1 [[chapter_virtual_machines]]
10 qm - Qemu/KVM Virtual Machine Manager
16 include::qm.1-synopsis.adoc[]
22 Qemu/KVM Virtual Machines
23 =========================
28 // http://pve.proxmox.com/wiki/Container_and_Full_Virtualization
29 // http://pve.proxmox.com/wiki/KVM
30 // http://pve.proxmox.com/wiki/Qemu_Server
32 Qemu (short form for Quick Emulator) is an open source hypervisor that emulates a
33 physical computer. From the perspective of the host system where Qemu is
34 running, Qemu is a user program which has access to a number of local resources
35 like partitions, files, network cards which are then passed to an
36 emulated computer which sees them as if they were real devices.
38 A guest operating system running in the emulated computer accesses these
39 devices, and runs as if it were running on real hardware. For instance, you can pass
40 an ISO image as a parameter to Qemu, and the OS running in the emulated computer
41 will see a real CD-ROM inserted into a CD drive.
43 Qemu can emulate a great variety of hardware from ARM to Sparc, but {pve} is
44 only concerned with 32 and 64 bits PC clone emulation, since it represents the
45 overwhelming majority of server hardware. The emulation of PC clones is also one
46 of the fastest due to the availability of processor extensions which greatly
47 speed up Qemu when the emulated architecture is the same as the host
50 NOTE: You may sometimes encounter the term _KVM_ (Kernel-based Virtual Machine).
51 It means that Qemu is running with the support of the virtualization processor
52 extensions, via the Linux KVM module. In the context of {pve} _Qemu_ and
53 _KVM_ can be used interchangeably, as Qemu in {pve} will always try to load the KVM
56 Qemu inside {pve} runs as a root process, since this is required to access block
60 Emulated devices and paravirtualized devices
61 --------------------------------------------
63 The PC hardware emulated by Qemu includes a mainboard, network controllers,
64 SCSI, IDE and SATA controllers, serial ports (the complete list can be seen in
65 the `kvm(1)` man page) all of them emulated in software. All these devices
66 are the exact software equivalent of existing hardware devices, and if the OS
67 running in the guest has the proper drivers it will use the devices as if it
68 were running on real hardware. This allows Qemu to runs _unmodified_ operating
71 This however has a performance cost, as running in software what was meant to
72 run in hardware involves a lot of extra work for the host CPU. To mitigate this,
73 Qemu can present to the guest operating system _paravirtualized devices_, where
74 the guest OS recognizes it is running inside Qemu and cooperates with the
77 Qemu relies on the virtio virtualization standard, and is thus able to present
78 paravirtualized virtio devices, which includes a paravirtualized generic disk
79 controller, a paravirtualized network card, a paravirtualized serial port,
80 a paravirtualized SCSI controller, etc ...
82 It is highly recommended to use the virtio devices whenever you can, as they
83 provide a big performance improvement. Using the virtio generic disk controller
84 versus an emulated IDE controller will double the sequential write throughput,
85 as measured with `bonnie++(8)`. Using the virtio network interface can deliver
86 up to three times the throughput of an emulated Intel E1000 network card, as
87 measured with `iperf(1)`. footnote:[See this benchmark on the KVM wiki
88 https://www.linux-kvm.org/page/Using_VirtIO_NIC]
91 [[qm_virtual_machines_settings]]
92 Virtual Machines Settings
93 -------------------------
95 Generally speaking {pve} tries to choose sane defaults for virtual machines
96 (VM). Make sure you understand the meaning of the settings you change, as it
97 could incur a performance slowdown, or putting your data at risk.
100 [[qm_general_settings]]
104 [thumbnail="screenshot/gui-create-vm-general.png"]
106 General settings of a VM include
108 * the *Node* : the physical server on which the VM will run
109 * the *VM ID*: a unique number in this {pve} installation used to identify your VM
110 * *Name*: a free form text string you can use to describe the VM
111 * *Resource Pool*: a logical group of VMs
118 [thumbnail="screenshot/gui-create-vm-os.png"]
120 When creating a virtual machine (VM), setting the proper Operating System(OS)
121 allows {pve} to optimize some low level parameters. For instance Windows OS
122 expect the BIOS clock to use the local time, while Unix based OS expect the
123 BIOS clock to have the UTC time.
125 [[qm_system_settings]]
129 On VM creation you can change some basic system components of the new VM. You
130 can specify which xref:qm_display[display type] you want to use.
131 [thumbnail="screenshot/gui-create-vm-system.png"]
132 Additionally, the xref:qm_hard_disk[SCSI controller] can be changed.
133 If you plan to install the QEMU Guest Agent, or if your selected ISO image
134 already ships and installs it automatically, you may want to tick the 'Qemu
135 Agent' box, which lets {pve} know that it can use its features to show some
136 more information, and complete some actions (for example, shutdown or
137 snapshots) more intelligently.
139 {pve} allows to boot VMs with different firmware and machine types, namely
140 xref:qm_bios_and_uefi[SeaBIOS and OVMF]. In most cases you want to switch from
141 the default SeaBIOS to OVMF only if you plan to use
142 xref:qm_pci_passthrough[PCIe pass through]. A VMs 'Machine Type' defines the
143 hardware layout of the VM's virtual motherboard. You can choose between the
144 default https://en.wikipedia.org/wiki/Intel_440FX[Intel 440FX] or the
145 https://ark.intel.com/content/www/us/en/ark/products/31918/intel-82q35-graphics-and-memory-controller.html[Q35]
146 chipset, which also provides a virtual PCIe bus, and thus may be desired if
147 one wants to pass through PCIe hardware.
156 Qemu can emulate a number of storage controllers:
158 * the *IDE* controller, has a design which goes back to the 1984 PC/AT disk
159 controller. Even if this controller has been superseded by recent designs,
160 each and every OS you can think of has support for it, making it a great choice
161 if you want to run an OS released before 2003. You can connect up to 4 devices
164 * the *SATA* (Serial ATA) controller, dating from 2003, has a more modern
165 design, allowing higher throughput and a greater number of devices to be
166 connected. You can connect up to 6 devices on this controller.
168 * the *SCSI* controller, designed in 1985, is commonly found on server grade
169 hardware, and can connect up to 14 storage devices. {pve} emulates by default a
170 LSI 53C895A controller.
172 A SCSI controller of type _VirtIO SCSI_ is the recommended setting if you aim for
173 performance and is automatically selected for newly created Linux VMs since
174 {pve} 4.3. Linux distributions have support for this controller since 2012, and
175 FreeBSD since 2014. For Windows OSes, you need to provide an extra iso
176 containing the drivers during the installation.
177 // https://pve.proxmox.com/wiki/Paravirtualized_Block_Drivers_for_Windows#During_windows_installation.
178 If you aim at maximum performance, you can select a SCSI controller of type
179 _VirtIO SCSI single_ which will allow you to select the *IO Thread* option.
180 When selecting _VirtIO SCSI single_ Qemu will create a new controller for
181 each disk, instead of adding all disks to the same controller.
183 * The *VirtIO Block* controller, often just called VirtIO or virtio-blk,
184 is an older type of paravirtualized controller. It has been superseded by the
185 VirtIO SCSI Controller, in terms of features.
187 [thumbnail="screenshot/gui-create-vm-hard-disk.png"]
189 [[qm_hard_disk_formats]]
192 On each controller you attach a number of emulated hard disks, which are backed
193 by a file or a block device residing in the configured storage. The choice of
194 a storage type will determine the format of the hard disk image. Storages which
195 present block devices (LVM, ZFS, Ceph) will require the *raw disk image format*,
196 whereas files based storages (Ext4, NFS, CIFS, GlusterFS) will let you to choose
197 either the *raw disk image format* or the *QEMU image format*.
