The lvcreate command is used to create logical volumes in an existing volume group. A volume group is a collection of logical and physical volumes. This command allows us to allocate space from the volume group and create a new logical volume.

Use case 1: Create a logical volume of 10 gigabytes in the volume group vg1

Code:

lvcreate -L 10G vg1

Motivation: This use case is helpful when we want to allocate a specific amount of space for a logical volume. In this example, we allocate 10 gigabytes of space in the volume group vg1.

Explanation:

• lvcreate - The command to create a logical volume.
• -L 10G - Specifies the size of the logical volume. In this case, we use “10G” to indicate 10 gigabytes.
• vg1 - The volume group name in which the logical volume will be created.

Example output:

Logical volume "lvol0" created.

Use case 2: Create a 1500 megabyte linear logical volume named mylv in the volume group vg1

Code:

lvcreate -L 1500 -n mylv vg1

Motivation: This use case is useful when we want to create a logical volume with a specific size and name. In this example, we create a linear logical volume named “mylv” with a size of 1500 megabytes in the volume group vg1.

Explanation:

• lvcreate - The command to create a logical volume.
• -L 1500 - Specifies the size of the logical volume. In this case, we use “1500” to indicate 1500 megabytes.
• -n mylv - Specifies the name of the logical volume. In this case, we use “mylv”.
• vg1 - The volume group name in which the logical volume will be created.

Example output:

Logical volume "mylv" created.

Use case 3: Create a logical volume called mylv that uses 60% of the total space in volume group vg1

Code:

lvcreate -l 60%VG -n mylv vg1

Motivation: This use case is beneficial when we want to allocate a logical volume that utilizes a percentage of the total available space in the volume group. In this example, we allocate 60% of the total space in the volume group vg1 for the logical volume.

Explanation:

• lvcreate - The command to create a logical volume.
• -l 60%VG - Specifies the size of the logical volume relative to the total space in the volume group. In this case, we use “60%VG” to indicate 60% of the total space.
• -n mylv - Specifies the name of the logical volume. In this case, we use “mylv”.
• vg1 - The volume group name in which the logical volume will be created.

Example output:

Logical volume "mylv" created.

Use case 4: Create a logical volume called mylv that uses all the unallocated space in the volume group vg1

Code:

lvcreate -l 100%FREE -n mylv vg1

Motivation: This use case is used when we want to allocate all the unallocated space in the volume group for a logical volume. In this example, we allocate all the unallocated space in the volume group vg1 for the logical volume.

Explanation:

• lvcreate - The command to create a logical volume.
• -l 100%FREE - Specifies the size of the logical volume relative to the unallocated space in the volume group. In this case, we use “100%FREE” to indicate all the unallocated space.
• -n mylv - Specifies the name of the logical volume. In this case, we use “mylv”.
• vg1 - The volume group name in which the logical volume will be created.

Example output:

Logical volume "mylv" created.

Conclusion:

The lvcreate command is a powerful tool for creating logical volumes in an existing volume group. It allows us to specify the size, name, and utilization of space for logical volumes. By understanding the different use cases described above, you can effectively allocate space and create logical volumes based on your specific requirements.