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80c0adcb 1[[chapter_virtual_machines]]
f69cfd23 2ifdef::manvolnum[]
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3qm(1)
4=====
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5:pve-toplevel:
6
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7NAME
8----
9
10qm - Qemu/KVM Virtual Machine Manager
11
12
49a5e11c 13SYNOPSIS
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14--------
15
16include::qm.1-synopsis.adoc[]
17
18DESCRIPTION
19-----------
20endif::manvolnum[]
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21ifndef::manvolnum[]
22Qemu/KVM Virtual Machines
23=========================
5f09af76 24:pve-toplevel:
194d2f29 25endif::manvolnum[]
5f09af76 26
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27// deprecates
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
31
5eba0743 32Qemu (short form for Quick Emulator) is an open source hypervisor that emulates a
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33physical computer. From the perspective of the host system where Qemu is
34running, Qemu is a user program which has access to a number of local resources
35like partitions, files, network cards which are then passed to an
189d3661 36emulated computer which sees them as if they were real devices.
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37
38A guest operating system running in the emulated computer accesses these
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39devices, and runs as if it were running on real hardware. For instance, you can pass
40an ISO image as a parameter to Qemu, and the OS running in the emulated computer
41will see a real CD-ROM inserted into a CD drive.
c4cba5d7 42
6fb50457 43Qemu can emulate a great variety of hardware from ARM to Sparc, but {pve} is
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44only concerned with 32 and 64 bits PC clone emulation, since it represents the
45overwhelming majority of server hardware. The emulation of PC clones is also one
46of the fastest due to the availability of processor extensions which greatly
47speed up Qemu when the emulated architecture is the same as the host
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48architecture.
49
50NOTE: You may sometimes encounter the term _KVM_ (Kernel-based Virtual Machine).
51It means that Qemu is running with the support of the virtualization processor
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52extensions, 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
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54module.
55
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56Qemu inside {pve} runs as a root process, since this is required to access block
57and PCI devices.
58
5eba0743 59
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60Emulated devices and paravirtualized devices
61--------------------------------------------
62
189d3661 63The PC hardware emulated by Qemu includes a mainboard, network controllers,
3a433e9b 64SCSI, IDE and SATA controllers, serial ports (the complete list can be seen in
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65the `kvm(1)` man page) all of them emulated in software. All these devices
66are the exact software equivalent of existing hardware devices, and if the OS
67running in the guest has the proper drivers it will use the devices as if it
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68were running on real hardware. This allows Qemu to runs _unmodified_ operating
69systems.
70
71This however has a performance cost, as running in software what was meant to
72run in hardware involves a lot of extra work for the host CPU. To mitigate this,
73Qemu can present to the guest operating system _paravirtualized devices_, where
74the guest OS recognizes it is running inside Qemu and cooperates with the
75hypervisor.
76
470d4313 77Qemu relies on the virtio virtualization standard, and is thus able to present
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78paravirtualized virtio devices, which includes a paravirtualized generic disk
79controller, a paravirtualized network card, a paravirtualized serial port,
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80a paravirtualized SCSI controller, etc ...
81
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82It is highly recommended to use the virtio devices whenever you can, as they
83provide a big performance improvement. Using the virtio generic disk controller
84versus an emulated IDE controller will double the sequential write throughput,
85as measured with `bonnie++(8)`. Using the virtio network interface can deliver
c4cba5d7 86up to three times the throughput of an emulated Intel E1000 network card, as
189d3661 87measured with `iperf(1)`. footnote:[See this benchmark on the KVM wiki
a55d30db 88https://www.linux-kvm.org/page/Using_VirtIO_NIC]
c4cba5d7 89
5eba0743 90
80c0adcb 91[[qm_virtual_machines_settings]]
5274ad28 92Virtual Machines Settings
c4cba5d7 93-------------------------
80c0adcb 94
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95Generally 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
97could incur a performance slowdown, or putting your data at risk.
98
5eba0743 99
80c0adcb 100[[qm_general_settings]]
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101General Settings
102~~~~~~~~~~~~~~~~
80c0adcb 103
1ff5e4e8 104[thumbnail="screenshot/gui-create-vm-general.png"]
b16d767f 105
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106General settings of a VM include
107
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
112
5eba0743 113
80c0adcb 114[[qm_os_settings]]
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115OS Settings
116~~~~~~~~~~~
80c0adcb 117
1ff5e4e8 118[thumbnail="screenshot/gui-create-vm-os.png"]
200114a7 119
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120When creating a virtual machine (VM), setting the proper Operating System(OS)
121allows {pve} to optimize some low level parameters. For instance Windows OS
122expect the BIOS clock to use the local time, while Unix based OS expect the
123BIOS clock to have the UTC time.
124
125[[qm_system_settings]]
126System Settings
127~~~~~~~~~~~~~~~
128
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129On VM creation you can change some basic system components of the new VM. You
130can specify which xref:qm_display[display type] you want to use.
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131[thumbnail="screenshot/gui-create-vm-system.png"]
132Additionally, the xref:qm_hard_disk[SCSI controller] can be changed.
133If you plan to install the QEMU Guest Agent, or if your selected ISO image
134already ships and installs it automatically, you may want to tick the 'Qemu
135Agent' box, which lets {pve} know that it can use its features to show some
136more information, and complete some actions (for example, shutdown or
137snapshots) more intelligently.
138
139{pve} allows to boot VMs with different firmware and machine types, namely
140xref:qm_bios_and_uefi[SeaBIOS and OVMF]. In most cases you want to switch from
3a433e9b 141the default SeaBIOS to OVMF only if you plan to use
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142xref:qm_pci_passthrough[PCIe pass through]. A VMs 'Machine Type' defines the
143hardware layout of the VM's virtual motherboard. You can choose between the
144default https://en.wikipedia.org/wiki/Intel_440FX[Intel 440FX] or the
145https://ark.intel.com/content/www/us/en/ark/products/31918/intel-82q35-graphics-and-memory-controller.html[Q35]
146chipset, which also provides a virtual PCIe bus, and thus may be desired if
5f318cc0 147one wants to pass through PCIe hardware.
5eba0743 148
80c0adcb 149[[qm_hard_disk]]
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150Hard Disk
151~~~~~~~~~
80c0adcb 152
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153[[qm_hard_disk_bus]]
154Bus/Controller
155^^^^^^^^^^^^^^
2ec49380 156Qemu can emulate a number of storage controllers:
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157
158* the *IDE* controller, has a design which goes back to the 1984 PC/AT disk
44f38275 159controller. Even if this controller has been superseded by recent designs,
6fb50457 160each and every OS you can think of has support for it, making it a great choice
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161if you want to run an OS released before 2003. You can connect up to 4 devices
162on this controller.
163
164* the *SATA* (Serial ATA) controller, dating from 2003, has a more modern
165design, allowing higher throughput and a greater number of devices to be
166connected. You can connect up to 6 devices on this controller.
167
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168* the *SCSI* controller, designed in 1985, is commonly found on server grade
169hardware, and can connect up to 14 storage devices. {pve} emulates by default a
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170LSI 53C895A controller.
171+
81868c7e 172A SCSI controller of type _VirtIO SCSI_ is the recommended setting if you aim for
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173performance and is automatically selected for newly created Linux VMs since
174{pve} 4.3. Linux distributions have support for this controller since 2012, and
c4cba5d7 175FreeBSD since 2014. For Windows OSes, you need to provide an extra iso
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176containing the drivers during the installation.
177// https://pve.proxmox.com/wiki/Paravirtualized_Block_Drivers_for_Windows#During_windows_installation.
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178If 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.