199 * the *QEMU image format* is a copy on write format which allows snapshots, and
200 thin provisioning of the disk image.
201 * the *raw disk image* is a bit-to-bit image of a hard disk, similar to what
202 you would get when executing the `dd` command on a block device in Linux. This
203 format does not support thin provisioning or snapshots by itself, requiring
204 cooperation from the storage layer for these tasks. It may, however, be up to
205 10% faster than the *QEMU image format*. footnote:[See this benchmark for details
206 https://events.static.linuxfound.org/sites/events/files/slides/CloudOpen2013_Khoa_Huynh_v3.pdf]
207 * the *VMware image format* only makes sense if you intend to import/export the
208 disk image to other hypervisors.
210 [[qm_hard_disk_cache]]
213 Setting the *Cache* mode of the hard drive will impact how the host system will
214 notify the guest systems of block write completions. The *No cache* default
215 means that the guest system will be notified that a write is complete when each
216 block reaches the physical storage write queue, ignoring the host page cache.
217 This provides a good balance between safety and speed.
219 If you want the {pve} backup manager to skip a disk when doing a backup of a VM,
220 you can set the *No backup* option on that disk.
222 If you want the {pve} storage replication mechanism to skip a disk when starting
223 a replication job, you can set the *Skip replication* option on that disk.
224 As of {pve} 5.0, replication requires the disk images to be on a storage of type
225 `zfspool`, so adding a disk image to other storages when the VM has replication
226 configured requires to skip replication for this disk image.
228 [[qm_hard_disk_discard]]
231 If your storage supports _thin provisioning_ (see the storage chapter in the
232 {pve} guide), you can activate the *Discard* option on a drive. With *Discard*
233 set and a _TRIM_-enabled guest OS footnote:[TRIM, UNMAP, and discard
234 https://en.wikipedia.org/wiki/Trim_%28computing%29], when the VM's filesystem
235 marks blocks as unused after deleting files, the controller will relay this
236 information to the storage, which will then shrink the disk image accordingly.
237 For the guest to be able to issue _TRIM_ commands, you must enable the *Discard*
238 option on the drive. Some guest operating systems may also require the
239 *SSD Emulation* flag to be set. Note that *Discard* on *VirtIO Block* drives is
240 only supported on guests using Linux Kernel 5.0 or higher.
242 If you would like a drive to be presented to the guest as a solid-state drive
243 rather than a rotational hard disk, you can set the *SSD emulation* option on
244 that drive. There is no requirement that the underlying storage actually be
245 backed by SSDs; this feature can be used with physical media of any type.
246 Note that *SSD emulation* is not supported on *VirtIO Block* drives.
249 [[qm_hard_disk_iothread]]
252 The option *IO Thread* can only be used when using a disk with the
253 *VirtIO* controller, or with the *SCSI* controller, when the emulated controller
254 type is *VirtIO SCSI single*.
255 With this enabled, Qemu creates one I/O thread per storage controller,
256 rather than a single thread for all I/O. This can increase performance when
257 multiple disks are used and each disk has its own storage controller.
264 [thumbnail="screenshot/gui-create-vm-cpu.png"]
266 A *CPU socket* is a physical slot on a PC motherboard where you can plug a CPU.
267 This CPU can then contain one or many *cores*, which are independent
268 processing units. Whether you have a single CPU socket with 4 cores, or two CPU
269 sockets with two cores is mostly irrelevant from a performance point of view.
270 However some software licenses depend on the number of sockets a machine has,
271 in that case it makes sense to set the number of sockets to what the license
274 Increasing the number of virtual CPUs (cores and sockets) will usually provide a
275 performance improvement though that is heavily dependent on the use of the VM.
276 Multi-threaded applications will of course benefit from a large number of
277 virtual CPUs, as for each virtual cpu you add, Qemu will create a new thread of
278 execution on the host system. If you're not sure about the workload of your VM,
279 it is usually a safe bet to set the number of *Total cores* to 2.
281 NOTE: It is perfectly safe if the _overall_ number of cores of all your VMs
282 is greater than the number of cores on the server (for example, 4 VMs each with
283 4 cores (= total 16) on a machine with only 8 cores). In that case the host
284 system will balance the QEMU execution threads between your server cores, just
285 like if you were running a standard multi-threaded application. However, {pve}
286 will prevent you from starting VMs with more virtual CPU cores than physically
287 available, as this will only bring the performance down due to the cost of
290 [[qm_cpu_resource_limits]]
294 In addition to the number of virtual cores, you can configure how much resources
295 a VM can get in relation to the host CPU time and also in relation to other
297 With the *cpulimit* (``Host CPU Time'') option you can limit how much CPU time
298 the whole VM can use on the host. It is a floating point value representing CPU
299 time in percent, so `1.0` is equal to `100%`, `2.5` to `250%` and so on. If a
300 single process would fully use one single core it would have `100%` CPU Time
301 usage. If a VM with four cores utilizes all its cores fully it would
302 theoretically use `400%`. In reality the usage may be even a bit higher as Qemu
303 can have additional threads for VM peripherals besides the vCPU core ones.
304 This setting can be useful if a VM should have multiple vCPUs, as it runs a few
305 processes in parallel, but the VM as a whole should not be able to run all
306 vCPUs at 100% at the same time. Using a specific example: lets say we have a VM
307 which would profit from having 8 vCPUs, but at no time all of those 8 cores
308 should run at full load - as this would make the server so overloaded that
309 other VMs and CTs would get to less CPU. So, we set the *cpulimit* limit to
310 `4.0` (=400%). If all cores do the same heavy work they would all get 50% of a
311 real host cores CPU time. But, if only 4 would do work they could still get
312 almost 100% of a real core each.
314 NOTE: VMs can, depending on their configuration, use additional threads, such
315 as for networking or IO operations but also live migration. Thus a VM can show
316 up to use more CPU time than just its virtual CPUs could use. To ensure that a
317 VM never uses more CPU time than virtual CPUs assigned set the *cpulimit*
318 setting to the same value as the total core count.
320 The second CPU resource limiting setting, *cpuunits* (nowadays often called CPU
321 shares or CPU weight), controls how much CPU time a VM gets compared to other
322 running VMs. It is a relative weight which defaults to `100` (or `1024` if the
323 host uses legacy cgroup v1). If you increase this for a VM it will be
324 prioritized by the scheduler in comparison to other VMs with lower weight. For
325 example, if VM 100 has set the default `100` and VM 200 was changed to `200`,
326 the latter VM 200 would receive twice the CPU bandwidth than the first VM 100.
328 For more information see `man systemd.resource-control`, here `CPUQuota`
329 corresponds to `cpulimit` and `CPUWeight` corresponds to our `cpuunits`
330 setting, visit its Notes section for references and implementation details.
335 Qemu can emulate a number different of *CPU types* from 486 to the latest Xeon
336 processors. Each new processor generation adds new features, like hardware
337 assisted 3d rendering, random number generation, memory protection, etc ...
338 Usually you should select for your VM a processor type which closely matches the
339 CPU of the host system, as it means that the host CPU features (also called _CPU
340 flags_ ) will be available in your VMs. If you want an exact match, you can set
341 the CPU type to *host* in which case the VM will have exactly the same CPU flags
344 This has a downside though. If you want to do a live migration of VMs between
345 different hosts, your VM might end up on a new system with a different CPU type.
