qemu-img

Create disk image with a specific size (in gigabytes)

$ qemu-img create [image_name.img] [gigabytes]G

$ qemu-img info [image_name.img]

$ qemu-img resize [image_name.img] [gigabytes]G

$ qemu-img map [image_name.img]

$ qemu-img convert -f [vmdk] -O [qcow2] [path/to/file/foo.vmdk] [path/to/file/foo.qcow2]

qemu-img command [options] [image format] filename [size]

create
    Creates a new disk image.

-f fmt
    Specifies the image format. Supported formats include raw, qcow2, vmdk, vdi, etc.

filename
    The path and name of the disk image to create or modify.

size
    The size of the disk image to create. Use suffixes like K, M, G, T for kilobytes, megabytes, gigabytes, and terabytes respectively.

convert
    Converts a disk image from one format to another.

-O output_fmt
    Specifies the output image format for conversion.

info
    Displays information about a disk image.

resize
    Resizes a disk image.

+size
    The amount to increase the image size by.

snapshot
    Manages snapshots of a disk image.

-c
    Create a new snapshot.

-l
    List existing snapshots.

-d
    Delete a snapshot.

-a
    Apply a snapshot.

commit
    Commit changes from a snapshot to the base image.

check
    Check a disk image for errors.

-r
    Reclaim unused space.

qemu-img is a command-line utility included with QEMU that allows you to create, convert, and manage virtual disk images. It supports a variety of image formats including raw, qcow2, vmdk, and vdi. You can use qemu-img to create new images, resize existing images, convert between formats, take snapshots, and perform other disk image manipulation tasks. This is crucial for virtualization as disk images represent the storage for virtual machines. Understanding qemu-img is critical to efficiently manage virtual machine storage. It's used extensively for creating virtual hard drives. It's an extremely versatile tool useful for managing virtual machine disk images for QEMU based virtual machines.

Resizing a disk image doesn't automatically resize the filesystem inside the image. You may need to use guest OS tools to resize the filesystem after resizing the image.
Some formats may support features like compression or encryption; explore format-specific options for these.

Create a 10GB qcow2 image: qemu-img create -f qcow2 mydisk.qcow2 10G
Convert a raw image to qcow2: qemu-img convert -O qcow2 old.raw new.qcow2
Get info about a qcow2 image: qemu-img info mydisk.qcow2

qemu-img was developed as part of the QEMU project, initially released in 2003.
Its evolution mirrors that of QEMU itself, with continuous improvements and support for newer disk image formats and features.
Over time, it became an essential tool for managing virtual machine storage, alongside the main QEMU emulator.

qemu-system-x86_64(1), virt-manager(1)