virt-what - Online in the Cloud

PROGRAM:

NAME

virt-what - detect if we are running in a virtual machine

SUMMARY

virt-what [options]

DESCRIPTION

"virt-what" is a shell script which can be used to detect if the program is running in a
virtual machine.

The program prints out a list of "facts" about the virtual machine, derived from
heuristics. One fact is printed per line.

If nothing is printed and the script exits with code 0 (no error), then it can mean either
that the program is running on bare-metal or the program is running inside a type of
virtual machine which we don't know about or cannot detect.

FACTS

hyperv
This is Microsoft Hyper-V hypervisor.

Status: confirmed by RWMJ

ibm_systemz
This is an IBM SystemZ (or other S/390) hardware partitioning system. Additional
facts listed below may also be printed.

ibm_systemz-direct
This is Linux running directly on a IBM SystemZ hardware partitioning system.

This is expected to be a highly unusual configuration - if you see this result you
should treat it with suspicion.

Status: not confirmed

ibm_systemz-lpar
This is Linux running directly on an LPAR on an IBM SystemZ hardware partitioning
system.

Status: not confirmed

ibm_systemz-zvm
This is a z/VM guest running in an LPAR on an IBM SystemZ hardware partitioning
system.

Status: confirmed by RWMJ using a Fedora guest running in z/VM

linux_vserver
This is printed for backwards compatibility with older virt-what which could not
distinguish between a Linux VServer container guest and host.

linux_vserver-guest
This process is running in a Linux VServer container.

Status: contributed by BarXX Metin

linux_vserver-host
This process is running as the Linux VServer host (VxID 0).

Status: contributed by BarXX Metin and Elan Ruusamaee

lxc This process is running in a Linux LXC container.

Status: contributed by Marc Fournier

kvm This guest is running on the KVM hypervisor using hardware acceleration.

Note that if the hypervisor is using software acceleration you should not see this,
but should see the "qemu" fact instead.

Status: confirmed by RWMJ.

openvz
The guest appears to be running inside an OpenVZ or Virtuozzo container.

Status: contributed by Evgeniy Sokolov

parallels
The guest is running inside Parallels Virtual Platform (Parallels Desktop, Parallels
Server).

Status: contributed by Justin Clift

powervm_lx86
The guest is running inside IBM PowerVM Lx86 Linux/x86 emulator.

Status: data originally supplied by Jeffrey Scheel, confimed by Yufang Zhang and RWMJ

qemu
This is QEMU hypervisor using software emulation.

Note that for KVM (hardware accelerated) guests you should not see this.

Status: confirmed by RWMJ.

uml This is a User-Mode Linux (UML) guest.

Status: contributed by Laurent Leonard

virt
Some sort of virtualization appears to be present, but we are not sure what it is. In
some very rare corner cases where we know that virtualization is hard to detect, we
will try a timing attack to see if certain machine instructions are running much more
slowly than they should be, which would indicate virtualization. In this case, the
generic fact "virt" is printed.

virtage
This is Hitachi Virtualization Manager (HVM) Virtage hardware partitioning system.

Status: data supplied by Bhavna Sarathy, not confirmed

virtualbox
This is a VirtualBox guest.

Status: contributed by Laurent Leonard

virtualpc
The guest appears to be running on Microsoft VirtualPC.

Status: not confirmed

vmware
The guest appears to be running on VMware hypervisor.

Status: confirmed by RWMJ

xen The guest appears to be running on Xen hypervisor.

Status: confirmed by RWMJ

xen-dom0
This is the Xen dom0 (privileged domain).

Status: confirmed by RWMJ

xen-domU
This is a Xen domU (paravirtualized guest domain).

Status: confirmed by RWMJ

xen-hvm
This is a Xen guest fully virtualized (HVM).

Status: confirmed by RWMJ

EXIT STATUS

Programs that use or wrap "virt-what" should check that the exit status is 0 before they
attempt to parse the output of the command.

A non-zero exit status indicates some error, for example, an unrecognized command line
argument. If the exit status is non-zero then the output "facts" (if any were printed)
cannot be guaranteed and should be ignored.

The exit status does not have anything to do with whether the program is running on
baremetal or under virtualization, nor with whether "virt-what" managed detection
"correctly" (which is basically unknowable given the large variety of virtualization
systems out there and that some systems deliberately emulate others).

RUNNING VIRT-WHAT FROM OTHER PROGRAMS

"virt-what" is designed so that you can easily run it from other programs or wrap it up in
a library.

Your program should check the exit status (see the section above).

Some programming languages (notably Python: issue 1652) erroneously mask the "SIGPIPE"
signal and do not restore it when executing subprocesses. "virt-what" is a shell script
and some shell commands do not work correctly when you do this. You may see warnings from
"virt-what" similar to this:

echo: write error: Broken pipe

The solution is to set the "SIGPIPE" signal handler back to "SIG_DFL" before running
"virt-what".

IMPORTANT NOTE

Most of the time, using this program is the wrong thing to do. Instead you should detect
the specific features you actually want to use. (As an example, if you wanted to issue
Xen hypervisor commands you would look for the "/proc/xen/privcmd" file).

However people keep asking for this, so we provide it. There are a few legitimate uses:

Bug reporting tool
If you think that virtualization could affect how your program runs, then you might
use "virt-what" to report this in a bug reporting tool.

Status display and monitoring tools
You might include this information in status and monitoring programs.

System tuning (sometimes)
You might use this program to tune an operating system so it runs better as a virtual
machine of a particular hypervisor. However if installing paravirtualized drivers,
it's better to check for the specific features your drivers need (eg. for the presence
of PCI devices).

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