346 If the CPU flags passed to the guest are missing, the qemu process will stop. To
347 remedy this Qemu has also its own CPU type *kvm64*, that {pve} uses by defaults.
348 kvm64 is a Pentium 4 look a like CPU type, which has a reduced CPU flags set,
349 but is guaranteed to work everywhere.
351 In short, if you care about live migration and moving VMs between nodes, leave
352 the kvm64 default. If you don’t care about live migration or have a homogeneous
353 cluster where all nodes have the same CPU, set the CPU type to host, as in
354 theory this will give your guests maximum performance.
359 You can specify custom CPU types with a configurable set of features. These are
360 maintained in the configuration file `/etc/pve/virtual-guest/cpu-models.conf` by
361 an administrator. See `man cpu-models.conf` for format details.
363 Specified custom types can be selected by any user with the `Sys.Audit`
364 privilege on `/nodes`. When configuring a custom CPU type for a VM via the CLI
365 or API, the name needs to be prefixed with 'custom-'.
367 Meltdown / Spectre related CPU flags
368 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
370 There are several CPU flags related to the Meltdown and Spectre vulnerabilities
371 footnote:[Meltdown Attack https://meltdownattack.com/] which need to be set
372 manually unless the selected CPU type of your VM already enables them by default.
374 There are two requirements that need to be fulfilled in order to use these
377 * The host CPU(s) must support the feature and propagate it to the guest's virtual CPU(s)
378 * The guest operating system must be updated to a version which mitigates the
379 attacks and is able to utilize the CPU feature
381 Otherwise you need to set the desired CPU flag of the virtual CPU, either by
382 editing the CPU options in the WebUI, or by setting the 'flags' property of the
383 'cpu' option in the VM configuration file.
385 For Spectre v1,v2,v4 fixes, your CPU or system vendor also needs to provide a
386 so-called ``microcode update'' footnote:[You can use `intel-microcode' /
387 `amd-microcode' from Debian non-free if your vendor does not provide such an
388 update. Note that not all affected CPUs can be updated to support spec-ctrl.]
392 To check if the {pve} host is vulnerable, execute the following command as root:
395 for f in /sys/devices/system/cpu/vulnerabilities/*; do echo "${f##*/} -" $(cat "$f"); done
398 A community script is also available to detect is the host is still vulnerable.
399 footnote:[spectre-meltdown-checker https://meltdown.ovh/]
406 This reduces the performance impact of the Meltdown (CVE-2017-5754) mitigation
407 called 'Kernel Page-Table Isolation (KPTI)', which effectively hides
408 the Kernel memory from the user space. Without PCID, KPTI is quite an expensive
409 mechanism footnote:[PCID is now a critical performance/security feature on x86
410 https://groups.google.com/forum/m/#!topic/mechanical-sympathy/L9mHTbeQLNU].
412 To check if the {pve} host supports PCID, execute the following command as root:
415 # grep ' pcid ' /proc/cpuinfo
418 If this does not return empty your host's CPU has support for 'pcid'.
422 Required to enable the Spectre v1 (CVE-2017-5753) and Spectre v2 (CVE-2017-5715) fix,
423 in cases where retpolines are not sufficient.
424 Included by default in Intel CPU models with -IBRS suffix.
425 Must be explicitly turned on for Intel CPU models without -IBRS suffix.
426 Requires an updated host CPU microcode (intel-microcode >= 20180425).
430 Required to enable the Spectre V4 (CVE-2018-3639) fix. Not included by default in any Intel CPU model.
431 Must be explicitly turned on for all Intel CPU models.
432 Requires an updated host CPU microcode(intel-microcode >= 20180703).
440 Required to enable the Spectre v1 (CVE-2017-5753) and Spectre v2 (CVE-2017-5715) fix,
441 in cases where retpolines are not sufficient.
442 Included by default in AMD CPU models with -IBPB suffix.
443 Must be explicitly turned on for AMD CPU models without -IBPB suffix.
444 Requires the host CPU microcode to support this feature before it can be used for guest CPUs.
450 Required to enable the Spectre v4 (CVE-2018-3639) fix.
451 Not included by default in any AMD CPU model.
452 Must be explicitly turned on for all AMD CPU models.
453 This should be provided to guests, even if amd-ssbd is also provided, for maximum guest compatibility.
454 Note that this must be explicitly enabled when when using the "host" cpu model,
455 because this is a virtual feature which does not exist in the physical CPUs.
460 Required to enable the Spectre v4 (CVE-2018-3639) fix.
461 Not included by default in any AMD CPU model. Must be explicitly turned on for all AMD CPU models.
462 This provides higher performance than virt-ssbd, therefore a host supporting this should always expose this to guests if possible.
463 virt-ssbd should none the less also be exposed for maximum guest compatibility as some kernels only know about virt-ssbd.
468 Recommended to indicate the host is not vulnerable to Spectre V4 (CVE-2018-3639).
469 Not included by default in any AMD CPU model.
470 Future hardware generations of CPU will not be vulnerable to CVE-2018-3639,
471 and thus the guest should be told not to enable its mitigations, by exposing amd-no-ssb.
472 This is mutually exclusive with virt-ssbd and amd-ssbd.
477 You can also optionally emulate a *NUMA*
478 footnote:[https://en.wikipedia.org/wiki/Non-uniform_memory_access] architecture
479 in your VMs. The basics of the NUMA architecture mean that instead of having a
480 global memory pool available to all your cores, the memory is spread into local
481 banks close to each socket.
482 This can bring speed improvements as the memory bus is not a bottleneck
483 anymore. If your system has a NUMA architecture footnote:[if the command
484 `numactl --hardware | grep available` returns more than one node, then your host
485 system has a NUMA architecture] we recommend to activate the option, as this
486 will allow proper distribution of the VM resources on the host system.
487 This option is also required to hot-plug cores or RAM in a VM.
489 If the NUMA option is used, it is recommended to set the number of sockets to
490 the number of nodes of the host system.
495 Modern operating systems introduced the capability to hot-plug and, to a
496 certain extent, hot-unplug CPUs in a running system. Virtualization allows us
497 to avoid a lot of the (physical) problems real hardware can cause in such
499 Still, this is a rather new and complicated feature, so its use should be
500 restricted to cases where its absolutely needed. Most of the functionality can
501 be replicated with other, well tested and less complicated, features, see
502 xref:qm_cpu_resource_limits[Resource Limits].
504 In {pve} the maximal number of plugged CPUs is always `cores * sockets`.
505 To start a VM with less than this total core count of CPUs you may use the
506 *vpus* setting, it denotes how many vCPUs should be plugged in at VM start.
508 Currently only this feature is only supported on Linux, a kernel newer than 3.10
509 is needed, a kernel newer than 4.7 is recommended.
511 You can use a udev rule as follow to automatically set new CPUs as online in
515 SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1"
518 Save this under /etc/udev/rules.d/ as a file ending in `.rules`.
520 Note: CPU hot-remove is machine dependent and requires guest cooperation. The
521 deletion command does not guarantee CPU removal to actually happen, typically
522 it's a request forwarded to guest OS using target dependent mechanism, such as
530 For each VM you have the option to set a fixed size memory or asking
531 {pve} to dynamically allocate memory based on the current RAM usage of the
534 .Fixed Memory Allocation
535 [thumbnail="screenshot/gui-create-vm-memory.png"]
537 When setting memory and minimum memory to the same amount
538 {pve} will simply allocate what you specify to your VM.
