The vgscan command is a crucial utility in Linux systems for scanning all disks to discover and identify Volume Groups (VGs) managed by the Logical Volume Manager (LVM). This tool is essential for system administrators to understand the LVM storage configuration and ensure that all available physical volumes are correctly recognized and associated with their respective volume groups.

Understanding Vgscan Functionality

vgscan probes the disks for LVM metadata. When it finds valid metadata, it updates the LVM cache, making the discovered volume groups and logical volumes available for use by other LVM commands. This process is fundamental for managing flexible storage solutions in Linux environments.

Common Vgscan Usage Examples

Scan All Physical Volumes for Volume Groups

The most basic usage of vgscan is to scan all available physical volumes to detect any existing volume groups. This command updates the LVM cache with the discovered information.

vgscan

Scan with Ignored Locking Failures

In certain scenarios, locking mechanisms might prevent a full scan. The --ignorelockingfailure option allows vgscan to proceed even if it encounters locking issues, which can be useful for troubleshooting or in complex storage setups.

vgscan --ignorelockingfailure

Read-Only Scan

To check for volume groups without making any changes to the LVM cache or metadata, you can use the --readonly option. This is helpful for auditing or verifying the current LVM configuration without altering it.

vgscan --readonly

Verbose Output

For more detailed information during the scanning process, the --verbose flag provides extensive output, showing each step vgscan takes. This is invaluable for diagnosing issues or understanding the scanning behavior.

vgscan --verbose

Debugging Information

To get even more in-depth diagnostic information, use the --debug option. This flag is typically used when trying to pinpoint complex problems with LVM metadata or disk scanning.

vgscan --debug

Force Re-read of Metadata and Create Nodes

The --mknodes option forces vgscan to re-read the metadata from all disks and also creates the necessary device nodes in /dev. This can be useful after significant storage changes or if the LVM cache is suspected to be out of sync.

vgscan --mknodes

External Resources

• Vgscan Man Page
• Red Hat LVM Volume Group Management
• IBM LVM Overview