backing file is missing or an incorrect format was specified) is an
error when ``-u`` is not used.
-qemu-img amend to adjust backing file (removed in 6.1)
-''''''''''''''''''''''''''''''''''''''''''''''''''''''
+``qemu-img amend`` to adjust backing file (removed in 6.1)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
The use of ``qemu-img amend`` to modify the name or format of a qcow2
backing image was never fully documented or tested, and interferes
before or after the remaining changes being performed by amend, as
appropriate.
-qemu-img backing file without format (removed in 6.1)
-'''''''''''''''''''''''''''''''''''''''''''''''''''''
+``qemu-img`` backing file without format (removed in 6.1)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''''
The use of ``qemu-img create``, ``qemu-img rebase``, or ``qemu-img
convert`` to create or modify an image that depends on a backing file
1) executables, which include:
- - Tools - qemu-img, qemu-nbd, qga (guest agent), etc
+ - Tools - ``qemu-img``, ``qemu-nbd``, ``qga`` (guest agent), etc
- - System emulators - qemu-system-$ARCH
+ - System emulators - ``qemu-system-$ARCH``
- - Userspace emulators - qemu-$ARCH
+ - Userspace emulators - ``qemu-$ARCH``
- Unit tests
access the files or devices the VM it's running on behalf of can access.
#### qemu-io model
-Qemu-io is a test harness used to test changes to the QEMU block backend
-object code. (e.g., the code that implements disk images for disk driver
-emulation) Qemu-io is not a device emulation application per se, but it
+``qemu-io`` is a test harness used to test changes to the QEMU block backend
+object code (e.g., the code that implements disk images for disk driver
+emulation). ``qemu-io`` is not a device emulation application per se, but it
does compile the QEMU block objects into a separate binary from the main
QEMU one. This could be useful for disk device emulation, since its
emulation applications will need to include the QEMU block objects.
QEMU binaries
~~~~~~~~~~~~~
-By default, qemu-system-x86_64 is searched in $PATH to run the guest. If there
-isn't one, or if it is older than 2.10, the test won't work. In this case,
+By default, ``qemu-system-x86_64`` is searched in $PATH to run the guest. If
+there isn't one, or if it is older than 2.10, the test won't work. In this case,
provide the QEMU binary in env var: ``QEMU=/path/to/qemu-2.10+``.
-Likewise the path to qemu-img can be set in QEMU_IMG environment variable.
+Likewise the path to ``qemu-img`` can be set in QEMU_IMG environment variable.
Make jobs
~~~~~~~~~
tests/image-fuzzer/runner.py -c '[["qemu-img", "info", "$test_img"]]' /tmp/test qcow2
-Alternatively, some command different from "qemu-img info" can be tested, by
+Alternatively, some command different from ``qemu-img info`` can be tested, by
changing the ``-c`` option.
Integration tests using the Avocado Framework
For comprehensive test results, please, set up your test environment
properly.
-Paths to binaries under test (SUTs) qemu-img and qemu-io are retrieved from
-environment variables. If the environment check fails the runner will
+Paths to binaries under test (SUTs) ``qemu-img`` and ``qemu-io`` are retrieved
+from environment variables. If the environment check fails the runner will
use SUTs installed in system paths.
-qemu-img is required for creation of backing files, so it's mandatory to set
+``qemu-img`` is required for creation of backing files, so it's mandatory to set
the related environment variable if it's not installed in the system path.
For details about environment variables see qemu-iotests/check.
using the orangepi_pc_defconfig. Also see https://buildroot.org for more information.
When using an image as an SD card, it must be resized to a power of two. This can be
-done with the qemu-img command. It is recommended to only increase the image size
+done with the ``qemu-img`` command. It is recommended to only increase the image size
instead of shrinking it to a power of two, to avoid loss of data. For example,
to prepare a downloaded Armbian image, first extract it and then increase
its size to one gigabyte as follows:
kilobytes. You can add an ``M`` suffix to give the size in megabytes and
a ``G`` suffix for gigabytes.
-See the qemu-img invocation documentation for more information.
+See the ``qemu-img`` invocation documentation for more information.