540 Even when using a fixed memory size, the ballooning device gets added to the
541 VM, because it delivers useful information such as how much memory the guest
543 In general, you should leave *ballooning* enabled, but if you want to disable
544 it (like for debugging purposes), simply uncheck *Ballooning Device* or set
548 in the configuration.
550 .Automatic Memory Allocation
552 // see autoballoon() in pvestatd.pm
553 When setting the minimum memory lower than memory, {pve} will make sure that the
554 minimum amount you specified is always available to the VM, and if RAM usage on
555 the host is below 80%, will dynamically add memory to the guest up to the
556 maximum memory specified.
558 When the host is running low on RAM, the VM will then release some memory
559 back to the host, swapping running processes if needed and starting the oom
560 killer in last resort. The passing around of memory between host and guest is
561 done via a special `balloon` kernel driver running inside the guest, which will
562 grab or release memory pages from the host.
563 footnote:[A good explanation of the inner workings of the balloon driver can be found here https://rwmj.wordpress.com/2010/07/17/virtio-balloon/]
565 When multiple VMs use the autoallocate facility, it is possible to set a
566 *Shares* coefficient which indicates the relative amount of the free host memory
567 that each VM should take. Suppose for instance you have four VMs, three of them
568 running an HTTP server and the last one is a database server. To cache more
569 database blocks in the database server RAM, you would like to prioritize the
570 database VM when spare RAM is available. For this you assign a Shares property
571 of 3000 to the database VM, leaving the other VMs to the Shares default setting
572 of 1000. The host server has 32GB of RAM, and is currently using 16GB, leaving 32
573 * 80/100 - 16 = 9GB RAM to be allocated to the VMs. The database VM will get 9 *
574 3000 / (3000 + 1000 + 1000 + 1000) = 4.5 GB extra RAM and each HTTP server will
577 All Linux distributions released after 2010 have the balloon kernel driver
578 included. For Windows OSes, the balloon driver needs to be added manually and can
579 incur a slowdown of the guest, so we don't recommend using it on critical
581 // see https://forum.proxmox.com/threads/solved-hyper-threading-vs-no-hyper-threading-fixed-vs-variable-memory.20265/
583 When allocating RAM to your VMs, a good rule of thumb is always to leave 1GB
584 of RAM available to the host.
587 [[qm_network_device]]
591 [thumbnail="screenshot/gui-create-vm-network.png"]
593 Each VM can have many _Network interface controllers_ (NIC), of four different
596 * *Intel E1000* is the default, and emulates an Intel Gigabit network card.
597 * the *VirtIO* paravirtualized NIC should be used if you aim for maximum
598 performance. Like all VirtIO devices, the guest OS should have the proper driver
600 * the *Realtek 8139* emulates an older 100 MB/s network card, and should
601 only be used when emulating older operating systems ( released before 2002 )
602 * the *vmxnet3* is another paravirtualized device, which should only be used
603 when importing a VM from another hypervisor.
605 {pve} will generate for each NIC a random *MAC address*, so that your VM is
606 addressable on Ethernet networks.
608 The NIC you added to the VM can follow one of two different models:
610 * in the default *Bridged mode* each virtual NIC is backed on the host by a
611 _tap device_, ( a software loopback device simulating an Ethernet NIC ). This
612 tap device is added to a bridge, by default vmbr0 in {pve}. In this mode, VMs
613 have direct access to the Ethernet LAN on which the host is located.
614 * in the alternative *NAT mode*, each virtual NIC will only communicate with
615 the Qemu user networking stack, where a built-in router and DHCP server can
616 provide network access. This built-in DHCP will serve addresses in the private
617 10.0.2.0/24 range. The NAT mode is much slower than the bridged mode, and
618 should only be used for testing. This mode is only available via CLI or the API,
619 but not via the WebUI.
621 You can also skip adding a network device when creating a VM by selecting *No
625 If you are using the VirtIO driver, you can optionally activate the
626 *Multiqueue* option. This option allows the guest OS to process networking
627 packets using multiple virtual CPUs, providing an increase in the total number
628 of packets transferred.
630 //http://blog.vmsplice.net/2011/09/qemu-internals-vhost-architecture.html
631 When using the VirtIO driver with {pve}, each NIC network queue is passed to the
632 host kernel, where the queue will be processed by a kernel thread spawned by the
633 vhost driver. With this option activated, it is possible to pass _multiple_
634 network queues to the host kernel for each NIC.
636 //https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Tuning_and_Optimization_Guide/sect-Virtualization_Tuning_Optimization_Guide-Networking-Techniques.html#sect-Virtualization_Tuning_Optimization_Guide-Networking-Multi-queue_virtio-net
637 When using Multiqueue, it is recommended to set it to a value equal
638 to the number of Total Cores of your guest. You also need to set in
639 the VM the number of multi-purpose channels on each VirtIO NIC with the ethtool
642 `ethtool -L ens1 combined X`
644 where X is the number of the number of vcpus of the VM.
646 You should note that setting the Multiqueue parameter to a value greater
647 than one will increase the CPU load on the host and guest systems as the
648 traffic increases. We recommend to set this option only when the VM has to
649 process a great number of incoming connections, such as when the VM is running
650 as a router, reverse proxy or a busy HTTP server doing long polling.
656 QEMU can virtualize a few types of VGA hardware. Some examples are:
658 * *std*, the default, emulates a card with Bochs VBE extensions.
659 * *cirrus*, this was once the default, it emulates a very old hardware module
660 with all its problems. This display type should only be used if really
661 necessary footnote:[https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/
662 qemu: using cirrus considered harmful], for example, if using Windows XP or
664 * *vmware*, is a VMWare SVGA-II compatible adapter.
665 * *qxl*, is the QXL paravirtualized graphics card. Selecting this also
666 enables https://www.spice-space.org/[SPICE] (a remote viewer protocol) for the
668 * *virtio-gl*, often named VirGL is a virtual 3D GPU for use inside VMs that
669 can offload workloads to the host GPU without requiring special (expensive)
670 models and drivers and neither binding the host GPU completely, allowing
671 reuse between multiple guests and or the host.
673 NOTE: VirGL support needs some extra libraries that aren't installed by
674 default due to being relatively big and also not available as open source for
675 all GPU models/vendors. For most setups you'll just need to do:
676 `apt install libgl1 libegl1`
678 You can edit the amount of memory given to the virtual GPU, by setting
679 the 'memory' option. This can enable higher resolutions inside the VM,
680 especially with SPICE/QXL.
682 As the memory is reserved by display device, selecting Multi-Monitor mode
683 for SPICE (such as `qxl2` for dual monitors) has some implications:
685 * Windows needs a device for each monitor, so if your 'ostype' is some
686 version of Windows, {pve} gives the VM an extra device per monitor.
687 Each device gets the specified amount of memory.
689 * Linux VMs, can always enable more virtual monitors, but selecting
690 a Multi-Monitor mode multiplies the memory given to the device with
691 the number of monitors.
693 Selecting `serialX` as display 'type' disables the VGA output, and redirects
694 the Web Console to the selected serial port. A configured display 'memory'
695 setting will be ignored in that case.
697 [[qm_usb_passthrough]]
701 There are two different types of USB passthrough devices:
703 * Host USB passthrough
704 * SPICE USB passthrough
706 Host USB passthrough works by giving a VM a USB device of the host.
707 This can either be done via the vendor- and product-id, or
708 via the host bus and port.