180When selecting _VirtIO SCSI single_ Qemu will create a new controller for
181each disk, instead of adding all disks to the same controller.
b0b6802b 182
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183* The *VirtIO Block* controller, often just called VirtIO or virtio-blk,
184is an older type of paravirtualized controller. It has been superseded by the
185VirtIO SCSI Controller, in terms of features.
c4cba5d7 186
1ff5e4e8 187[thumbnail="screenshot/gui-create-vm-hard-disk.png"]
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188
189[[qm_hard_disk_formats]]
190Image Format
191^^^^^^^^^^^^
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192On each controller you attach a number of emulated hard disks, which are backed
193by a file or a block device residing in the configured storage. The choice of
194a storage type will determine the format of the hard disk image. Storages which
195present block devices (LVM, ZFS, Ceph) will require the *raw disk image format*,
de14ebff 196whereas files based storages (Ext4, NFS, CIFS, GlusterFS) will let you to choose
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197either the *raw disk image format* or the *QEMU image format*.
198
199 * the *QEMU image format* is a copy on write format which allows snapshots, and
200 thin provisioning of the disk image.
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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
4371b2fe 203 format does not support thin provisioning or snapshots by itself, requiring
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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
43530f6f 206 https://events.static.linuxfound.org/sites/events/files/slides/CloudOpen2013_Khoa_Huynh_v3.pdf]
189d3661 207 * the *VMware image format* only makes sense if you intend to import/export the
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208 disk image to other hypervisors.
209
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210[[qm_hard_disk_cache]]
211Cache Mode
212^^^^^^^^^^
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213Setting the *Cache* mode of the hard drive will impact how the host system will
214notify the guest systems of block write completions. The *No cache* default
215means that the guest system will be notified that a write is complete when each
216block reaches the physical storage write queue, ignoring the host page cache.
217This provides a good balance between safety and speed.
218
219If you want the {pve} backup manager to skip a disk when doing a backup of a VM,
220you can set the *No backup* option on that disk.
221
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222If 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.
6fb50457 224As of {pve} 5.0, replication requires the disk images to be on a storage of type
3205ac49 225`zfspool`, so adding a disk image to other storages when the VM has replication
6fb50457 226configured requires to skip replication for this disk image.
3205ac49 227
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228[[qm_hard_disk_discard]]
229Trim/Discard
230^^^^^^^^^^^^
c4cba5d7 231If your storage supports _thin provisioning_ (see the storage chapter in the
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232{pve} guide), you can activate the *Discard* option on a drive. With *Discard*
233set and a _TRIM_-enabled guest OS footnote:[TRIM, UNMAP, and discard
234https://en.wikipedia.org/wiki/Trim_%28computing%29], when the VM's filesystem
235marks blocks as unused after deleting files, the controller will relay this
236information to the storage, which will then shrink the disk image accordingly.
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237For the guest to be able to issue _TRIM_ commands, you must enable the *Discard*
238option 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
240only supported on guests using Linux Kernel 5.0 or higher.
c4cba5d7 241
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242If you would like a drive to be presented to the guest as a solid-state drive
243rather than a rotational hard disk, you can set the *SSD emulation* option on
244that drive. There is no requirement that the underlying storage actually be
245backed by SSDs; this feature can be used with physical media of any type.
53cbac40 246Note that *SSD emulation* is not supported on *VirtIO Block* drives.
25203dc1 247
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248
249[[qm_hard_disk_iothread]]
250IO Thread
251^^^^^^^^^
59552707 252The option *IO Thread* can only be used when using a disk with the
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253*VirtIO* controller, or with the *SCSI* controller, when the emulated controller
254 type is *VirtIO SCSI single*.
255With this enabled, Qemu creates one I/O thread per storage controller,
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256rather than a single thread for all I/O. This can increase performance when
257multiple disks are used and each disk has its own storage controller.
c564fc52 258
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259
260[[qm_cpu]]
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261CPU
262~~~
80c0adcb 263
1ff5e4e8 264[thumbnail="screenshot/gui-create-vm-cpu.png"]
397c74c3 265
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266A *CPU socket* is a physical slot on a PC motherboard where you can plug a CPU.
267This CPU can then contain one or many *cores*, which are independent
268processing units. Whether you have a single CPU socket with 4 cores, or two CPU
269sockets with two cores is mostly irrelevant from a performance point of view.
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270However some software licenses depend on the number of sockets a machine has,
271in that case it makes sense to set the number of sockets to what the license
272allows you.
f4bfd701 273
3a433e9b 274Increasing the number of virtual CPUs (cores and sockets) will usually provide a
34e541c5 275performance improvement though that is heavily dependent on the use of the VM.
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276Multi-threaded applications will of course benefit from a large number of
277virtual CPUs, as for each virtual cpu you add, Qemu will create a new thread of
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278execution on the host system. If you're not sure about the workload of your VM,
279it is usually a safe bet to set the number of *Total cores* to 2.
280
fb29acdd 281NOTE: It is perfectly safe if the _overall_ number of cores of all your VMs
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282is greater than the number of cores on the server (e.g., 4 VMs with each 4
283cores on a machine with only 8 cores). In that case the host system will
284balance the Qemu execution threads between your server cores, just like if you
3a433e9b 285were running a standard multi-threaded application. However, {pve} will prevent
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286you from starting VMs with more virtual CPU cores than physically available, as
287this will only bring the performance down due to the cost of context switches.
34e541c5 288
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289[[qm_cpu_resource_limits]]
290Resource Limits
291^^^^^^^^^^^^^^^
292
4371b2fe 293In addition to the number of virtual cores, you can configure how much resources
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294a VM can get in relation to the host CPU time and also in relation to other
295VMs.
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296With the *cpulimit* (``Host CPU Time'') option you can limit how much CPU time
297the whole VM can use on the host. It is a floating point value representing CPU
af54f54d 298time in percent, so `1.0` is equal to `100%`, `2.5` to `250%` and so on. If a
4371b2fe 299single process would fully use one single core it would have `100%` CPU Time
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300usage. If a VM with four cores utilizes all its cores fully it would
301theoretically use `400%`. In reality the usage may be even a bit higher as Qemu
302can have additional threads for VM peripherals besides the vCPU core ones.
303This setting can be useful if a VM should have multiple vCPUs, as it runs a few
304processes in parallel, but the VM as a whole should not be able to run all
305vCPUs at 100% at the same time. Using a specific example: lets say we have a VM
306which would profit from having 8 vCPUs, but at no time all of those 8 cores
307should run at full load - as this would make the server so overloaded that
308other VMs and CTs would get to less CPU. So, we set the *cpulimit* limit to
309`4.0` (=400%). If all cores do the same heavy work they would all get 50% of a
310real host cores CPU time. But, if only 4 would do work they could still get
311almost 100% of a real core each.
312
313NOTE: VMs can, depending on their configuration, use additional threads e.g.,
314for networking or IO operations but also live migration. Thus a VM can show up
315to use more CPU time than just its virtual CPUs could use. To ensure that a VM
316never uses more CPU time than virtual CPUs assigned set the *cpulimit* setting
317to the same value as the total core count.
318
319The second CPU resource limiting setting, *cpuunits* (nowadays often called CPU
320shares or CPU weight), controls how much CPU time a VM gets in regards to other
321VMs running. It is a relative weight which defaults to `1024`, if you increase
322this for a VM it will be prioritized by the scheduler in comparison to other
323VMs with lower weight. E.g., if VM 100 has set the default 1024 and VM 200 was
324changed to `2048`, the latter VM 200 would receive twice the CPU bandwidth than
325the first VM 100.
326
327For more information see `man systemd.resource-control`, here `CPUQuota`
328corresponds to `cpulimit` and `CPUShares` corresponds to our `cpuunits`
329setting, visit its Notes section for references and implementation details.
330
331CPU Type
332^^^^^^^^
333
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334Qemu can emulate a number different of *CPU types* from 486 to the latest Xeon
335processors. Each new processor generation adds new features, like hardware
336assisted 3d rendering, random number generation, memory protection, etc ...
337Usually you should select for your VM a processor type which closely matches the
338CPU of the host system, as it means that the host CPU features (also called _CPU
339flags_ ) will be available in your VMs. If you want an exact match, you can set
340the CPU type to *host* in which case the VM will have exactly the same CPU flags
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341as your host system.
