default https://en.wikipedia.org/wiki/Intel_440FX[Intel 440FX] or the
https://ark.intel.com/content/www/us/en/ark/products/31918/intel-82q35-graphics-and-memory-controller.html[Q35]
chipset, which also provides a virtual PCIe bus, and thus may be desired if
-one want's to pass through PCIe hardware.
+one wants to pass through PCIe hardware.
[[qm_hard_disk]]
Hard Disk
*VirtIO* controller, or with the *SCSI* controller, when the emulated controller
type is *VirtIO SCSI single*.
With this enabled, Qemu creates one I/O thread per storage controller,
-instead of a single thread for all I/O, so it can increase performance when
-multiple isks are used and each disk has its own storage controller.
+rather than a single thread for all I/O. This can increase performance when
+multiple disks are used and each disk has its own storage controller.
[[qm_cpu]]
cores on a machine with only 8 cores). In that case the host system will
balance the Qemu execution threads between your server cores, just like if you
were running a standard multithreaded application. However, {pve} will prevent
-you from assigning more virtual CPU cores than physically available, as this will
-only bring the performance down due to the cost of context switches.
+you from starting VMs with more virtual CPU cores than physically available, as
+this will only bring the performance down due to the cost of context switches.
[[qm_cpu_resource_limits]]
Resource Limits
cluster where all nodes have the same CPU, set the CPU type to host, as in
theory this will give your guests maximum performance.
+Custom CPU Types
+^^^^^^^^^^^^^^^^
+
+You can specify custom CPU types with a configurable set of features. These are
+maintained in the configuration file `/etc/pve/virtual-guest/cpu-models.conf` by
+an administrator. See `man cpu-models.conf` for format details.
+
+Specified custom types can be selected by any user with the `Sys.Audit`
+privilege on `/nodes`. When configuring a custom CPU type for a VM via the CLI
+or API, the name needs to be prefixed with 'custom-'.
+
Meltdown / Spectre related CPU flags
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
xref:qm_pci_passthrough[PCI Passthrough] and
xref:qm_usb_passthrough[USB Passthrough]).
+[[qm_virtio_rng]]
+VirtIO RNG
+~~~~~~~~~~
+
+A RNG (Random Number Generator) is a device providing entropy ('randomness') to
+a system. A virtual hardware-RNG can be used to provide such entropy from the
+host system to a guest VM. This helps to avoid entropy starvation problems in
+the guest (a situation where not enough entropy is available and the system may
+slow down or run into problems), especially during the guests boot process.
+
+To add a VirtIO-based emulated RNG, run the following command:
+
+----
+qm set <vmid> -rng0 source=<source>[,max_bytes=X,period=Y]
+----
+
+`source` specifies where entropy is read from on the host and has to be one of
+the following:
+
+* `/dev/urandom`: Non-blocking kernel entropy pool (preferred)
+* `/dev/random`: Blocking kernel pool (not recommended, can lead to entropy
+ starvation on the host system)
+* `/dev/hwrng`: To pass through a hardware RNG attached to the host (if multiple
+ are available, the one selected in
+ `/sys/devices/virtual/misc/hw_random/rng_current` will be used)
+
+A limit can be specified via the `max_bytes` and `period` parameters, they are
+read as `max_bytes` per `period` in milliseconds. However, it does not represent
+a linear relationship: 1024B/1000ms would mean that up to 1 KiB of data becomes
+available on a 1 second timer, not that 1 KiB is streamed to the guest over the
+course of one second. Reducing the `period` can thus be used to inject entropy
+into the guest at a faster rate.
+
+By default, the limit is set to 1024 bytes per 1000 ms (1 KiB/s). It is
+recommended to always use a limiter to avoid guests using too many host
+resources. If desired, a value of '0' for `max_bytes` can be used to disable
+all limits.
+
+[[qm_bootorder]]
+Device Boot Order
+~~~~~~~~~~~~~~~~~
+
+QEMU can tell the guest which devices it should boot from, and in which order.
+This can be specified in the config via the `boot` property, e.g.:
+
+----
+boot: order=scsi0;net0;hostpci0
+----
+
+[thumbnail="screenshot/gui-qemu-edit-bootorder.png"]
+
+This way, the guest would first attempt to boot from the disk `scsi0`, if that
+fails, it would go on to attempt network boot from `net0`, and in case that
+fails too, finally attempt to boot from a passed through PCIe device (seen as
+disk in case of NVMe, otherwise tries to launch into an option ROM).
+
+On the GUI you can use a drag-and-drop editor to specify the boot order, and use
+the checkbox to enable or disable certain devices for booting altogether.
+
+NOTE: If your guest uses multiple disks to boot the OS or load the bootloader,
+all of them must be marked as 'bootable' (that is, they must have the checkbox
+enabled or appear in the list in the config) for the guest to be able to boot.
+This is because recent SeaBIOS and OVMF versions only initialize disks if they
+are marked 'bootable'.
+
+In any case, even devices not appearing in the list or having the checkmark
+disabled will still be available to the guest, once it's operating system has
+booted and initialized them. The 'bootable' flag only affects the guest BIOS and
+bootloader.
+
+
[[qm_startup_and_shutdown]]
Automatic Start and Shutdown of Virtual Machines
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For an example and documentation see the example script under
`/usr/share/pve-docs/examples/guest-example-hookscript.pl`.
+[[qm_hibernate]]
+Hibernation
+-----------
+
+You can suspend a VM to disk with the GUI option `Hibernate` or with
+
+ qm suspend ID --todisk
+
+That means that the current content of the memory will be saved onto disk
+and the VM gets stopped. On the next start, the memory content will be
+loaded and the VM can continue where it was left off.
+
+[[qm_vmstatestorage]]
+.State storage selection
+If no target storage for the memory is given, it will be automatically
+chosen, the first of:
+
+1. The storage `vmstatestorage` from the VM config.
+2. The first shared storage from any VM disk.
+3. The first non-shared storage from any VM disk.
+4. The storage `local` as a fallback.
+
Managing Virtual Machines with `qm`
------------------------------------
qm shutdown 300 && qm wait 300 -timeout 40
+Destroying a VM always removes it from Access Control Lists and it always
+removes the firewall configuration of the VM. You have to activate
+'--purge', if you want to additionally remove the VM from replication jobs,
+backup jobs and HA resource configurations.
+
+ qm destroy 300 --purge
+
+
[[qm_configuration]]
Configuration
.Example VM Configuration
----
+boot: order=virtio0;net0
cores: 1
sockets: 1
memory: 512
name: webmail
ostype: l26
-bootdisk: virtio0
net0: e1000=EE:D2:28:5F:B6:3E,bridge=vmbr0
virtio0: local:vm-100-disk-1,size=32G
----
relationship between snapshots. `snaptime` is the snapshot creation
time stamp (Unix epoch).
+You can optionally save the memory of a running VM with the option `vmstate`.
+For details about how the target storage gets chosen for the VM state, see
+xref:qm_vmstatestorage[State storage selection] in the chapter
+xref:qm_hibernate[Hibernation].
[[qm_options]]
Options
projects / pve-docs.git / blobdiff