710 The vendor/product-id looks like this: *0123:abcd*,
711 where *0123* is the id of the vendor, and *abcd* is the id
712 of the product, meaning two pieces of the same usb device
715 The bus/port looks like this: *1-2.3.4*, where *1* is the bus
716 and *2.3.4* is the port path. This represents the physical
717 ports of your host (depending of the internal order of the
720 If a device is present in a VM configuration when the VM starts up,
721 but the device is not present in the host, the VM can boot without problems.
722 As soon as the device/port is available in the host, it gets passed through.
724 WARNING: Using this kind of USB passthrough means that you cannot move
725 a VM online to another host, since the hardware is only available
726 on the host the VM is currently residing.
728 The second type of passthrough is SPICE USB passthrough. This is useful
729 if you use a SPICE client which supports it. If you add a SPICE USB port
730 to your VM, you can passthrough a USB device from where your SPICE client is,
731 directly to the VM (for example an input device or hardware dongle).
738 In order to properly emulate a computer, QEMU needs to use a firmware.
739 Which, on common PCs often known as BIOS or (U)EFI, is executed as one of the
740 first steps when booting a VM. It is responsible for doing basic hardware
741 initialization and for providing an interface to the firmware and hardware for
742 the operating system. By default QEMU uses *SeaBIOS* for this, which is an
743 open-source, x86 BIOS implementation. SeaBIOS is a good choice for most
746 Some operating systems (such as Windows 11) may require use of an UEFI
747 compatible implementation instead. In such cases, you must rather use *OVMF*,
748 which is an open-source UEFI implementation. footnote:[See the OVMF Project https://github.com/tianocore/tianocore.github.io/wiki/OVMF]
750 There are other scenarios in which the SeaBIOS may not be the ideal firmware to
751 boot from, for example if you want to do VGA passthrough. footnote:[Alex
752 Williamson has a good blog entry about this
753 https://vfio.blogspot.co.at/2014/08/primary-graphics-assignment-without-vga.html]
755 If you want to use OVMF, there are several things to consider:
757 In order to save things like the *boot order*, there needs to be an EFI Disk.
758 This disk will be included in backups and snapshots, and there can only be one.
760 You can create such a disk with the following command:
763 # qm set <vmid> -efidisk0 <storage>:1,format=<format>,efitype=4m,pre-enrolled-keys=1
766 Where *<storage>* is the storage where you want to have the disk, and
767 *<format>* is a format which the storage supports. Alternatively, you can
768 create such a disk through the web interface with 'Add' -> 'EFI Disk' in the
769 hardware section of a VM.
771 The *efitype* option specifies which version of the OVMF firmware should be
772 used. For new VMs, this should always be '4m', as it supports Secure Boot and
773 has more space allocated to support future development (this is the default in
776 *pre-enroll-keys* specifies if the efidisk should come pre-loaded with
777 distribution-specific and Microsoft Standard Secure Boot keys. It also enables
778 Secure Boot by default (though it can still be disabled in the OVMF menu within
781 NOTE: If you want to start using Secure Boot in an existing VM (that still uses
782 a '2m' efidisk), you need to recreate the efidisk. To do so, delete the old one
783 (`qm set <vmid> -delete efidisk0`) and add a new one as described above. This
784 will reset any custom configurations you have made in the OVMF menu!
786 When using OVMF with a virtual display (without VGA passthrough),
787 you need to set the client resolution in the OVMF menu (which you can reach
788 with a press of the ESC button during boot), or you have to choose
789 SPICE as the display type.
792 Trusted Platform Module (TPM)
793 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
795 A *Trusted Platform Module* is a device which stores secret data - such as
796 encryption keys - securely and provides tamper-resistance functions for
797 validating system boot.
799 Certain operating systems (such as Windows 11) require such a device to be
800 attached to a machine (be it physical or virtual).
802 A TPM is added by specifying a *tpmstate* volume. This works similar to an
803 efidisk, in that it cannot be changed (only removed) once created. You can add
804 one via the following command:
807 # qm set <vmid> -tpmstate0 <storage>:1,version=<version>
810 Where *<storage>* is the storage you want to put the state on, and *<version>*
811 is either 'v1.2' or 'v2.0'. You can also add one via the web interface, by
812 choosing 'Add' -> 'TPM State' in the hardware section of a VM.
814 The 'v2.0' TPM spec is newer and better supported, so unless you have a specific
815 implementation that requires a 'v1.2' TPM, it should be preferred.
817 NOTE: Compared to a physical TPM, an emulated one does *not* provide any real
818 security benefits. The point of a TPM is that the data on it cannot be modified
819 easily, except via commands specified as part of the TPM spec. Since with an
820 emulated device the data storage happens on a regular volume, it can potentially
821 be edited by anyone with access to it.
824 Inter-VM shared memory
825 ~~~~~~~~~~~~~~~~~~~~~~
827 You can add an Inter-VM shared memory device (`ivshmem`), which allows one to
828 share memory between the host and a guest, or also between multiple guests.
830 To add such a device, you can use `qm`:
833 # qm set <vmid> -ivshmem size=32,name=foo
836 Where the size is in MiB. The file will be located under
837 `/dev/shm/pve-shm-$name` (the default name is the vmid).
839 NOTE: Currently the device will get deleted as soon as any VM using it got
840 shutdown or stopped. Open connections will still persist, but new connections
841 to the exact same device cannot be made anymore.
843 A use case for such a device is the Looking Glass
844 footnote:[Looking Glass: https://looking-glass.io/] project, which enables high
845 performance, low-latency display mirroring between host and guest.
851 To add an audio device run the following command:
854 qm set <vmid> -audio0 device=<device>
857 Supported audio devices are:
859 * `ich9-intel-hda`: Intel HD Audio Controller, emulates ICH9
860 * `intel-hda`: Intel HD Audio Controller, emulates ICH6
861 * `AC97`: Audio Codec '97, useful for older operating systems like Windows XP
863 There are two backends available:
868 The 'spice' backend can be used in combination with xref:qm_display[SPICE] while
869 the 'none' backend can be useful if an audio device is needed in the VM for some
870 software to work. To use the physical audio device of the host use device
871 passthrough (see xref:qm_pci_passthrough[PCI Passthrough] and
872 xref:qm_usb_passthrough[USB Passthrough]). Remote protocols like Microsoft’s RDP
873 have options to play sound.
880 A RNG (Random Number Generator) is a device providing entropy ('randomness') to
881 a system. A virtual hardware-RNG can be used to provide such entropy from the
882 host system to a guest VM. This helps to avoid entropy starvation problems in
883 the guest (a situation where not enough entropy is available and the system may
884 slow down or run into problems), especially during the guests boot process.
886 To add a VirtIO-based emulated RNG, run the following command:
889 qm set <vmid> -rng0 source=<source>[,max_bytes=X,period=Y]
892 `source` specifies where entropy is read from on the host and has to be one of
895 * `/dev/urandom`: Non-blocking kernel entropy pool (preferred)
896 * `/dev/random`: Blocking kernel pool (not recommended, can lead to entropy
897 starvation on the host system)
898 * `/dev/hwrng`: To pass through a hardware RNG attached to the host (if multiple
899 are available, the one selected in
900 `/sys/devices/virtual/misc/hw_random/rng_current` will be used)
902 A limit can be specified via the `max_bytes` and `period` parameters, they are
903 read as `max_bytes` per `period` in milliseconds. However, it does not represent
904 a linear relationship: 1024B/1000ms would mean that up to 1 KiB of data becomes
905 available on a 1 second timer, not that 1 KiB is streamed to the guest over the
906 course of one second. Reducing the `period` can thus be used to inject entropy
907 into the guest at a faster rate.
