vgdisplay

What is vgdisplay?

The vgdisplay command is a powerful tool within the LVM suite. It displays detailed information about a specified volume group (VG). A volume group is a collection of Physical Volumes (PVs) that are grouped together to create a larger pool of storage. Think of it as a container for your logical volumes (LVs), which are the actual partitions you use for data.

Without vgdisplay, navigating and understanding your LVM setup would be more difficult.

Basic Usage

The simplest form of vgdisplay is just typing the command itself:

sudo vgdisplay

This will display information about all volume groups on your system. The output will include details such as:

• VG Name: The name of the volume group.
• VG Size: The total size of the volume group.
• PE Size: The size of each Physical Extent (PE), which is the basic unit of storage within a VG.
• #PE: The total number of Physical Extents.
• Free PE: The number of free PEs available for creating new logical volumes.
• VG Status: The overall status of the volume group (e.g., active, inactive).

This provides a quick overview of your LVM configuration.

Displaying Information for a Specific Volume Group

To get information about a specific volume group, you need to provide the volume group name as an argument:

sudo vgdisplay myvg

Replace myvg with the actual name of your volume group. This command will only display information for myvg.

Understanding the Output

Let’s break down a sample output:

--- Volume group ---
VG Name               myvg
System ID             
Format                lvm2
Metadata Areas        1
Metadata Sequence No  2
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                1
Open LV               1
Max PV                0
Cur PV                2
Act PV                2
VG Size               <20.00 GiB
PE Size               4.00 MiB
Total PE              5120
Alloc PE / Size       1024 / <10.00 GiB
Free  PE / Size       4096 / <10.00 GiB
VG UUID               ... (UUID here)

This output tells us:

• The volume group is named myvg.
• It’s using the lvm2 format.
• It currently has 2 physical volumes.
• It has a total size of just under 20 GiB and 10 GiB are allocated.
• There are 4096 free PEs available.

Filtering Output with grep

For more specific information, combine vgdisplay with the grep command. For example, to only see the VG size:

sudo vgdisplay myvg | grep 'VG Size'

This will output only the line containing “VG Size.” You can filter this for any other piece of information displayed by vgdisplay.

Advanced Usage: Combining with other LVM commands

vgdisplay is often used in conjunction with other LVM commands, such as vgs, lvs, and pvs, to get a view of your storage configuration. For instance, after identifying a volume group of interest with vgs, you can use vgdisplay to drill down to see its specific details.

By mastering vgdisplay, you gain a tool in managing and troubleshooting your Linux system’s storage. Its straightforward syntax and detailed output make it an indispensable command for any system administrator.