hwversion - Specify the vmdk virtual hardware version.
compat6 - Create a VMDK 6 image, instead of the default VMDK 4.
Recommended only if you are going to be switching through VMWare and QEMU frequently.
static - If set, the image will be created with metadata preallocation.Ī file format which is compatible with VMWare 3 and 4.
Recommended only if you are going to be switching through VirtualBox and QEMU frequently. This is the fastest option, and is recommended if you have a lot of disk space to spare.Ī file format which is also compatible with VirtualBox 1.1. if you formatted a file named raw with 2G as the size, it would take up 2 gigabytes of space on the disk. It is recommended to use qcow2 instead.Īs the name suggests - it is a "raw" file format, which means it will allocate all the space to the disk immediately, e.g. The main difference between the qcow2 and qcow file formats is that qcow2 supports multiple snapshots through a newer, flexible model for storing snapshots. This is an older version of the qcow2 file format. However it does have a minor speed loss compared to raw, but this is unnoticeable in normal use. It is fast, dynamically allocated, and has decent support in QEMU. QEMU can recognize and read several different file formats, but this section will list the ones you can create with qemu-img. Unrecommended unless you happen to have a supercomputer handy.įun Fact: The ext4 file system is capable of a maximum of 1.1529215 exabytes. Unrecommended unless you happen to have a supercomputer handy. For instance, 100G would be 100 gigabytes. You can also create hard disk images in pure megabytes if you want, e.g. For instance, 100M would be 100 megabytes. You can create hard disk images in pure kilobytes if you wanted, e.g. For instance, 100K would be 100 kilobytes. Of course modern operating systems take up much more than that, so it's recommended to make it at least 30 gigabytes or more, which can be done by replacing 100M with 30G.
100M - This specifies the size of the virtual disk.
It can be whatever, and have whatever extension (or none at all), it doesn't matter.
example.img - This specifies the name of the image we are going to be using.
There are many other file formats, which will be listed below. it only allocates space when needed, but at a (pretty much) unnoticeable speed loss. qcow2 is the recommended since it is dynamically allocated - e.g.
qcow2 - The file format we are using, in this case qcow2.
-f - An argument that specifies which file format we are going to be using.
This will be described in more detail later on. Other arguments include "dd", "info", "map", "measure", "snapshot", "rebase", and "resize".
create - This tells qemu-img that we are creating a disk image.
It is necessary for using the following command.
qemu-img - This is the name of the program.
It will create an output similar to this: Qemu-img create -f qcow2 example.img 100M Qemu -hda centos-cleaninstall.The standard command for creating a basic hard disk image is this. With the -snapshot flag, any changes made to the virtual machine while it is running are written to temporary files and thrown away when the virtual machine is turned off. QEMU also supports temporary snapshots, where the user does not have to explicitly create a separate. Use the qemu-img info command to determine an image's backing file.īacking file: centos-cleaninstall.img (actual path: centos-cleaninstall.img) Make sure to delete any snapshots before running and modifying the original image. Making any changes to a base image ( centos-cleaninstall.img in our example) will corrupt its snapshots. Instead delete the first snapshot image ( snapshot.img in our example), create another snapshot image of the base image as above, and start using the new. Making any changes to its backing file ( centos-cleaninstall.img) will corrupt this snapshot image.Ī snapshot image cannot be returned to its original state once modified. Qemu-img create -f qcow2 -b centos-cleaninstall.img snapshot.imgĪt this point, you would run QEMU against snapshot.img. The new image is now a read/write snapshot of the original image - any changes to snapshot.img will not be reflected in centos-cleaninstall.img. If you want to create a snapshot of an existing image called centos-cleaninstall.img, create a new QCow2 file using the -b flag to indicate a backing file. Snapshots in QEMU are images that refer to an original image using Redirect-on-Write to avoid changing the original image.
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