo pvcreate /dev/sdb1

1. Create a Volume Group:

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sudo vgcreate myvg /dev/sdb1

1. Create a Logical Volume:

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sudo lvcreate -L 10G -n mylv myvg

The -L option specifies the size of the LV, and -n specifies the name. The myvg at the end is the name of the VG that the LV belongs to.

Extending a Logical Volume

If you find that you need more space on your LV, you can extend and --resizefs it with the following command:

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sudo lvextend -r -L+5G /dev/myvg/mylv

This command increases the size of the logical volume by 5GB.

Old technic to resize the filesystem after extending the logical volume:

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sudo resize2fs /dev/myvg/mylv

Reducing a Logical Volume

Before reducing the size of a logical volume, we need to reduce the filesystem first:

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sudo resize2fs /dev/myvg/mylv 10G

Then reduce the size of the LV:

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sudo lvreduce -L 10G /dev/myvg/mylv

This reduces the size of the logical volume to 10GB. Be cautious with this operation as it can lead to data loss if not handled properly.

Removing a Logical Volume

You can remove a logical volume with the lvremove command:

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sudo lvremove /dev/myvg/mylv

You’ll be asked to confirm the operation because it will destroy all data in the logical volume.

Checking Information about Partitions and Volume Groups

The pvs, vgs, and lvs commands display information about physical volumes, volume groups, and logical volumes, respectively.

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sudo pvs
sudo vgs
sudo lvs

The pvdisplay, vgdisplay, and lvdisplay commands provide more detailed information:

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sudo pvdisplay
sudo vgdisplay
sudo lvdisplay

These commands are essential for managing and understanding your LVM setup.

Logical Volume Management is a powerful tool in Linux. It provides a higher-level view of the disk storage on a computer system than the traditional view of disks and partitions. This flexibility is beneficial for system administrators who need to manage storage more effectively. It’s recommended to practice these commands and concepts in a safe environment to understand their potential fully.