Name of the hash algorithm to use for PBKDF algorithm Defaults to sha256. Name of the hash algorithm to use with the initialization vector generator (if required). Name of the initialization vector generator algorithm. Name of the cipher algorithm and key length. Provides the ID of a secret object that contains the passphrase ( encrypt.format=luks) or encryption key ( encrypt.format=aes). Support only remains in the command line utilities, for the purposes of data liberation and interoperability with old versions of QEMU. The use of this is no longer supported in system emulators. ![]() The original file must then be securely erased using a program like shred, though even this is ineffective with many modern storage technologies. The files must be cloned, using a different encryption passphrase in the new file. In the event of the passphrase being compromised there is no way to change the passphrase to protect data in any qcow images.A poorly chosen or short passphrase will compromise the security of the encryption. The user passphrase is directly used as the encryption key.This makes it vulnerable to chosen plaintext attacks which can reveal the existence of encrypted data. The AES-CBC cipher is used with predictable initialization vectors based on the sector number.This encryption format is considered to be flawed by modern cryptography standards, suffering from a number of design problems: The encryption key is given by the encrypt.key-secret parameter. If this is set to aes, the image is encrypted with 128-bit AES-CBC. LUKS encryption parameters can be tuned with the other encrypt.* parameters. The passphrase to use to unlock the LUKS key slot is given by the encrypt.key-secret parameter. If this is set to luks, it requests that the qcow2 payload (not qcow2 header) be encrypted using the LUKS format. This option is deprecated and equivalent to encrypt.format=aes encrypt.format Image format of the base image encryption backing_fileįile name of a base image (see create subcommand) backing_fmt Amongst others, this includes zero clusters, which allow efficient copy-on-read for sparse images. compat=1.1 enables image format extensions that only QEMU 1.1 and newer understand (this is the default). compat=0.10 uses the traditional image format that can be read by any QEMU since 0.10. Use it to have smaller images (useful if your filesystem does not supports holes, for example on Windows), zlib based compression and support of multiple VM snapshots.ĭetermines the qcow2 version to use. ![]() QEMU image format, the most versatile format. This data may or may not be zero, depending on the storage location. full mode preallocates space for image by writing data to underlying storage. falloc mode preallocates space for image by calling posix_fallocate(). Preallocation mode (allowed values: off, falloc, full). Use qemu-img info to know the real size used by the image or ls -ls on Unix/Linux. ![]() 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. This format has the advantage of being simple and easily exportable to all other emulators. This section describes each format and the options that are supported for it. This includes the preferred formats raw and qcow2 as well as formats that are supported for compatibility with older QEMU versions or other hypervisors.ĭepending on the image format, different options can be passed to qemu-img create and qemu-img convert using the -o option. QEMU supports many image file formats that can be used with VMs as well as with any of the tools (like qemu-img). QEMU block driver reference manual Description Disk image file formats
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