342
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343This has a downside though. If you want to do a live migration of VMs between
344different hosts, your VM might end up on a new system with a different CPU type.
345If the CPU flags passed to the guest are missing, the qemu process will stop. To
346remedy this Qemu has also its own CPU type *kvm64*, that {pve} uses by defaults.
347kvm64 is a Pentium 4 look a like CPU type, which has a reduced CPU flags set,
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348but is guaranteed to work everywhere.
349
350In short, if you care about live migration and moving VMs between nodes, leave
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351the kvm64 default. If you don’t care about live migration or have a homogeneous
352cluster where all nodes have the same CPU, set the CPU type to host, as in
353theory this will give your guests maximum performance.
354
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355Custom CPU Types
356^^^^^^^^^^^^^^^^
357
358You can specify custom CPU types with a configurable set of features. These are
359maintained in the configuration file `/etc/pve/virtual-guest/cpu-models.conf` by
360an administrator. See `man cpu-models.conf` for format details.
361
362Specified custom types can be selected by any user with the `Sys.Audit`
363privilege on `/nodes`. When configuring a custom CPU type for a VM via the CLI
364or API, the name needs to be prefixed with 'custom-'.
365
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366Meltdown / Spectre related CPU flags
367^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
368
2975cb7a 369There are several CPU flags related to the Meltdown and Spectre vulnerabilities
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370footnote:[Meltdown Attack https://meltdownattack.com/] which need to be set
371manually unless the selected CPU type of your VM already enables them by default.
372
2975cb7a 373There are two requirements that need to be fulfilled in order to use these
72ae8aa2 374CPU flags:
5dba2677 375
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376* The host CPU(s) must support the feature and propagate it to the guest's virtual CPU(s)
377* The guest operating system must be updated to a version which mitigates the
378 attacks and is able to utilize the CPU feature
379
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380Otherwise you need to set the desired CPU flag of the virtual CPU, either by
381editing the CPU options in the WebUI, or by setting the 'flags' property of the
382'cpu' option in the VM configuration file.
383
384For Spectre v1,v2,v4 fixes, your CPU or system vendor also needs to provide a
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385so-called ``microcode update'' footnote:[You can use `intel-microcode' /
386`amd-microcode' from Debian non-free if your vendor does not provide such an
387update. Note that not all affected CPUs can be updated to support spec-ctrl.]
388for your CPU.
5dba2677 389
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390
391To check if the {pve} host is vulnerable, execute the following command as root:
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392
393----
2975cb7a 394for f in /sys/devices/system/cpu/vulnerabilities/*; do echo "${f##*/} -" $(cat "$f"); done
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395----
396
144d5ede 397A community script is also available to detect is the host is still vulnerable.
2975cb7a 398footnote:[spectre-meltdown-checker https://meltdown.ovh/]
72ae8aa2 399
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400Intel processors
401^^^^^^^^^^^^^^^^
72ae8aa2 402
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403* 'pcid'
404+
144d5ede 405This reduces the performance impact of the Meltdown (CVE-2017-5754) mitigation
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406called 'Kernel Page-Table Isolation (KPTI)', which effectively hides
407the Kernel memory from the user space. Without PCID, KPTI is quite an expensive
408mechanism footnote:[PCID is now a critical performance/security feature on x86
409https://groups.google.com/forum/m/#!topic/mechanical-sympathy/L9mHTbeQLNU].
410+
411To check if the {pve} host supports PCID, execute the following command as root:
412+
72ae8aa2 413----
2975cb7a 414# grep ' pcid ' /proc/cpuinfo
72ae8aa2 415----
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416+
417If this does not return empty your host's CPU has support for 'pcid'.
72ae8aa2 418
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419* 'spec-ctrl'
420+
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421Required to enable the Spectre v1 (CVE-2017-5753) and Spectre v2 (CVE-2017-5715) fix,
422in cases where retpolines are not sufficient.
423Included by default in Intel CPU models with -IBRS suffix.
424Must be explicitly turned on for Intel CPU models without -IBRS suffix.
425Requires an updated host CPU microcode (intel-microcode >= 20180425).
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426+
427* 'ssbd'
428+
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429Required to enable the Spectre V4 (CVE-2018-3639) fix. Not included by default in any Intel CPU model.
430Must be explicitly turned on for all Intel CPU models.
431Requires an updated host CPU microcode(intel-microcode >= 20180703).
72ae8aa2 432
72ae8aa2 433
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434AMD processors
435^^^^^^^^^^^^^^
436
437* 'ibpb'
438+
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439Required to enable the Spectre v1 (CVE-2017-5753) and Spectre v2 (CVE-2017-5715) fix,
440in cases where retpolines are not sufficient.
441Included by default in AMD CPU models with -IBPB suffix.
442Must be explicitly turned on for AMD CPU models without -IBPB suffix.
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443Requires the host CPU microcode to support this feature before it can be used for guest CPUs.
444
445
446
447* 'virt-ssbd'
448+
449Required to enable the Spectre v4 (CVE-2018-3639) fix.
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450Not included by default in any AMD CPU model.
451Must be explicitly turned on for all AMD CPU models.
452This should be provided to guests, even if amd-ssbd is also provided, for maximum guest compatibility.
453Note that this must be explicitly enabled when when using the "host" cpu model,
454because this is a virtual feature which does not exist in the physical CPUs.
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455
456
457* 'amd-ssbd'
458+
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459Required to enable the Spectre v4 (CVE-2018-3639) fix.
460Not included by default in any AMD CPU model. Must be explicitly turned on for all AMD CPU models.
461This provides higher performance than virt-ssbd, therefore a host supporting this should always expose this to guests if possible.
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462virt-ssbd should none the less also be exposed for maximum guest compatibility as some kernels only know about virt-ssbd.
463
464
465* 'amd-no-ssb'
466+
467Recommended to indicate the host is not vulnerable to Spectre V4 (CVE-2018-3639).
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468Not included by default in any AMD CPU model.
469Future hardware generations of CPU will not be vulnerable to CVE-2018-3639,
470and thus the guest should be told not to enable its mitigations, by exposing amd-no-ssb.
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471This is mutually exclusive with virt-ssbd and amd-ssbd.
472
5dba2677 473
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474NUMA
475^^^^
476You can also optionally emulate a *NUMA*
477footnote:[https://en.wikipedia.org/wiki/Non-uniform_memory_access] architecture
478in your VMs. The basics of the NUMA architecture mean that instead of having a
479global memory pool available to all your cores, the memory is spread into local
480banks close to each socket.
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481This can bring speed improvements as the memory bus is not a bottleneck
482anymore. If your system has a NUMA architecture footnote:[if the command
483`numactl --hardware | grep available` returns more than one node, then your host
484system has a NUMA architecture] we recommend to activate the option, as this
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485will allow proper distribution of the VM resources on the host system.
486This option is also required to hot-plug cores or RAM in a VM.
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487
488If the NUMA option is used, it is recommended to set the number of sockets to
4ccb911c 489the number of nodes of the host system.
34e541c5 490
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491vCPU hot-plug
492^^^^^^^^^^^^^
493
494Modern operating systems introduced the capability to hot-plug and, to a
3a433e9b 495certain extent, hot-unplug CPUs in a running system. Virtualization allows us
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496to avoid a lot of the (physical) problems real hardware can cause in such
497scenarios.
498Still, this is a rather new and complicated feature, so its use should be
499restricted to cases where its absolutely needed. Most of the functionality can
500be replicated with other, well tested and less complicated, features, see
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501xref:qm_cpu_resource_limits[Resource Limits].
502
503In {pve} the maximal number of plugged CPUs is always `cores * sockets`.
504To start a VM with less than this total core count of CPUs you may use the
4371b2fe 505*vpus* setting, it denotes how many vCPUs should be plugged in at VM start.
af54f54d 506
4371b2fe 507Currently only this feature is only supported on Linux, a kernel newer than 3.10
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508is needed, a kernel newer than 4.7 is recommended.