.. _disk_005fimages_005fsnapshot_005fmode:
|qemu_system| linux.img -hdb nbd+unix://?socket=/tmp/my_socket
-In this case, the block device must be exported using qemu-nbd:
+In this case, the block device must be exported using ``qemu-nbd``:
.. parsed-literal::
qemu-nbd --socket=/tmp/my_socket my_disk.qcow2
-The use of qemu-nbd allows sharing of a disk between several guests:
+The use of ``qemu-nbd`` allows sharing of a disk between several guests:
.. parsed-literal::
|qemu_system| linux1.img -hdb nbd+unix://?socket=/tmp/my_socket
|qemu_system| linux2.img -hdb nbd+unix://?socket=/tmp/my_socket
-If the nbd-server uses named exports (supported since NBD 2.9.18, or with QEMU's
+If the ``nbd-server`` uses named exports (supported since NBD 2.9.18, or with QEMU's
own embedded NBD server), you must specify an export name in the URI:
.. parsed-literal::
mkdir -m 0700 /tmp/keys
psktool -u rich -p /tmp/keys/keys.psk
-TLS-enabled servers such as qemu-nbd can use this directory like so::
+TLS-enabled servers such as ``qemu-nbd`` can use this directory like so::
qemu-nbd \
-t -x / \
.. option:: -S SIZE
Indicates the consecutive number of bytes that must contain only zeros
- for qemu-img to create a sparse image during conversion. This value is rounded
- down to the nearest 512 bytes. You may use the common size suffixes like
- ``k`` for kilobytes.
+ for ``qemu-img`` to create a sparse image during conversion. This value is
+ rounded down to the nearest 512 bytes. You may use the common size suffixes
+ like ``k`` for kilobytes.
.. option:: -t CACHE
suppressed from the destination image.
*SPARSE_SIZE* indicates the consecutive number of bytes (defaults to 4k)
- that must contain only zeros for qemu-img to create a sparse image during
+ that must contain only zeros for ``qemu-img`` to create a sparse image during
conversion. If *SPARSE_SIZE* is 0, the source will not be scanned for
unallocated or zero sectors, and the destination image will always be
fully allocated.
If the ``-n`` option is specified, the target volume creation will be
skipped. This is useful for formats such as ``rbd`` if the target
volume has already been created with site specific options that cannot
- be supplied through qemu-img.
+ be supplied through ``qemu-img``.
Out of order writes can be enabled with ``-W`` to improve performance.
This is only recommended for preallocated devices like host devices or other
If the option *BACKING_FILE* is specified, then the image will record
only the differences from *BACKING_FILE*. No size needs to be specified in
this case. *BACKING_FILE* will never be modified unless you use the
- ``commit`` monitor command (or qemu-img commit).
+ ``commit`` monitor command (or ``qemu-img commit``).
If a relative path name is given, the backing file is looked up relative to
the directory containing *FILENAME*.
Safe mode
This is the default mode and performs a real rebase operation. The
- new backing file may differ from the old one and qemu-img rebase
+ new backing file may differ from the old one and ``qemu-img rebase``
will take care of keeping the guest-visible content of *FILENAME*
unchanged.
exists.
Unsafe mode
- qemu-img uses the unsafe mode if ``-u`` is specified. In this
+ ``qemu-img`` uses the unsafe mode if ``-u`` is specified. In this
mode, only the backing file name and format of *FILENAME* is changed
without any checks on the file contents. The user must take care of
specifying the correct new backing file, or the guest-visible
sizes accordingly. Failure to do so will result in data loss!
When shrinking images, the ``--shrink`` option must be given. This informs
- qemu-img that the user acknowledges all loss of data beyond the truncated
+ ``qemu-img`` that the user acknowledges all loss of data beyond the truncated
image's end.
After using this command to grow a disk image, you must use file system and
supported. The common object types that it makes sense to define are the
``secret`` object, which is used to supply passwords and/or encryption
keys, and the ``tls-creds`` object, which is used to supply TLS
- credentials for the qemu-nbd server or client.
+ credentials for the ``qemu-nbd`` server or client.
.. option:: -p, --port=PORT
Expose the guest-visible contents of a qcow2 file via a block device
/dev/nbd0 (and possibly creating /dev/nbd0p1 and friends for
partitions found within), then disconnect the device when done.
-Access to bind qemu-nbd to an /dev/nbd device generally requires root
+Access to bind ``qemu-nbd`` to a /dev/nbd device generally requires root
privileges, and may also require the execution of ``modprobe nbd``
to enable the kernel NBD client module. *CAUTION*: Do not use
this method to mount filesystems from an untrusted guest image - a
Description
-----------
-qemu-storage-daemon provides disk image functionality from QEMU, qemu-img, and
-qemu-nbd in a long-running process controlled via QMP commands without running
-a virtual machine. It can export disk images, run block job operations, and
+``qemu-storage-daemon`` provides disk image functionality from QEMU,
+``qemu-img``, and ``qemu-nbd`` in a long-running process controlled via QMP
+commands without running a virtual machine.
+It can export disk images, run block job operations, and
perform other disk-related operations. The daemon is controlled via a QMP
monitor and initial configuration from the command-line.
By default the name of xattr's used by the client are passed through to the server
file system. This can be a problem where either those xattr names are used
by something on the server (e.g. selinux client/server confusion) or if the
-virtiofsd is running in a container with restricted privileges where it cannot
-access some attributes.
+``virtiofsd`` is running in a container with restricted privileges where it
+cannot access some attributes.
Mapping syntax
~~~~~~~~~~~~~~
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