vgdisplay Command Linux: Complete Guide to Display Volume Group Information

The vgdisplay command is an essential tool in Linux systems for displaying detailed information about Volume Groups (VGs) in Logical Volume Management (LVM). This powerful command provides administrators with comprehensive insights into storage configuration, helping manage disk space and monitor system resources effectively.

What is the vgdisplay Command?

The vgdisplay command stands for “Volume Group Display” and is part of the LVM2 package in Linux distributions. It shows detailed information about one or more volume groups, including size, allocation status, physical volumes, and logical volumes within the group.

Volume Groups act as storage pools that combine multiple physical volumes (hard drives or partitions) into a single logical unit, making storage management more flexible and efficient.

Basic Syntax and Usage

The basic syntax of the vgdisplay command is:

vgdisplay [options] [volume_group_name]

Simple Usage Example

To display information about all volume groups on the system:

sudo vgdisplay

Example output:

--- Volume group ---
VG Name               ubuntu-vg
System ID             
Format                lvm2
Metadata Areas        1
Metadata Sequence No  3
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                2
Open LV               2
Max PV                0
Cur PV                1
Act PV                1
VG Size               <19.00 GiB
PE Size               4.00 MiB
Total PE              4863
Alloc PE / Size       4863 / <19.00 GiB
Free PE / Size        0 / 0   
VG UUID               abc123-def4-5678-9abc-def012345678

Common Options and Parameters

Display Specific Volume Group

To view information about a specific volume group:

sudo vgdisplay ubuntu-vg

Short Format Display

Use the -s option for a concise summary:

sudo vgdisplay -s

Output:

"ubuntu-vg" <19.00 GiB [4863/0/0 free]
"data-vg" 50.00 GiB [12800/2560/10240 free]

Verbose Output

For more detailed information, use the -v option:

sudo vgdisplay -v ubuntu-vg

Colon-Separated Output

The -c option provides machine-readable output:

sudo vgdisplay -c

Output format:

ubuntu-vg:r/w:772:-1:0:2:2:-1:0:1:1:19922944:4096:4863:4863:0:abc123-def4-5678-9abc-def012345678

Understanding the Output Fields

Let’s break down the key fields displayed by vgdisplay:

Practical Examples and Use Cases

Example 1: Monitoring Storage Usage

Check available space in all volume groups:

sudo vgdisplay -s | grep -E "(Free|free)"

Example 2: Multiple Volume Groups

Display information for multiple volume groups:

sudo vgdisplay ubuntu-vg data-vg backup-vg

Example 3: JSON-like Output for Scripting

Use with other commands for automated monitoring:

sudo vgdisplay -c | awk -F: '{print $1 ": " $13*$14/1024/1024 " GB total, " $15*$14/1024/1024 " GB free"}'

Advanced Usage Scenarios

Integration with System Monitoring

Create a simple monitoring script:

#!/bin/bash
echo "Volume Group Status Report"
echo "=========================="
for vg in $(sudo vgs --noheadings -o vg_name); do
    echo "Checking VG: $vg"
    sudo vgdisplay -s $vg
    echo ""
done

Checking VG Health

Combine vgdisplay with other LVM commands:

sudo vgdisplay -v ubuntu-vg | grep -A 5 "Physical volumes"

Common Error Messages and Troubleshooting

Volume Group Not Found

If you encounter “Volume group not found” error:

sudo vgscan
sudo vgdisplay

Permission Denied

Always run vgdisplay with sudo privileges:

# Wrong
vgdisplay

# Correct
sudo vgdisplay

No Volume Groups Found

This indicates no LVM setup exists on the system. Check with:

sudo pvs
sudo vgs
sudo lvs

Related LVM Commands

The vgdisplay command works alongside other LVM tools:

• pvdisplay – Display physical volume information
• lvdisplay – Display logical volume information
• vgs – Brief volume group summary
• vgextend – Extend volume group size
• vgreduce – Reduce volume group size

Best Practices and Tips

Regular Monitoring

Include vgdisplay in regular system health checks:

sudo vgdisplay -s > /var/log/vg-status-$(date +%Y%m%d).log

Automation and Scripting

Use the colon-separated output for parsing in scripts:

VG_FREE=$(sudo vgdisplay -c ubuntu-vg | cut -d: -f16)
if [ "$VG_FREE" -lt 1000 ]; then
    echo "Warning: Low space in volume group"
fi

Documentation

Always document your volume group structure:

sudo vgdisplay -v > /docs/lvm-structure-$(hostname).txt

Performance Considerations

The vgdisplay command is generally lightweight, but consider these points:

• Use -s option for quick checks in scripts
• Avoid frequent verbose queries on systems with many volume groups
• Cache output when possible for repeated access

Security Implications

Volume group information can reveal storage architecture details:

• Restrict access to LVM commands to authorized users
• Use sudo for controlled access
• Be cautious when sharing vgdisplay output

Conclusion

The vgdisplay command is an indispensable tool for Linux system administrators working with LVM storage systems. It provides comprehensive volume group information essential for storage management, capacity planning, and troubleshooting. By mastering its various options and understanding the output format, administrators can effectively monitor and maintain their storage infrastructure.

Regular use of vgdisplay helps ensure optimal storage utilization, early detection of capacity issues, and informed decision-making for storage expansion or reorganization. Whether you’re managing a single server or a complex storage environment, vgdisplay remains a fundamental command in your Linux administration toolkit.