509
510You can use a udev rule as follow to automatically set new CPUs as online in
511the guest:
512
513----
514SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1"
515----
516
517Save this under /etc/udev/rules.d/ as a file ending in `.rules`.
518
519Note: CPU hot-remove is machine dependent and requires guest cooperation.
520The deletion command does not guarantee CPU removal to actually happen,
521typically it's a request forwarded to guest using target dependent mechanism,
522e.g., ACPI on x86/amd64.
523
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524
525[[qm_memory]]
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526Memory
527~~~~~~
80c0adcb 528
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529For each VM you have the option to set a fixed size memory or asking
530{pve} to dynamically allocate memory based on the current RAM usage of the
59552707 531host.
34e541c5 532
96124d0f 533.Fixed Memory Allocation
1ff5e4e8 534[thumbnail="screenshot/gui-create-vm-memory.png"]
96124d0f 535
9ea21953 536When setting memory and minimum memory to the same amount
9fb002e6 537{pve} will simply allocate what you specify to your VM.
34e541c5 538
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539Even when using a fixed memory size, the ballooning device gets added to the
540VM, because it delivers useful information such as how much memory the guest
541really uses.
542In general, you should leave *ballooning* enabled, but if you want to disable
e60ce90c 543it (e.g. for debugging purposes), simply uncheck
9fb002e6 544*Ballooning Device* or set
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545
546 balloon: 0
547
548in the configuration.
549
96124d0f 550.Automatic Memory Allocation
96124d0f 551
34e541c5 552// see autoballoon() in pvestatd.pm
58e04593 553When setting the minimum memory lower than memory, {pve} will make sure that the
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554minimum amount you specified is always available to the VM, and if RAM usage on
555the host is below 80%, will dynamically add memory to the guest up to the
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556maximum memory specified.
557
a35aad4a 558When the host is running low on RAM, the VM will then release some memory
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559back to the host, swapping running processes if needed and starting the oom
560killer in last resort. The passing around of memory between host and guest is
561done via a special `balloon` kernel driver running inside the guest, which will
562grab or release memory pages from the host.
563footnote:[A good explanation of the inner workings of the balloon driver can be found here https://rwmj.wordpress.com/2010/07/17/virtio-balloon/]
564
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565When 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
470d4313 567that each VM should take. Suppose for instance you have four VMs, three of them
a35aad4a 568running an HTTP server and the last one is a database server. To cache more
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569database blocks in the database server RAM, you would like to prioritize the
570database VM when spare RAM is available. For this you assign a Shares property
571of 3000 to the database VM, leaving the other VMs to the Shares default setting
470d4313 572of 1000. The host server has 32GB of RAM, and is currently using 16GB, leaving 32
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573* 80/100 - 16 = 9GB RAM to be allocated to the VMs. The database VM will get 9 *
5743000 / (3000 + 1000 + 1000 + 1000) = 4.5 GB extra RAM and each HTTP server will
a35aad4a 575get 1.5 GB.
c9f6e1a4 576
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577All Linux distributions released after 2010 have the balloon kernel driver
578included. For Windows OSes, the balloon driver needs to be added manually and can
579incur a slowdown of the guest, so we don't recommend using it on critical
59552707 580systems.
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581// see https://forum.proxmox.com/threads/solved-hyper-threading-vs-no-hyper-threading-fixed-vs-variable-memory.20265/
582
470d4313 583When allocating RAM to your VMs, a good rule of thumb is always to leave 1GB
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584of RAM available to the host.
585
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586
587[[qm_network_device]]
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588Network Device
589~~~~~~~~~~~~~~
80c0adcb 590
1ff5e4e8 591[thumbnail="screenshot/gui-create-vm-network.png"]
c24ddb0a 592
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593Each VM can have many _Network interface controllers_ (NIC), of four different
594types:
595
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
598performance. Like all VirtIO devices, the guest OS should have the proper driver
599installed.
600 * the *Realtek 8139* emulates an older 100 MB/s network card, and should
59552707 601only be used when emulating older operating systems ( released before 2002 )
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602 * the *vmxnet3* is another paravirtualized device, which should only be used
603when importing a VM from another hypervisor.
604
605{pve} will generate for each NIC a random *MAC address*, so that your VM is
606addressable on Ethernet networks.
607
470d4313 608The NIC you added to the VM can follow one of two different models:
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609
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
612tap device is added to a bridge, by default vmbr0 in {pve}. In this mode, VMs
613have 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
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615the Qemu user networking stack, where a built-in router and DHCP server can
616provide network access. This built-in DHCP will serve addresses in the private
af9c6de1 61710.0.2.0/24 range. The NAT mode is much slower than the bridged mode, and
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618should only be used for testing. This mode is only available via CLI or the API,
619but not via the WebUI.
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620
621You can also skip adding a network device when creating a VM by selecting *No
622network device*.
623
624.Multiqueue
1ff7835b 625If you are using the VirtIO driver, you can optionally activate the
af9c6de1 626*Multiqueue* option. This option allows the guest OS to process networking
1ff7835b 627packets using multiple virtual CPUs, providing an increase in the total number
470d4313 628of packets transferred.
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629
630//http://blog.vmsplice.net/2011/09/qemu-internals-vhost-architecture.html
631When using the VirtIO driver with {pve}, each NIC network queue is passed to the
a35aad4a 632host kernel, where the queue will be processed by a kernel thread spawned by the
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633vhost driver. With this option activated, it is possible to pass _multiple_
634network queues to the host kernel for each NIC.
635
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
af9c6de1 637When using Multiqueue, it is recommended to set it to a value equal
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638to the number of Total Cores of your guest. You also need to set in
639the VM the number of multi-purpose channels on each VirtIO NIC with the ethtool
59552707 640command:
1ff7835b 641
7a0d4784 642`ethtool -L ens1 combined X`
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643
644where X is the number of the number of vcpus of the VM.
645
af9c6de1 646You should note that setting the Multiqueue parameter to a value greater
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647than one will increase the CPU load on the host and guest systems as the
648traffic increases. We recommend to set this option only when the VM has to
649process a great number of incoming connections, such as when the VM is running
650as a router, reverse proxy or a busy HTTP server doing long polling.
651
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652[[qm_display]]
653Display
654~~~~~~~
655
656QEMU can virtualize a few types of VGA hardware. Some examples are:
657
658* *std*, the default, emulates a card with Bochs VBE extensions.
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659* *cirrus*, this was once the default, it emulates a very old hardware module
660with all its problems. This display type should only be used if really
661necessary footnote:[https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/
662qemu: using cirrus considered harmful], e.g., if using Windows XP or earlier
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663* *vmware*, is a VMWare SVGA-II compatible adapter.
664* *qxl*, is the QXL paravirtualized graphics card. Selecting this also
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665enables https://www.spice-space.org/[SPICE] (a remote viewer protocol) for the
666VM.
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667
668You can edit the amount of memory given to the virtual GPU, by setting
1368dc02 669the 'memory' option. This can enable higher resolutions inside the VM,
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670especially with SPICE/QXL.
671
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672As the memory is reserved by display device, selecting Multi-Monitor mode
673for SPICE (e.g., `qxl2` for dual monitors) has some implications:
6cb67d7f 674
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675* Windows needs a device for each monitor, so if your 'ostype' is some
676version of Windows, {pve} gives the VM an extra device per monitor.
6cb67d7f 677Each device gets the specified amount of memory.
1368dc02 678
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679* Linux VMs, can always enable more virtual monitors, but selecting
680a Multi-Monitor mode multiplies the memory given to the device with
681the number of monitors.
682
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683Selecting `serialX` as display 'type' disables the VGA output, and redirects
684the Web Console to the selected serial port. A configured display 'memory'
685setting will be ignored in that case.
80c0adcb 686
dbb44ef0 687[[qm_usb_passthrough]]
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688USB Passthrough
689~~~~~~~~~~~~~~~
80c0adcb 690
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691There are two different types of USB passthrough devices:
692
470d4313 693* Host USB passthrough
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694* SPICE USB passthrough
695
696Host USB passthrough works by giving a VM a USB device of the host.