909 By default, the limit is set to 1024 bytes per 1000 ms (1 KiB/s). It is
910 recommended to always use a limiter to avoid guests using too many host
911 resources. If desired, a value of '0' for `max_bytes` can be used to disable
918 QEMU can tell the guest which devices it should boot from, and in which order.
919 This can be specified in the config via the `boot` property, for example:
922 boot: order=scsi0;net0;hostpci0
925 [thumbnail="screenshot/gui-qemu-edit-bootorder.png"]
927 This way, the guest would first attempt to boot from the disk `scsi0`, if that
928 fails, it would go on to attempt network boot from `net0`, and in case that
929 fails too, finally attempt to boot from a passed through PCIe device (seen as
930 disk in case of NVMe, otherwise tries to launch into an option ROM).
932 On the GUI you can use a drag-and-drop editor to specify the boot order, and use
933 the checkbox to enable or disable certain devices for booting altogether.
935 NOTE: If your guest uses multiple disks to boot the OS or load the bootloader,
936 all of them must be marked as 'bootable' (that is, they must have the checkbox
937 enabled or appear in the list in the config) for the guest to be able to boot.
938 This is because recent SeaBIOS and OVMF versions only initialize disks if they
939 are marked 'bootable'.
941 In any case, even devices not appearing in the list or having the checkmark
942 disabled will still be available to the guest, once it's operating system has
943 booted and initialized them. The 'bootable' flag only affects the guest BIOS and
947 [[qm_startup_and_shutdown]]
948 Automatic Start and Shutdown of Virtual Machines
949 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
951 After creating your VMs, you probably want them to start automatically
952 when the host system boots. For this you need to select the option 'Start at
953 boot' from the 'Options' Tab of your VM in the web interface, or set it with
954 the following command:
957 # qm set <vmid> -onboot 1
960 .Start and Shutdown Order
962 [thumbnail="screenshot/gui-qemu-edit-start-order.png"]
964 In some case you want to be able to fine tune the boot order of your
965 VMs, for instance if one of your VM is providing firewalling or DHCP
966 to other guest systems. For this you can use the following
969 * *Start/Shutdown order*: Defines the start order priority. For example, set it
971 you want the VM to be the first to be started. (We use the reverse startup
972 order for shutdown, so a machine with a start order of 1 would be the last to
973 be shut down). If multiple VMs have the same order defined on a host, they will
974 additionally be ordered by 'VMID' in ascending order.
975 * *Startup delay*: Defines the interval between this VM start and subsequent
976 VMs starts. For example, set it to 240 if you want to wait 240 seconds before
978 * *Shutdown timeout*: Defines the duration in seconds {pve} should wait
979 for the VM to be offline after issuing a shutdown command. By default this
980 value is set to 180, which means that {pve} will issue a shutdown request and
981 wait 180 seconds for the machine to be offline. If the machine is still online
982 after the timeout it will be stopped forcefully.
984 NOTE: VMs managed by the HA stack do not follow the 'start on boot' and
985 'boot order' options currently. Those VMs will be skipped by the startup and
986 shutdown algorithm as the HA manager itself ensures that VMs get started and
989 Please note that machines without a Start/Shutdown order parameter will always
990 start after those where the parameter is set. Further, this parameter can only
991 be enforced between virtual machines running on the same host, not
994 If you require a delay between the host boot and the booting of the first VM,
995 see the section on xref:first_guest_boot_delay[Proxmox VE Node Management].
1002 The Qemu Guest Agent is a service which runs inside the VM, providing a
1003 communication channel between the host and the guest. It is used to exchange
1004 information and allows the host to issue commands to the guest.
1006 For example, the IP addresses in the VM summary panel are fetched via the guest
1009 Or when starting a backup, the guest is told via the guest agent to sync
1010 outstanding writes via the 'fs-freeze' and 'fs-thaw' commands.
1012 For the guest agent to work properly the following steps must be taken:
1014 * install the agent in the guest and make sure it is running
1015 * enable the communication via the agent in {pve}
1020 For most Linux distributions, the guest agent is available. The package is
1021 usually named `qemu-guest-agent`.
1023 For Windows, it can be installed from the
1024 https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso[Fedora
1027 Enable Guest Agent Communication
1028 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1030 Communication from {pve} with the guest agent can be enabled in the VM's
1031 *Options* panel. A fresh start of the VM is necessary for the changes to take
1034 It is possible to enable the 'Run guest-trim' option. With this enabled,
1035 {pve} will issue a trim command to the guest after the following
1036 operations that have the potential to write out zeros to the storage:
1038 * moving a disk to another storage
1039 * live migrating a VM to another node with local storage
1041 On a thin provisioned storage, this can help to free up unused space.
1046 .VM does not shut down
1048 Make sure the guest agent is installed and running.
1050 Once the guest agent is enabled, {pve} will send power commands like
1051 'shutdown' via the guest agent. If the guest agent is not running, commands
1052 cannot get executed properly and the shutdown command will run into a timeout.
1054 [[qm_spice_enhancements]]
1058 SPICE Enhancements are optional features that can improve the remote viewer
1061 To enable them via the GUI go to the *Options* panel of the virtual machine. Run
1062 the following command to enable them via the CLI:
1065 qm set <vmid> -spice_enhancements foldersharing=1,videostreaming=all
1068 NOTE: To use these features the <<qm_display,*Display*>> of the virtual machine
1069 must be set to SPICE (qxl).
1074 Share a local folder with the guest. The `spice-webdavd` daemon needs to be
1075 installed in the guest. It makes the shared folder available through a local
1076 WebDAV server located at http://localhost:9843.
1078 For Windows guests the installer for the 'Spice WebDAV daemon' can be downloaded
1080 https://www.spice-space.org/download.html#windows-binaries[official SPICE website].
1082 Most Linux distributions have a package called `spice-webdavd` that can be
1085 To share a folder in Virt-Viewer (Remote Viewer) go to 'File -> Preferences'.
1086 Select the folder to share and then enable the checkbox.
1088 NOTE: Folder sharing currently only works in the Linux version of Virt-Viewer.
1090 CAUTION: Experimental! Currently this feature does not work reliably.
1095 Fast refreshing areas are encoded into a video stream. Two options exist:
1097 * *all*: Any fast refreshing area will be encoded into a video stream.
1098 * *filter*: Additional filters are used to decide if video streaming should be
1099 used (currently only small window surfaces are skipped).
1101 A general recommendation if video streaming should be enabled and which option
1102 to choose from cannot be given. Your mileage may vary depending on the specific
1108 .Shared folder does not show up
1110 Make sure the WebDAV service is enabled and running in the guest. On Windows it
1111 is called 'Spice webdav proxy'. In Linux the name is 'spice-webdavd' but can be
1112 different depending on the distribution.
1114 If the service is running, check the WebDAV server by opening
1115 http://localhost:9843 in a browser in the guest.
1117 It can help to restart the SPICE session.
1123 [thumbnail="screenshot/gui-qemu-migrate.png"]
1125 If you have a cluster, you can migrate your VM to another host with
1128 # qm migrate <vmid> <target>
1131 There are generally two mechanisms for this
1133 * Online Migration (aka Live Migration)
1139 If your VM is running and no locally bound resources are configured (such as
1140 passed-through devices), you can initiate a live migration with the `--online`
1141 flag in the `qm migration` command evocation. The web-interface defaults to
1142 live migration when the VM is running.
