Downburst VMs

Teuthology also supports virtual machines via downburst, which can function like physical machines but differ in the following ways:

VPS Hosts:

The following description is based on the Red Hat lab used by the upstream Ceph development and quality assurance teams.

The teuthology database of available machines contains a vpshost field. For physical machines, this value is null. For virtual machines, this entry is the name of the physical machine that that virtual machine resides on.

There are fixed “slots” for virtual machines that appear in the teuthology database. These slots have a machine type of vps and can be locked like any other machine. The existence of a vpshost field is how teuthology knows whether or not a database entry represents a physical or a virtual machine.

In order to get the right virtual machine associations, the following needs to be set in ~/.config/libvirt/libvirt.conf or for some older versions of libvirt (like ubuntu precise) in ~/.libvirt/libvirt.conf:

uri_aliases = [


When a virtual machine is locked, downburst is run on that machine to install a new image. This allows the user to set different virtual OSes to be installed on the newly created virtual machine. Currently the default virtual machine is ubuntu (precise). A different vm installation can be set using the --os-type and --os-version options in teuthology.lock.

When a virtual machine is unlocked, downburst destroys the image on the machine.

To find the downburst executable, teuthology first checks the PATH environment variable. If not defined, teuthology next checks for src/downburst/virtualenv/bin/downburst executables in the user’s home directory, /home/ubuntu, and /home/teuthology. This can all be overridden if the user specifies a downburst field in the user’s .teuthology.yaml file.

Host Keys:

Because teuthology reinstalls a new machine, a new hostkey is generated. After locking, once a connection is established to the new machine, teuthology-lock with the --list or --list-targets options will display the new keys. When vps machines are locked using the --lock-many option, a message is displayed indicating that --list-targets should be run later.


It is assumed that downburst is on the user’s $PATH.