How to Use the Command 'vgchange' (with examples)

The vgchange command is a part of the Logical Volume Manager (LVM) system used in Linux, which allows administrators to manage disk storage in a more flexible and efficient manner. This command specifically focuses on changing the attributes of volume groups in the LVM system. With vgchange, you can activate or deactivate logical volumes, which means making them available or unavailable for use by the operating system. This can be particularly useful for managing disks in a variety of storage configurations and ensuring optimal performance and reliability.

Use case 1: Change the Activation Status of Logical Volumes in All Volume Groups

Code:

sudo vgchange --activate y|n

Motivation:

There are times when a system administrator needs to control the accessibility of all logical volumes within a Linux system, for example, during maintenance, upgrades, or troubleshooting. By activating or deactivating logical volumes across all volume groups, the admin can ensure that the necessary volumes are accessible or restricted as needed. This command provides a broad-stroke approach to managing the volume groups, delivering a quick method to globally enable or disable logical volumes.

Explanation:

• sudo: This command requires root privileges to execute because it involves changing critical system configurations. The sudo prefix ensures that the command is run with the necessary permissions.

• vgchange: The base command that allows changes to be made on the volume group attributes.

• --activate: This option specifies the action to perform on the logical volumes. The ‘activate’ command tells the system to change the activation state.

• y|n: This part of the command requires either ‘y’ or ’n’ as an input. ‘y’ will activate (make available) all logical volumes, whereas ’n’ will deactivate (make unavailable) all logical volumes.

Example Output:

  3 logical volume(s) in volume group "vg0" now active
  2 logical volume(s) in volume group "vg1" now inactive

In this output, logical volumes in different groups have been either activated or deactivated based on the specified option.

Use case 2: Change the Activation Status of Logical Volumes in the Specified Volume Group

Code:

sudo vgchange --activate y|n volume_group

Motivation:

In scenarios where you need more granular control—perhaps while working with specific storage pools or when only certain resources need to be modified—changing the activation status of logical volumes in a specified volume group becomes essential. This approach can be employed during isolated volume group maintenance or when adjusting specific workloads to control IO demands on particular storage devices.

Explanation:

• sudo: Used here to gain the administrative authority necessary for modifying system-level configurations.

• vgchange: The root command for adjusting volume group attributes under LVM.

• --activate: Directive to switch the activity status of volumes within the chosen group.

• y|n: Indicator of the desired activation status; ‘y’ activates the volumes, ’n’ deactivates them.

• volume_group: A placeholder for the actual name of the volume group you intend to affect. You would replace this with the specific group identified beforehand (often determined via the vgscan command, which scans all disks for volume groups).

Example Output:

  1 logical volume(s) in volume group "my_vg" now active
  0 logical volume(s) in volume group "my_vg" now inactive

Here, depending on the input, logical volumes within the specified ‘my_vg’ volume group are activated or deactivated.

Conclusion:

The vgchange command offers powerful control over logical volumes in Linux by allowing system administrators to activate or deactivate these volumes either globally or within specified groups. These capabilities are essential for managing the disk storage system’s accessibility effectively, enabling smooth administration, maintenance, and system performance optimization in various environments. By understanding and using these examples, practitioners can leverage vgchange to meet their specific system requirements and ensure well-organized storage management.