When a format is specified in any of the qemu-img commands, the following format types may be used:
raw - Raw disk image format (default). This can be the fastest file-based format. If your file system supports holes (for example in ext2 or ext3 ), then only the written sectors will reserve space. Use
qemu-img info to obtain the real size used by the image or
ls -ls on Unix/Linux. Although Raw images give optimal performance, only very basic features are available with a Raw image. For example, no snapshots are available.
qcow2 - QEMU image format, the most versatile format with the best feature set. Use it to have optional AES encryption, zlib-based compression, support of multiple VM snapshots, and smaller images, which are useful on file systems that do not support holes . Note that this expansive feature set comes at the cost of performance.
Although only the formats above can be used to run on a guest virtual machine or host physical machine, qemu-img
also recognizes and supports the following formats in order to convert from them into either
format. The format of an image is usually detected automatically. In addition to converting these formats into
, they can be converted back from
to the original format. Note that the qcow2 version supplied with Red Hat Enterprise Linux 7 is 1.1. The format that is supplied with previous versions of Red Hat Enterprise Linux will be 0.10. You can revert image files to previous versions of qcow2. To know which version you are using, run
qemu-img info qcow2 [imagefilename.img]
command. To change the qcow version see Section 23.19.2, “Setting Target Elements”
bochs - Bochs disk image format.
cloop - Linux Compressed Loop image, useful only to reuse directly compressed CD-ROM images present for example in the Knoppix CD-ROMs.
cow - User Mode Linux Copy On Write image format. The
cow format is included only for compatibility with previous versions.
dmg - Mac disk image format.
nbd - Network block device.
parallels - Parallels virtualization disk image format.
qcow - Old QEMU image format. Only included for compatibility with older versions.
qed - Old QEMU image format. Only included for compatibility with older versions.
vdi - Oracle VM VirtualBox hard disk image format.
vhdx - Microsoft Hyper-V virtual hard disk-X disk image format.
vmdk - VMware 3 and 4 compatible image format.
vvfat - Virtual VFAT disk image format.