How to Use the Command 'lvcreate' (with Examples)

The lvcreate command is a critical tool in the Linux ecosystem for managing logical volumes within volume groups. Logical Volume Management (LVM) allows for flexible disk space allocation, enabling users to create and resize disk volumes without needing to unmount filesystems. This capability provides an advantage in environments where disk space requirements fluctuate, offering the ability for on-the-fly adjustments. The lvcreate utility specifically focuses on creating logical volumes within these groups, facilitating a vital component of disk space management.

Use Case 1: Creating a Logical Volume of 10 Gigabytes

Code:

lvcreate -L 10G vg1

Motivation:

Creating a fixed-size logical volume is a common task in environments where predictable storage space is necessary, such as when allocating initial space for a new application or database. By setting a specific size, system administrators can efficiently manage disk resources and ensure that specific applications have the necessary storage space while avoiding overuse of available disk resources in the volume group.

Explanation:

• -L 10G: This flag specifies the size of the logical volume. In this case, it is set to 10 gigabytes. The -L option is used to define a fixed size.
• vg1: This refers to the name of the volume group in which the logical volume will be created. The volume group acts as a storage pool from which logical volumes are allocated.

Example Output:

Logical volume "lvol0" created.

Use Case 2: Creating a 1500 Megabyte Linear Logical Volume Named ‘mylv’

Code:

lvcreate -L 1500 -n mylv vg1

Motivation:

When specific naming conventions are required for logical volumes, possibly for easier identification or organization within the system, naming a logical volume is crucial. Specifying the size in megabytes allows for greater precision, which can be necessary for applications whose storage requirements must be tailored to specific constraints.

Explanation:

• -L 1500: As with the first example, this flag sets the size of the logical volume, but this time in megabytes (MB).
• -n mylv: The -n flag allows the user to specify a name for the logical volume, in this case, ‘mylv’, which aids in identifying the purpose or type of data within the volume.
• vg1: Again specifies the volume group within which the logical volume will be created.

Example Output:

Logical volume "mylv" created.

Use Case 3: Creating a Logical Volume Called ‘mylv’ Using 60% of Total Space in Volume Group

Code:

lvcreate -l 60%VG -n mylv vg1

Motivation:

In scenarios where a specific proportion of the volume group’s space needs to be allocated, such as balancing space with other volumes or applications, using a percentage instead of a fixed size offers flexibility. This approach can be beneficial for dynamically maintaining storage capacities relative to the total available resources, enabling efficient resource utilization as requirements change over time.

Explanation:

• -l 60%VG: The -l flag enables allocation of space by percentage rather than a fixed size. The inclusion of %VG indicates that 60% of the total volume group’s free space will be allocated to the logical volume.
• -n mylv: Assigns the logical volume the name ‘mylv’, which helps in categorizing different volumes.
• vg1: Specifies the volume group that will provide the space for the new logical volume.

Example Output:

Logical volume "mylv" created.

Use Case 4: Creating a Logical Volume Called ‘mylv’ Using All Unallocated Space

Code:

lvcreate -l 100%FREE -n mylv vg1

Motivation:

Utilizing all remaining free space in a volume group can be advantageous when maximizing available storage is necessary, such as when consolidating data across multiple logical volumes or in situations where unallocated space needs to be put to immediate use. This operation effectively eliminates any wasted space in the volume group, making efficient use of resources.

Explanation:

• -l 100%FREE: Similar to the previous example, -l specifies the space allocation, but here, 100%FREE indicates that all currently unallocated space within the volume group will be used for the logical volume.
• -n mylv: Once again, this option assigns the logical volume a specific name for easy reference.
• vg1: Indicates the volume group being utilized to create the logical volume.

Example Output:

Logical volume "mylv" created.

Conclusion:

The lvcreate command is an essential part of managing logical volumes within the Linux environment, providing users and administrators the means to define storage space allocation in a flexible and dynamic manner. Through careful determination of size, name, and percentage allocation, precise control over disk resources is achieved, enhancing both storage organization and efficiency, especially in dynamic settings where requirements can change rapidly.