1147 Online migration first starts a new QEMU process on the target host with the
1148 'incoming' flag, which performs only basic initialization with the guest vCPUs
1149 still paused and then waits for the guest memory and device state data streams
1150 of the source Virtual Machine.
1151 All other resources, such as disks, are either shared or got already sent
1152 before runtime state migration of the VMs begins; so only the memory content
1153 and device state remain to be transferred.
1155 Once this connection is established, the source begins asynchronously sending
1156 the memory content to the target. If the guest memory on the source changes,
1157 those sections are marked dirty and another pass is made to send the guest
1159 This loop is repeated until the data difference between running source VM
1160 and incoming target VM is small enough to be sent in a few milliseconds,
1161 because then the source VM can be paused completely, without a user or program
1162 noticing the pause, so that the remaining data can be sent to the target, and
1163 then unpause the targets VM's CPU to make it the new running VM in well under a
1169 For Live Migration to work, there are some things required:
1171 * The VM has no local resources that cannot be migrated. For example,
1172 PCI or USB devices that are passed through currently block live-migration.
1173 Local Disks, on the other hand, can be migrated by sending them to the target
1175 * The hosts are located in the same {pve} cluster.
1176 * The hosts have a working (and reliable) network connection between them.
1177 * The target host must have the same, or higher versions of the
1178 {pve} packages. Although it can sometimes work the other way around, this
1179 cannot be guaranteed.
1180 * The hosts have CPUs from the same vendor with similar capabilities. Different
1181 vendor *might* work depending on the actual models and VMs CPU type
1182 configured, but it cannot be guaranteed - so please test before deploying
1183 such a setup in production.
1188 If you have local resources, you can still migrate your VMs offline as long as
1189 all disk are on storage defined on both hosts.
1190 Migration then copies the disks to the target host over the network, as with
1191 online migration. Note that any hardware pass-through configuration may need to
1192 be adapted to the device location on the target host.
1194 // TODO: mention hardware map IDs as better way to solve that, once available
1196 [[qm_copy_and_clone]]
1200 [thumbnail="screenshot/gui-qemu-full-clone.png"]
1202 VM installation is usually done using an installation media (CD-ROM)
1203 from the operating system vendor. Depending on the OS, this can be a
1204 time consuming task one might want to avoid.
1206 An easy way to deploy many VMs of the same type is to copy an existing
1207 VM. We use the term 'clone' for such copies, and distinguish between
1208 'linked' and 'full' clones.
1212 The result of such copy is an independent VM. The
1213 new VM does not share any storage resources with the original.
1216 It is possible to select a *Target Storage*, so one can use this to
1217 migrate a VM to a totally different storage. You can also change the
1218 disk image *Format* if the storage driver supports several formats.
1221 NOTE: A full clone needs to read and copy all VM image data. This is
1222 usually much slower than creating a linked clone.
1225 Some storage types allows to copy a specific *Snapshot*, which
1226 defaults to the 'current' VM data. This also means that the final copy
1227 never includes any additional snapshots from the original VM.
1232 Modern storage drivers support a way to generate fast linked
1233 clones. Such a clone is a writable copy whose initial contents are the
1234 same as the original data. Creating a linked clone is nearly
1235 instantaneous, and initially consumes no additional space.
1238 They are called 'linked' because the new image still refers to the
1239 original. Unmodified data blocks are read from the original image, but
1240 modification are written (and afterwards read) from a new
1241 location. This technique is called 'Copy-on-write'.
1244 This requires that the original volume is read-only. With {pve} one
1245 can convert any VM into a read-only <<qm_templates, Template>>). Such
1246 templates can later be used to create linked clones efficiently.
1249 NOTE: You cannot delete an original template while linked clones
1253 It is not possible to change the *Target storage* for linked clones,
1254 because this is a storage internal feature.
1257 The *Target node* option allows you to create the new VM on a
1258 different node. The only restriction is that the VM is on shared
1259 storage, and that storage is also available on the target node.
1261 To avoid resource conflicts, all network interface MAC addresses get
1262 randomized, and we generate a new 'UUID' for the VM BIOS (smbios1)
1267 Virtual Machine Templates
1268 -------------------------
1270 One can convert a VM into a Template. Such templates are read-only,
1271 and you can use them to create linked clones.
1273 NOTE: It is not possible to start templates, because this would modify
1274 the disk images. If you want to change the template, create a linked
1275 clone and modify that.
1280 {pve} supports Virtual Machine Generation ID ('vmgenid') footnote:[Official
1281 'vmgenid' Specification
1282 https://docs.microsoft.com/en-us/windows/desktop/hyperv_v2/virtual-machine-generation-identifier]
1283 for virtual machines.
1284 This can be used by the guest operating system to detect any event resulting
1285 in a time shift event, for example, restoring a backup or a snapshot rollback.
1287 When creating new VMs, a 'vmgenid' will be automatically generated and saved
1288 in its configuration file.
1290 To create and add a 'vmgenid' to an already existing VM one can pass the
1291 special value `1' to let {pve} autogenerate one or manually set the 'UUID'
1292 footnote:[Online GUID generator http://guid.one/] by using it as value, for
1296 # qm set VMID -vmgenid 1
1297 # qm set VMID -vmgenid 00000000-0000-0000-0000-000000000000
1300 NOTE: The initial addition of a 'vmgenid' device to an existing VM, may result
1301 in the same effects as a change on snapshot rollback, backup restore, etc., has
1302 as the VM can interpret this as generation change.
1304 In the rare case the 'vmgenid' mechanism is not wanted one can pass `0' for
1305 its value on VM creation, or retroactively delete the property in the
1309 # qm set VMID -delete vmgenid
1312 The most prominent use case for 'vmgenid' are newer Microsoft Windows
1313 operating systems, which use it to avoid problems in time sensitive or
1314 replicate services (such as databases or domain controller
1315 footnote:[https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/get-started/virtual-dc/virtualized-domain-controller-architecture])
1316 on snapshot rollback, backup restore or a whole VM clone operation.
1318 Importing Virtual Machines and disk images
1319 ------------------------------------------
1321 A VM export from a foreign hypervisor takes usually the form of one or more disk
1322 images, with a configuration file describing the settings of the VM (RAM,
1324 The disk images can be in the vmdk format, if the disks come from
1325 VMware or VirtualBox, or qcow2 if the disks come from a KVM hypervisor.
1326 The most popular configuration format for VM exports is the OVF standard, but in
1327 practice interoperation is limited because many settings are not implemented in
1328 the standard itself, and hypervisors export the supplementary information
1329 in non-standard extensions.
1331 Besides the problem of format, importing disk images from other hypervisors
1332 may fail if the emulated hardware changes too much from one hypervisor to
1333 another. Windows VMs are particularly concerned by this, as the OS is very
1334 picky about any changes of hardware. This problem may be solved by
1335 installing the MergeIDE.zip utility available from the Internet before exporting
1336 and choosing a hard disk type of *IDE* before booting the imported Windows VM.
1338 Finally there is the question of paravirtualized drivers, which improve the
1339 speed of the emulated system and are specific to the hypervisor.
1340 GNU/Linux and other free Unix OSes have all the necessary drivers installed by
1341 default and you can switch to the paravirtualized drivers right after importing
1342 the VM. For Windows VMs, you need to install the Windows paravirtualized
1343 drivers by yourself.
1345 GNU/Linux and other free Unix can usually be imported without hassle. Note
1346 that we cannot guarantee a successful import/export of Windows VMs in all
1347 cases due to the problems above.