697This can either be done via the vendor- and product-id, or
698via the host bus and port.
699
700The vendor/product-id looks like this: *0123:abcd*,
701where *0123* is the id of the vendor, and *abcd* is the id
702of the product, meaning two pieces of the same usb device
703have the same id.
704
705The bus/port looks like this: *1-2.3.4*, where *1* is the bus
706and *2.3.4* is the port path. This represents the physical
707ports of your host (depending of the internal order of the
708usb controllers).
709
710If a device is present in a VM configuration when the VM starts up,
711but the device is not present in the host, the VM can boot without problems.
470d4313 712As soon as the device/port is available in the host, it gets passed through.
685cc8e0 713
e60ce90c 714WARNING: Using this kind of USB passthrough means that you cannot move
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715a VM online to another host, since the hardware is only available
716on the host the VM is currently residing.
717
718The second type of passthrough is SPICE USB passthrough. This is useful
719if you use a SPICE client which supports it. If you add a SPICE USB port
720to your VM, you can passthrough a USB device from where your SPICE client is,
721directly to the VM (for example an input device or hardware dongle).
722
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723
724[[qm_bios_and_uefi]]
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725BIOS and UEFI
726~~~~~~~~~~~~~
727
728In order to properly emulate a computer, QEMU needs to use a firmware.
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729Which, on common PCs often known as BIOS or (U)EFI, is executed as one of the
730first steps when booting a VM. It is responsible for doing basic hardware
731initialization and for providing an interface to the firmware and hardware for
732the operating system. By default QEMU uses *SeaBIOS* for this, which is an
733open-source, x86 BIOS implementation. SeaBIOS is a good choice for most
734standard setups.
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735
736There are, however, some scenarios in which a BIOS is not a good firmware
737to boot from, e.g. if you want to do VGA passthrough. footnote:[Alex Williamson has a very good blog entry about this.
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738https://vfio.blogspot.co.at/2014/08/primary-graphics-assignment-without-vga.html]
739In such cases, you should rather use *OVMF*, which is an open-source UEFI implementation. footnote:[See the OVMF Project https://github.com/tianocore/tianocore.github.io/wiki/OVMF]
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740
741If you want to use OVMF, there are several things to consider:
742
743In order to save things like the *boot order*, there needs to be an EFI Disk.
744This disk will be included in backups and snapshots, and there can only be one.
745
746You can create such a disk with the following command:
747
748 qm set <vmid> -efidisk0 <storage>:1,format=<format>
749
750Where *<storage>* is the storage where you want to have the disk, and
751*<format>* is a format which the storage supports. Alternatively, you can
752create such a disk through the web interface with 'Add' -> 'EFI Disk' in the
753hardware section of a VM.
754
755When using OVMF with a virtual display (without VGA passthrough),
756you need to set the client resolution in the OVMF menu(which you can reach
757with a press of the ESC button during boot), or you have to choose
758SPICE as the display type.
759
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760[[qm_ivshmem]]
761Inter-VM shared memory
762~~~~~~~~~~~~~~~~~~~~~~
763
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764You can add an Inter-VM shared memory device (`ivshmem`), which allows one to
765share memory between the host and a guest, or also between multiple guests.
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766
767To add such a device, you can use `qm`:
768
769 qm set <vmid> -ivshmem size=32,name=foo
770
771Where the size is in MiB. The file will be located under
772`/dev/shm/pve-shm-$name` (the default name is the vmid).
773
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774NOTE: Currently the device will get deleted as soon as any VM using it got
775shutdown or stopped. Open connections will still persist, but new connections
776to the exact same device cannot be made anymore.
777
8861c7ad 778A use case for such a device is the Looking Glass
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779footnote:[Looking Glass: https://looking-glass.io/] project, which enables high
780performance, low-latency display mirroring between host and guest.
0ad30983 781
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782[[qm_audio_device]]
783Audio Device
784~~~~~~~~~~~~
785
786To add an audio device run the following command:
787
788----
789qm set <vmid> -audio0 device=<device>
790----
791
792Supported audio devices are:
793
794* `ich9-intel-hda`: Intel HD Audio Controller, emulates ICH9
795* `intel-hda`: Intel HD Audio Controller, emulates ICH6
796* `AC97`: Audio Codec '97, useful for older operating systems like Windows XP
797
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798There are two backends available:
799
800* 'spice'
801* 'none'
802
803The 'spice' backend can be used in combination with xref:qm_display[SPICE] while
804the 'none' backend can be useful if an audio device is needed in the VM for some
805software to work. To use the physical audio device of the host use device
806passthrough (see xref:qm_pci_passthrough[PCI Passthrough] and
807xref:qm_usb_passthrough[USB Passthrough]). Remote protocols like Microsoft’s RDP
808have options to play sound.
809
ca8c3009 810
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811[[qm_virtio_rng]]
812VirtIO RNG
813~~~~~~~~~~
814
815A RNG (Random Number Generator) is a device providing entropy ('randomness') to
816a system. A virtual hardware-RNG can be used to provide such entropy from the
817host system to a guest VM. This helps to avoid entropy starvation problems in
818the guest (a situation where not enough entropy is available and the system may
819slow down or run into problems), especially during the guests boot process.
820
821To add a VirtIO-based emulated RNG, run the following command:
822
823----
824qm set <vmid> -rng0 source=<source>[,max_bytes=X,period=Y]
825----
826
827`source` specifies where entropy is read from on the host and has to be one of
828the following:
829
830* `/dev/urandom`: Non-blocking kernel entropy pool (preferred)
831* `/dev/random`: Blocking kernel pool (not recommended, can lead to entropy
832 starvation on the host system)
833* `/dev/hwrng`: To pass through a hardware RNG attached to the host (if multiple
834 are available, the one selected in
835 `/sys/devices/virtual/misc/hw_random/rng_current` will be used)
836
837A limit can be specified via the `max_bytes` and `period` parameters, they are
838read as `max_bytes` per `period` in milliseconds. However, it does not represent
839a linear relationship: 1024B/1000ms would mean that up to 1 KiB of data becomes
840available on a 1 second timer, not that 1 KiB is streamed to the guest over the
841course of one second. Reducing the `period` can thus be used to inject entropy
842into the guest at a faster rate.
843
844By default, the limit is set to 1024 bytes per 1000 ms (1 KiB/s). It is
845recommended to always use a limiter to avoid guests using too many host
846resources. If desired, a value of '0' for `max_bytes` can be used to disable
847all limits.
848
777cf894 849[[qm_bootorder]]
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850Device Boot Order
851~~~~~~~~~~~~~~~~~
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852
853QEMU can tell the guest which devices it should boot from, and in which order.
854This can be specified in the config via the `boot` property, e.g.:
855
856----
857boot: order=scsi0;net0;hostpci0
858----
859
860[thumbnail="screenshot/gui-qemu-edit-bootorder.png"]
861
862This way, the guest would first attempt to boot from the disk `scsi0`, if that
863fails, it would go on to attempt network boot from `net0`, and in case that
864fails too, finally attempt to boot from a passed through PCIe device (seen as
865disk in case of NVMe, otherwise tries to launch into an option ROM).
866
867On the GUI you can use a drag-and-drop editor to specify the boot order, and use
868the checkbox to enable or disable certain devices for booting altogether.
869
870NOTE: If your guest uses multiple disks to boot the OS or load the bootloader,
871all of them must be marked as 'bootable' (that is, they must have the checkbox
872enabled or appear in the list in the config) for the guest to be able to boot.
873This is because recent SeaBIOS and OVMF versions only initialize disks if they
874are marked 'bootable'.
875
876In any case, even devices not appearing in the list or having the checkmark
877disabled will still be available to the guest, once it's operating system has
878booted and initialized them. The 'bootable' flag only affects the guest BIOS and
879bootloader.
