1923e9311SThomas Huth.. _disk images: 2324b2298SPaolo Bonzini 3324b2298SPaolo BonziniDisk Images 4324b2298SPaolo Bonzini----------- 5324b2298SPaolo Bonzini 6324b2298SPaolo BonziniQEMU supports many disk image formats, including growable disk images 7324b2298SPaolo Bonzini(their size increase as non empty sectors are written), compressed and 8324b2298SPaolo Bonziniencrypted disk images. 9324b2298SPaolo Bonzini 10324b2298SPaolo Bonzini.. _disk_005fimages_005fquickstart: 11324b2298SPaolo Bonzini 12324b2298SPaolo BonziniQuick start for disk image creation 13324b2298SPaolo Bonzini~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 14324b2298SPaolo Bonzini 15324b2298SPaolo BonziniYou can create a disk image with the command:: 16324b2298SPaolo Bonzini 17324b2298SPaolo Bonzini qemu-img create myimage.img mysize 18324b2298SPaolo Bonzini 19324b2298SPaolo Bonziniwhere myimage.img is the disk image filename and mysize is its size in 20324b2298SPaolo Bonzinikilobytes. You can add an ``M`` suffix to give the size in megabytes and 21324b2298SPaolo Bonzinia ``G`` suffix for gigabytes. 22324b2298SPaolo Bonzini 23*c5ba6219SPhilippe Mathieu-DaudéSee the ``qemu-img`` invocation documentation for more information. 24324b2298SPaolo Bonzini 25324b2298SPaolo Bonzini.. _disk_005fimages_005fsnapshot_005fmode: 26324b2298SPaolo Bonzini 27324b2298SPaolo BonziniSnapshot mode 28324b2298SPaolo Bonzini~~~~~~~~~~~~~ 29324b2298SPaolo Bonzini 30324b2298SPaolo BonziniIf you use the option ``-snapshot``, all disk images are considered as 31324b2298SPaolo Bonziniread only. When sectors in written, they are written in a temporary file 32324b2298SPaolo Bonzinicreated in ``/tmp``. You can however force the write back to the raw 33324b2298SPaolo Bonzinidisk images by using the ``commit`` monitor command (or C-a s in the 34324b2298SPaolo Bonziniserial console). 35324b2298SPaolo Bonzini 36324b2298SPaolo Bonzini.. _vm_005fsnapshots: 37324b2298SPaolo Bonzini 38324b2298SPaolo BonziniVM snapshots 39324b2298SPaolo Bonzini~~~~~~~~~~~~ 40324b2298SPaolo Bonzini 41324b2298SPaolo BonziniVM snapshots are snapshots of the complete virtual machine including CPU 42324b2298SPaolo Bonzinistate, RAM, device state and the content of all the writable disks. In 43324b2298SPaolo Bonziniorder to use VM snapshots, you must have at least one non removable and 44324b2298SPaolo Bonziniwritable block device using the ``qcow2`` disk image format. Normally 45324b2298SPaolo Bonzinithis device is the first virtual hard drive. 46324b2298SPaolo Bonzini 47324b2298SPaolo BonziniUse the monitor command ``savevm`` to create a new VM snapshot or 48324b2298SPaolo Bonzinireplace an existing one. A human readable name can be assigned to each 49324b2298SPaolo Bonzinisnapshot in addition to its numerical ID. 50324b2298SPaolo Bonzini 51324b2298SPaolo BonziniUse ``loadvm`` to restore a VM snapshot and ``delvm`` to remove a VM 52324b2298SPaolo Bonzinisnapshot. ``info snapshots`` lists the available snapshots with their 53324b2298SPaolo Bonziniassociated information:: 54324b2298SPaolo Bonzini 55324b2298SPaolo Bonzini (qemu) info snapshots 56324b2298SPaolo Bonzini Snapshot devices: hda 57324b2298SPaolo Bonzini Snapshot list (from hda): 58324b2298SPaolo Bonzini ID TAG VM SIZE DATE VM CLOCK 59324b2298SPaolo Bonzini 1 start 41M 2006-08-06 12:38:02 00:00:14.954 60324b2298SPaolo Bonzini 2 40M 2006-08-06 12:43:29 00:00:18.633 61324b2298SPaolo Bonzini 3 msys 40M 2006-08-06 12:44:04 00:00:23.514 62324b2298SPaolo Bonzini 63324b2298SPaolo BonziniA VM snapshot is made of a VM state info (its size is shown in 64324b2298SPaolo Bonzini``info snapshots``) and a snapshot of every writable disk image. The VM 65324b2298SPaolo Bonzinistate info is stored in the first ``qcow2`` non removable and writable 66324b2298SPaolo Bonziniblock device. The disk image snapshots are stored in every disk image. 67324b2298SPaolo BonziniThe size of a snapshot in a disk image is difficult to evaluate and is 68324b2298SPaolo Bonzininot shown by ``info snapshots`` because the associated disk sectors are 69324b2298SPaolo Bonzinishared among all the snapshots to save disk space (otherwise each 70324b2298SPaolo Bonzinisnapshot would need a full copy of all the disk images). 71324b2298SPaolo Bonzini 72324b2298SPaolo BonziniWhen using the (unrelated) ``-snapshot`` option 73324b2298SPaolo Bonzini(:ref:`disk_005fimages_005fsnapshot_005fmode`), 74324b2298SPaolo Bonziniyou can always make VM snapshots, but they are deleted as soon as you 75324b2298SPaolo Bonziniexit QEMU. 76324b2298SPaolo Bonzini 77324b2298SPaolo BonziniVM snapshots currently have the following known limitations: 78324b2298SPaolo Bonzini 79324b2298SPaolo Bonzini- They cannot cope with removable devices if they are removed or 80324b2298SPaolo Bonzini inserted after a snapshot is done. 81324b2298SPaolo Bonzini 82324b2298SPaolo Bonzini- A few device drivers still have incomplete snapshot support so their 83324b2298SPaolo Bonzini state is not saved or restored properly (in particular USB). 84324b2298SPaolo Bonzini 85324b2298SPaolo Bonzini.. include:: qemu-block-drivers.rst.inc 86