1349 Step-by-step example of a Windows OVF import
1350 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1353 https://developer.microsoft.com/en-us/windows/downloads/virtual-machines/[Virtual Machines downloads]
1354 to get started with Windows development.We are going to use one of these
1355 to demonstrate the OVF import feature.
1357 Download the Virtual Machine zip
1358 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1360 After getting informed about the user agreement, choose the _Windows 10
1361 Enterprise (Evaluation - Build)_ for the VMware platform, and download the zip.
1363 Extract the disk image from the zip
1364 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1366 Using the `unzip` utility or any archiver of your choice, unpack the zip,
1367 and copy via ssh/scp the ovf and vmdk files to your {pve} host.
1369 Import the Virtual Machine
1370 ^^^^^^^^^^^^^^^^^^^^^^^^^^
1372 This will create a new virtual machine, using cores, memory and
1373 VM name as read from the OVF manifest, and import the disks to the +local-lvm+
1374 storage. You have to configure the network manually.
1377 # qm importovf 999 WinDev1709Eval.ovf local-lvm
1380 The VM is ready to be started.
1382 Adding an external disk image to a Virtual Machine
1383 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1385 You can also add an existing disk image to a VM, either coming from a
1386 foreign hypervisor, or one that you created yourself.
1388 Suppose you created a Debian/Ubuntu disk image with the 'vmdebootstrap' tool:
1390 vmdebootstrap --verbose \
1391 --size 10GiB --serial-console \
1392 --grub --no-extlinux \
1393 --package openssh-server \
1394 --package avahi-daemon \
1395 --package qemu-guest-agent \
1396 --hostname vm600 --enable-dhcp \
1397 --customize=./copy_pub_ssh.sh \
1398 --sparse --image vm600.raw
1400 You can now create a new target VM, importing the image to the storage `pvedir`
1401 and attaching it to the VM's SCSI controller:
1404 # qm create 600 --net0 virtio,bridge=vmbr0 --name vm600 --serial0 socket \
1405 --boot order=scsi0 --scsihw virtio-scsi-pci --ostype l26 \
1406 --scsi0 pvedir:0,import-from=/path/to/dir/vm600.raw
1409 The VM is ready to be started.
1413 include::qm-cloud-init.adoc[]
1417 include::qm-pci-passthrough.adoc[]
1423 You can add a hook script to VMs with the config property `hookscript`.
1426 # qm set 100 --hookscript local:snippets/hookscript.pl
1429 It will be called during various phases of the guests lifetime.
1430 For an example and documentation see the example script under
1431 `/usr/share/pve-docs/examples/guest-example-hookscript.pl`.
1437 You can suspend a VM to disk with the GUI option `Hibernate` or with
1440 # qm suspend ID --todisk
1443 That means that the current content of the memory will be saved onto disk
1444 and the VM gets stopped. On the next start, the memory content will be
1445 loaded and the VM can continue where it was left off.
1447 [[qm_vmstatestorage]]
1448 .State storage selection
1449 If no target storage for the memory is given, it will be automatically
1450 chosen, the first of:
1452 1. The storage `vmstatestorage` from the VM config.
1453 2. The first shared storage from any VM disk.
1454 3. The first non-shared storage from any VM disk.
1455 4. The storage `local` as a fallback.
1457 Managing Virtual Machines with `qm`
1458 ------------------------------------
1460 qm is the tool to manage Qemu/Kvm virtual machines on {pve}. You can
1461 create and destroy virtual machines, and control execution
1462 (start/stop/suspend/resume). Besides that, you can use qm to set
1463 parameters in the associated config file. It is also possible to
1464 create and delete virtual disks.
1469 Using an iso file uploaded on the 'local' storage, create a VM
1470 with a 4 GB IDE disk on the 'local-lvm' storage
1473 # qm create 300 -ide0 local-lvm:4 -net0 e1000 -cdrom local:iso/proxmox-mailgateway_2.1.iso
1482 Send a shutdown request, then wait until the VM is stopped.
1485 # qm shutdown 300 && qm wait 300
1488 Same as above, but only wait for 40 seconds.
1491 # qm shutdown 300 && qm wait 300 -timeout 40
1494 Destroying a VM always removes it from Access Control Lists and it always
1495 removes the firewall configuration of the VM. You have to activate
1496 '--purge', if you want to additionally remove the VM from replication jobs,
1497 backup jobs and HA resource configurations.
1500 # qm destroy 300 --purge
1503 Move a disk image to a different storage.
1506 # qm move-disk 300 scsi0 other-storage
1509 Reassign a disk image to a different VM. This will remove the disk `scsi1` from
1510 the source VM and attaches it as `scsi3` to the target VM. In the background
1511 the disk image is being renamed so that the name matches the new owner.
1514 # qm move-disk 300 scsi1 --target-vmid 400 --target-disk scsi3
1518 [[qm_configuration]]
1522 VM configuration files are stored inside the Proxmox cluster file
1523 system, and can be accessed at `/etc/pve/qemu-server/<VMID>.conf`.
1524 Like other files stored inside `/etc/pve/`, they get automatically
1525 replicated to all other cluster nodes.
1527 NOTE: VMIDs < 100 are reserved for internal purposes, and VMIDs need to be
1528 unique cluster wide.
1530 .Example VM Configuration
1532 boot: order=virtio0;net0
1538 net0: e1000=EE:D2:28:5F:B6:3E,bridge=vmbr0
1539 virtio0: local:vm-100-disk-1,size=32G
1542 Those configuration files are simple text files, and you can edit them
1543 using a normal text editor (`vi`, `nano`, ...). This is sometimes
1544 useful to do small corrections, but keep in mind that you need to
1545 restart the VM to apply such changes.
1547 For that reason, it is usually better to use the `qm` command to
1548 generate and modify those files, or do the whole thing using the GUI.
1549 Our toolkit is smart enough to instantaneously apply most changes to
1550 running VM. This feature is called "hot plug", and there is no
1551 need to restart the VM in that case.
1557 VM configuration files use a simple colon separated key/value
1558 format. Each line has the following format:
1565 Blank lines in those files are ignored, and lines starting with a `#`
1566 character are treated as comments and are also ignored.
1573 When you create a snapshot, `qm` stores the configuration at snapshot
1574 time into a separate snapshot section within the same configuration
1575 file. For example, after creating a snapshot called ``testsnapshot'',
1576 your configuration file will look like this:
1578 .VM configuration with snapshot
1588 snaptime: 1457170803
1592 There are a few snapshot related properties like `parent` and
1593 `snaptime`. The `parent` property is used to store the parent/child
1594 relationship between snapshots. `snaptime` is the snapshot creation
1595 time stamp (Unix epoch).
1597 You can optionally save the memory of a running VM with the option `vmstate`.
1598 For details about how the target storage gets chosen for the VM state, see
1599 xref:qm_vmstatestorage[State storage selection] in the chapter
1600 xref:qm_hibernate[Hibernation].
1606 include::qm.conf.5-opts.adoc[]
1612 Online migrations, snapshots and backups (`vzdump`) set a lock to prevent
1613 incompatible concurrent actions on the affected VMs. Sometimes you need to
1614 remove such a lock manually (for example after a power failure).
1620 CAUTION: Only do that if you are sure the action which set the lock is
1629 * link:/wiki/Cloud-Init_Support[Cloud-Init Support]
1639 `/etc/pve/qemu-server/<VMID>.conf`::
1641 Configuration file for the VM '<VMID>'.
1644 include::pve-copyright.adoc[]