880
881
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882[[qm_startup_and_shutdown]]
883Automatic Start and Shutdown of Virtual Machines
884~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
885
886After creating your VMs, you probably want them to start automatically
887when the host system boots. For this you need to select the option 'Start at
888boot' from the 'Options' Tab of your VM in the web interface, or set it with
889the following command:
890
891 qm set <vmid> -onboot 1
892
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893.Start and Shutdown Order
894
1ff5e4e8 895[thumbnail="screenshot/gui-qemu-edit-start-order.png"]
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896
897In some case you want to be able to fine tune the boot order of your
898VMs, for instance if one of your VM is providing firewalling or DHCP
899to other guest systems. For this you can use the following
900parameters:
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901
902* *Start/Shutdown order*: Defines the start order priority. E.g. set it to 1 if
903you want the VM to be the first to be started. (We use the reverse startup
904order for shutdown, so a machine with a start order of 1 would be the last to
7eed72d8 905be shut down). If multiple VMs have the same order defined on a host, they will
d750c851 906additionally be ordered by 'VMID' in ascending order.
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907* *Startup delay*: Defines the interval between this VM start and subsequent
908VMs starts . E.g. set it to 240 if you want to wait 240 seconds before starting
909other VMs.
910* *Shutdown timeout*: Defines the duration in seconds {pve} should wait
911for the VM to be offline after issuing a shutdown command.
7eed72d8 912By default this value is set to 180, which means that {pve} will issue a
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913shutdown request and wait 180 seconds for the machine to be offline. If
914the machine is still online after the timeout it will be stopped forcefully.
288e3f46 915
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916NOTE: VMs managed by the HA stack do not follow the 'start on boot' and
917'boot order' options currently. Those VMs will be skipped by the startup and
918shutdown algorithm as the HA manager itself ensures that VMs get started and
919stopped.
920
288e3f46 921Please note that machines without a Start/Shutdown order parameter will always
7eed72d8 922start after those where the parameter is set. Further, this parameter can only
d750c851 923be enforced between virtual machines running on the same host, not
288e3f46 924cluster-wide.
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926
927[[qm_qemu_agent]]
928Qemu Guest Agent
929~~~~~~~~~~~~~~~~
930
931The Qemu Guest Agent is a service which runs inside the VM, providing a
932communication channel between the host and the guest. It is used to exchange
933information and allows the host to issue commands to the guest.
934
935For example, the IP addresses in the VM summary panel are fetched via the guest
936agent.
937
938Or when starting a backup, the guest is told via the guest agent to sync
939outstanding writes via the 'fs-freeze' and 'fs-thaw' commands.
940
941For the guest agent to work properly the following steps must be taken:
942
943* install the agent in the guest and make sure it is running
944* enable the communication via the agent in {pve}
945
946Install Guest Agent
947^^^^^^^^^^^^^^^^^^^
948
949For most Linux distributions, the guest agent is available. The package is
950usually named `qemu-guest-agent`.
951
952For Windows, it can be installed from the
953https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso[Fedora
954VirtIO driver ISO].
955
956Enable Guest Agent Communication
957^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
958
959Communication from {pve} with the guest agent can be enabled in the VM's
960*Options* panel. A fresh start of the VM is necessary for the changes to take
961effect.
962
963It is possible to enable the 'Run guest-trim' option. With this enabled,
964{pve} will issue a trim command to the guest after the following
965operations that have the potential to write out zeros to the storage:
966
967* moving a disk to another storage
968* live migrating a VM to another node with local storage
969
970On a thin provisioned storage, this can help to free up unused space.
971
972Troubleshooting
973^^^^^^^^^^^^^^^
974
975.VM does not shut down
976
977Make sure the guest agent is installed and running.
978
979Once the guest agent is enabled, {pve} will send power commands like
980'shutdown' via the guest agent. If the guest agent is not running, commands
981cannot get executed properly and the shutdown command will run into a timeout.
982
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983[[qm_spice_enhancements]]
984SPICE Enhancements
985~~~~~~~~~~~~~~~~~~
986
987SPICE Enhancements are optional features that can improve the remote viewer
988experience.
989
990To enable them via the GUI go to the *Options* panel of the virtual machine. Run
991the following command to enable them via the CLI:
992
993----
994qm set <vmid> -spice_enhancements foldersharing=1,videostreaming=all
995----
996
997NOTE: To use these features the <<qm_display,*Display*>> of the virtual machine
998must be set to SPICE (qxl).
999
1000Folder Sharing
1001^^^^^^^^^^^^^^
1002
1003Share a local folder with the guest. The `spice-webdavd` daemon needs to be
1004installed in the guest. It makes the shared folder available through a local
1005WebDAV server located at http://localhost:9843.
1006
1007For Windows guests the installer for the 'Spice WebDAV daemon' can be downloaded
1008from the
1009https://www.spice-space.org/download.html#windows-binaries[official SPICE website].
1010
1011Most Linux distributions have a package called `spice-webdavd` that can be
1012installed.
1013
1014To share a folder in Virt-Viewer (Remote Viewer) go to 'File -> Preferences'.
1015Select the folder to share and then enable the checkbox.
1016
1017NOTE: Folder sharing currently only works in the Linux version of Virt-Viewer.
1018
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1019CAUTION: Experimental! Currently this feature does not work reliably.
1020
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1021Video Streaming
1022^^^^^^^^^^^^^^^
1023
1024Fast refreshing areas are encoded into a video stream. Two options exist:
1025
1026* *all*: Any fast refreshing area will be encoded into a video stream.
1027* *filter*: Additional filters are used to decide if video streaming should be
1028 used (currently only small window surfaces are skipped).
1029
1030A general recommendation if video streaming should be enabled and which option
1031to choose from cannot be given. Your mileage may vary depending on the specific
1032circumstances.
1033
1034Troubleshooting
1035^^^^^^^^^^^^^^^
1036
19a58e02 1037.Shared folder does not show up
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1038
1039Make sure the WebDAV service is enabled and running in the guest. On Windows it
1040is called 'Spice webdav proxy'. In Linux the name is 'spice-webdavd' but can be
1041different depending on the distribution.
1042
1043If the service is running, check the WebDAV server by opening
1044http://localhost:9843 in a browser in the guest.
1045
1046It can help to restart the SPICE session.
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1047
1048[[qm_migration]]
1049Migration
1050---------
1051
1ff5e4e8 1052[thumbnail="screenshot/gui-qemu-migrate.png"]
e4bcef0a 1053
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1054If you have a cluster, you can migrate your VM to another host with
1055
1056 qm migrate <vmid> <target>
1057
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1058There are generally two mechanisms for this
1059
1060* Online Migration (aka Live Migration)
1061* Offline Migration
1062
1063Online Migration
1064~~~~~~~~~~~~~~~~
1065
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1066When your VM is running and it has no local resources defined (such as disks
1067on local storage, passed through devices, etc.) you can initiate a live
1068migration with the -online flag.
1069
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1070How it works
1071^^^^^^^^^^^^
1072
1073This starts a Qemu Process on the target host with the 'incoming' flag, which
1074means that the process starts and waits for the memory data and device states
1075from the source Virtual Machine (since all other resources, e.g. disks,
1076are shared, the memory content and device state are the only things left
1077to transmit).
1078
1079Once this connection is established, the source begins to send the memory
1080content asynchronously to the target. If the memory on the source changes,
1081those sections are marked dirty and there will be another pass of sending data.
1082This happens until the amount of data to send is so small that it can
1083pause the VM on the source, send the remaining data to the target and start
1084the VM on the target in under a second.
1085
1086Requirements
1087^^^^^^^^^^^^
1088
1089For Live Migration to work, there are some things required:
1090
1091* The VM has no local resources (e.g. passed through devices, local disks, etc.)
1092* The hosts are in the same {pve} cluster.
1093* The hosts have a working (and reliable) network connection.
1094* The target host must have the same or higher versions of the
1095 {pve} packages. (It *might* work the other way, but this is never guaranteed)
1096
1097Offline Migration
1098~~~~~~~~~~~~~~~~~
1099
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1100If you have local resources, you can still offline migrate your VMs,
1101as long as all disk are on storages, which are defined on both hosts.
