virt-what man page

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

docker
This is a Docker container.

Status: confirmed by Charles Nguyen
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.
lkvm
This guest is running on the KVM hypervisor using hardware acceleration, and the userspace component of the hypervisor is lkvm (a.k.a kvmtool).

Status: contributed by Andrew Jones
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, confirmed 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).

See Also

<http://people.redhat.com/~rjones/virt-w…>, <http://www.vmware.com/>, <http://www.microsoft.com/windows/produc…>, <http://xensource.com/>, <http://bellard.org/qemu/>, <http://kvm.qumranet.com/>, <http://openvz.org/>

Authors

Richard W.M. Jones <rjones @ redhat . com>

Reporting Bugs

Bugs can be viewed on the Red Hat Bugzilla page: <https://bugzilla.redhat.com/>.

If you find a bug in virt-what, please follow these steps to report it:

1. Check for existing bug reports
Go to <https://bugzilla.redhat.com/> and search for similar bugs. Someone may already have reported the same bug, and they may even have fixed it.
2. Capture debug and error messages

Run

virt-what > virt-what.log 2>&1

and keep virt-what.log. It may contain error messages which you should submit with your bug report.

3. Get version of virt-what.

Run

virt-what --version
4. Submit a bug report.
Go to <https://bugzilla.redhat.com/> and enter a new bug. Please describe the problem in as much detail as possible.

Remember to include the version numbers (step 3) and the debug messages file (step 2) and as much other detail as possible.
5. Assign the bug to rjones @ redhat.com
Assign or reassign the bug to rjones @ redhat.com (without the spaces). You can also send me an email with the bug number if you want a faster response.

Info

2015-03-27 virt-what-1.15 Virtualization Support