18.9. Supported qemu-img formats

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 on Linux or NTFS on Windows), 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 (no snapshots etc.).
  • 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 (non-NTFS file systems on Windows). 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 machine, qemu-img also recognizes and supports the following formats in order to convert from them into either raw , or qcow2 format. The format of an image is usually detected automatically. In addition to converting these formats into raw or qcow2 , they can be converted back from raw or qcow2 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 refer to Section 29.20.2, “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. It does not work with Windows.
  • 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.
  • vdi - Oracle VM VirtualBox hard disk image format.
  • vmdk - VMware 3 and 4 compatible image format.
  • vpc - Windows Virtual PC disk image format. Also referred to as vhd, or Microsoft virtual hard disk image format.
  • vvfat - Virtual VFAT disk image format.