1102Then the migration will copy the disk over the network to the target host.
1103
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1104[[qm_copy_and_clone]]
1105Copies and Clones
1106-----------------
9e55c76d 1107
1ff5e4e8 1108[thumbnail="screenshot/gui-qemu-full-clone.png"]
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1109
1110VM installation is usually done using an installation media (CD-ROM)
1111from the operation system vendor. Depending on the OS, this can be a
1112time consuming task one might want to avoid.
1113
1114An easy way to deploy many VMs of the same type is to copy an existing
1115VM. We use the term 'clone' for such copies, and distinguish between
1116'linked' and 'full' clones.
1117
1118Full Clone::
1119
1120The result of such copy is an independent VM. The
1121new VM does not share any storage resources with the original.
1122+
707e37a2 1123
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1124It is possible to select a *Target Storage*, so one can use this to
1125migrate a VM to a totally different storage. You can also change the
1126disk image *Format* if the storage driver supports several formats.
1127+
707e37a2 1128
730fbca4 1129NOTE: A full clone needs to read and copy all VM image data. This is
9e55c76d 1130usually much slower than creating a linked clone.
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1131+
1132
1133Some storage types allows to copy a specific *Snapshot*, which
1134defaults to the 'current' VM data. This also means that the final copy
1135never includes any additional snapshots from the original VM.
1136
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1137
1138Linked Clone::
1139
730fbca4 1140Modern storage drivers support a way to generate fast linked
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1141clones. Such a clone is a writable copy whose initial contents are the
1142same as the original data. Creating a linked clone is nearly
1143instantaneous, and initially consumes no additional space.
1144+
707e37a2 1145
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1146They are called 'linked' because the new image still refers to the
1147original. Unmodified data blocks are read from the original image, but
1148modification are written (and afterwards read) from a new
1149location. This technique is called 'Copy-on-write'.
1150+
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1151
1152This requires that the original volume is read-only. With {pve} one
1153can convert any VM into a read-only <<qm_templates, Template>>). Such
1154templates can later be used to create linked clones efficiently.
1155+
1156
730fbca4
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1157NOTE: You cannot delete an original template while linked clones
1158exist.
9e55c76d 1159+
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1160
1161It is not possible to change the *Target storage* for linked clones,
1162because this is a storage internal feature.
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1163
1164
1165The *Target node* option allows you to create the new VM on a
1166different node. The only restriction is that the VM is on shared
1167storage, and that storage is also available on the target node.
1168
730fbca4 1169To avoid resource conflicts, all network interface MAC addresses get
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1170randomized, and we generate a new 'UUID' for the VM BIOS (smbios1)
1171setting.
1172
1173
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1174[[qm_templates]]
1175Virtual Machine Templates
1176-------------------------
1177
1178One can convert a VM into a Template. Such templates are read-only,
1179and you can use them to create linked clones.
1180
1181NOTE: It is not possible to start templates, because this would modify
1182the disk images. If you want to change the template, create a linked
1183clone and modify that.
1184
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1185VM Generation ID
1186----------------
1187
941ff8d3 1188{pve} supports Virtual Machine Generation ID ('vmgenid') footnote:[Official
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1189'vmgenid' Specification
1190https://docs.microsoft.com/en-us/windows/desktop/hyperv_v2/virtual-machine-generation-identifier]
1191for virtual machines.
1192This can be used by the guest operating system to detect any event resulting
1193in a time shift event, for example, restoring a backup or a snapshot rollback.
319d5325 1194
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1195When creating new VMs, a 'vmgenid' will be automatically generated and saved
1196in its configuration file.
319d5325 1197
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1198To create and add a 'vmgenid' to an already existing VM one can pass the
1199special value `1' to let {pve} autogenerate one or manually set the 'UUID'
1200footnote:[Online GUID generator http://guid.one/] by using it as value,
1201e.g.:
319d5325 1202
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1203----
1204 qm set VMID -vmgenid 1
1205 qm set VMID -vmgenid 00000000-0000-0000-0000-000000000000
1206----
319d5325 1207
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1208NOTE: The initial addition of a 'vmgenid' device to an existing VM, may result
1209in the same effects as a change on snapshot rollback, backup restore, etc., has
1210as the VM can interpret this as generation change.
1211
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1212In the rare case the 'vmgenid' mechanism is not wanted one can pass `0' for
1213its value on VM creation, or retroactively delete the property in the
1214configuration with:
319d5325 1215
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1216----
1217 qm set VMID -delete vmgenid
1218----
319d5325 1219
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1220The most prominent use case for 'vmgenid' are newer Microsoft Windows
1221operating systems, which use it to avoid problems in time sensitive or
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1222replicate services (e.g., databases, domain controller
1223footnote:[https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/get-started/virtual-dc/virtualized-domain-controller-architecture])
1224on snapshot rollback, backup restore or a whole VM clone operation.
319d5325 1225
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1226Importing Virtual Machines and disk images
1227------------------------------------------
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1228
1229A VM export from a foreign hypervisor takes usually the form of one or more disk
59552707 1230 images, with a configuration file describing the settings of the VM (RAM,
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1231 number of cores). +
1232The disk images can be in the vmdk format, if the disks come from
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1233VMware or VirtualBox, or qcow2 if the disks come from a KVM hypervisor.
1234The most popular configuration format for VM exports is the OVF standard, but in
1235practice interoperation is limited because many settings are not implemented in
1236the standard itself, and hypervisors export the supplementary information
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1237in non-standard extensions.
1238
1239Besides the problem of format, importing disk images from other hypervisors
1240may fail if the emulated hardware changes too much from one hypervisor to
1241another. Windows VMs are particularly concerned by this, as the OS is very
1242picky about any changes of hardware. This problem may be solved by
1243installing the MergeIDE.zip utility available from the Internet before exporting
1244and choosing a hard disk type of *IDE* before booting the imported Windows VM.
1245
59552707 1246Finally there is the question of paravirtualized drivers, which improve the
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1247speed of the emulated system and are specific to the hypervisor.
1248GNU/Linux and other free Unix OSes have all the necessary drivers installed by
1249default and you can switch to the paravirtualized drivers right after importing
59552707 1250the VM. For Windows VMs, you need to install the Windows paravirtualized
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1251drivers by yourself.
1252
1253GNU/Linux and other free Unix can usually be imported without hassle. Note
eb01c5cf 1254that we cannot guarantee a successful import/export of Windows VMs in all
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1255cases due to the problems above.
1256
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1257Step-by-step example of a Windows OVF import
1258~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
56368da8 1259
59552707 1260Microsoft provides
c069256d 1261https://developer.microsoft.com/en-us/windows/downloads/virtual-machines/[Virtual Machines downloads]
144d5ede 1262 to get started with Windows development.We are going to use one of these
c069256d 1263to demonstrate the OVF import feature.
56368da8 1264
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1265Download the Virtual Machine zip
1266^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
56368da8 1267
144d5ede 1268After getting informed about the user agreement, choose the _Windows 10
c069256d 1269Enterprise (Evaluation - Build)_ for the VMware platform, and download the zip.
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1270
1271Extract the disk image from the zip
1272^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1273
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1274Using the `unzip` utility or any archiver of your choice, unpack the zip,
1275and copy via ssh/scp the ovf and vmdk files to your {pve} host.
56368da8 1276
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1277Import the Virtual Machine
1278^^^^^^^^^^^^^^^^^^^^^^^^^^
56368da8 1279
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1280This will create a new virtual machine, using cores, memory and
1281VM name as read from the OVF manifest, and import the disks to the +local-lvm+
1282 storage. You have to configure the network manually.
56368da8 1283
c069256d 1284 qm importovf 999 WinDev1709Eval.ovf local-lvm
56368da8 1285
c069256d 1286The VM is ready to be started.
56368da8 1287
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1288Adding an external disk image to a Virtual Machine
1289~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
56368da8 1290
144d5ede 1291You can also add an existing disk image to a VM, either coming from a
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1292foreign hypervisor, or one that you created yourself.
1293
1294Suppose you created a Debian/Ubuntu disk image with the 'vmdebootstrap' tool:
1295
1296 vmdebootstrap --verbose \
67d59a35 1297 --size 10GiB --serial-console \
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1298 --grub --no-extlinux \
1299 --package openssh-server \
1300 --package avahi-daemon \
1301 --package qemu-guest-agent \
1302 --hostname vm600 --enable-dhcp \
1303 --customize=./copy_pub_ssh.sh \
1304 --sparse --image vm600.raw
1305
1306You can now create a new target VM for this image.
1307
1308 qm create 600 --net0 virtio,bridge=vmbr0 --name vm600 --serial0 socket \
1309 --bootdisk scsi0 --scsihw virtio-scsi-pci --ostype l26
56368da8 1310
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1311Add the disk image as +unused0+ to the VM, using the storage +pvedir+:
1312
1313 qm importdisk 600 vm600.raw pvedir
1314
1315Finally attach the unused disk to the SCSI controller of the VM:
1316
1317 qm set 600 --scsi0 pvedir:600/vm-600-disk-1.raw
1318
1319The VM is ready to be started.
707e37a2 1320
7eb69fd2 1321
16b4185a 1322ifndef::wiki[]
7eb69fd2 1323include::qm-cloud-init.adoc[]
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1324endif::wiki[]
1325
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1326ifndef::wiki[]
1327include::qm-pci-passthrough.adoc[]
1328endif::wiki[]
16b4185a 1329
c2c8eb89 1330Hookscripts
91f416b7 1331-----------
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1332
1333You can add a hook script to VMs with the config property `hookscript`.
1334
c961e4cc 1335 qm set 100 --hookscript local:snippets/hookscript.pl
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1336
1337It will be called during various phases of the guests lifetime.
1338For an example and documentation see the example script under
1339`/usr/share/pve-docs/examples/guest-example-hookscript.pl`.
7eb69fd2 1340
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1341[[qm_hibernate]]
1342Hibernation
1343-----------
1344
1345You can suspend a VM to disk with the GUI option `Hibernate` or with
1346
1347 qm suspend ID --todisk
1348
1349That means that the current content of the memory will be saved onto disk
1350and the VM gets stopped. On the next start, the memory content will be
1351loaded and the VM can continue where it was left off.
1352
1353[[qm_vmstatestorage]]
1354.State storage selection
1355If no target storage for the memory is given, it will be automatically
1356chosen, the first of:
1357
13581. The storage `vmstatestorage` from the VM config.
13592. The first shared storage from any VM disk.
13603. The first non-shared storage from any VM disk.
13614. The storage `local` as a fallback.
1362
8c1189b6 1363Managing Virtual Machines with `qm`
dd042288 1364------------------------------------
f69cfd23 1365
dd042288 1366qm is the tool to manage Qemu/Kvm virtual machines on {pve}. You can
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1367create and destroy virtual machines, and control execution
1368(start/stop/suspend/resume). Besides that, you can use qm to set
1369parameters in the associated config file. It is also possible to
1370create and delete virtual disks.
1371
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1372CLI Usage Examples
1373~~~~~~~~~~~~~~~~~~
1374
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1375Using an iso file uploaded on the 'local' storage, create a VM
1376with a 4 GB IDE disk on the 'local-lvm' storage
dd042288 1377
b01b1f2c 1378 qm create 300 -ide0 local-lvm:4 -net0 e1000 -cdrom local:iso/proxmox-mailgateway_2.1.iso
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1379
1380Start the new VM
1381
1382 qm start 300
1383
1384Send a shutdown request, then wait until the VM is stopped.
1385
1386 qm shutdown 300 && qm wait 300
1387
1388Same as above, but only wait for 40 seconds.
1389
1390 qm shutdown 300 && qm wait 300 -timeout 40
1391
87927c65
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1392Destroying a VM always removes it from Access Control Lists and it always
1393removes the firewall configuration of the VM. You have to activate
1394'--purge', if you want to additionally remove the VM from replication jobs,
1395backup jobs and HA resource configurations.
1396
1397 qm destroy 300 --purge
1398
1399
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1400
1401[[qm_configuration]]
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1402Configuration
1403-------------
1404
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1405VM configuration files are stored inside the Proxmox cluster file
1406system, and can be accessed at `/etc/pve/qemu-server/<VMID>.conf`.
1407Like other files stored inside `/etc/pve/`, they get automatically
1408replicated to all other cluster nodes.
f69cfd23 1409
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1410NOTE: VMIDs < 100 are reserved for internal purposes, and VMIDs need to be
1411unique cluster wide.
1412
1413.Example VM Configuration
1414----
777cf894 1415boot: order=virtio0;net0
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1416cores: 1
1417sockets: 1
1418memory: 512
1419name: webmail
1420ostype: l26
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1421net0: e1000=EE:D2:28:5F:B6:3E,bridge=vmbr0
1422virtio0: local:vm-100-disk-1,size=32G
1423----
1424
1425Those configuration files are simple text files, and you can edit them
1426using a normal text editor (`vi`, `nano`, ...). This is sometimes
1427useful to do small corrections, but keep in mind that you need to
1428restart the VM to apply such changes.
1429
1430For that reason, it is usually better to use the `qm` command to
1431generate and modify those files, or do the whole thing using the GUI.
1432Our toolkit is smart enough to instantaneously apply most changes to
1433running VM. This feature is called "hot plug", and there is no
1434need to restart the VM in that case.
1435
1436
1437File Format
1438~~~~~~~~~~~
1439
1440VM configuration files use a simple colon separated key/value
1441format. Each line has the following format:
1442
1443-----
1444# this is a comment
1445OPTION: value
1446-----
1447
1448Blank lines in those files are ignored, and lines starting with a `#`
1449character are treated as comments and are also ignored.
1450
1451
1452[[qm_snapshots]]
1453Snapshots
1454~~~~~~~~~
1455
1456When you create a snapshot, `qm` stores the configuration at snapshot
1457time into a separate snapshot section within the same configuration
1458file. For example, after creating a snapshot called ``testsnapshot'',
1459your configuration file will look like this:
1460
1461.VM configuration with snapshot
1462----
1463memory: 512
1464swap: 512
1465parent: testsnaphot
1466...
1467
1468[testsnaphot]
1469memory: 512
1470swap: 512
1471snaptime: 1457170803
1472...
1473----
1474
1475There are a few snapshot related properties like `parent` and
1476`snaptime`. The `parent` property is used to store the parent/child
1477relationship between snapshots. `snaptime` is the snapshot creation
1478time stamp (Unix epoch).
f69cfd23 1479
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1480You can optionally save the memory of a running VM with the option `vmstate`.
1481For details about how the target storage gets chosen for the VM state, see
1482xref:qm_vmstatestorage[State storage selection] in the chapter
1483xref:qm_hibernate[Hibernation].
f69cfd23 1484
80c0adcb 1485[[qm_options]]
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1486Options
1487~~~~~~~
1488
1489include::qm.conf.5-opts.adoc[]
1490
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1491
1492Locks
1493-----
1494
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1495Online migrations, snapshots and backups (`vzdump`) set a lock to
1496prevent incompatible concurrent actions on the affected VMs. Sometimes
1497you need to remove such a lock manually (e.g., after a power failure).
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1498
1499 qm unlock <vmid>
1500
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1501CAUTION: Only do that if you are sure the action which set the lock is
1502no longer running.
1503
f69cfd23 1504
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1505ifdef::wiki[]
1506
1507See Also
1508~~~~~~~~
1509
1510* link:/wiki/Cloud-Init_Support[Cloud-Init Support]
1511
1512endif::wiki[]
1513
1514
f69cfd23 1515ifdef::manvolnum[]
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1516
1517Files
1518------
1519
1520`/etc/pve/qemu-server/<VMID>.conf`::
1521
1522Configuration file for the VM '<VMID>'.
1523
1524
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1525include::pve-copyright.adoc[]
1526endif::manvolnum[]