fence_virt.conf(5)

NAME
fence_virt.conf - configuration file for fence_virtd

DESCRIPTION

The fence_virt.conf file contains configuration information for fence_virtd, a fencing request routing daemon for clusters of virtual machines.

The file is tree-structured. There are parent/child relationships and sibling relationships between the nodes.

  foo {
    bar {
      baz = "1";
    }
  }

There are three primary sections of fence_virt.conf.

SECTIONS

  fence_virtd

This section contains global information about how fence_virtd is to operate. The most important pieces of information are as follows:

listener
    the listener plugin for receiving fencing requests from clients

backend
    the plugin to be used to carry out fencing requests

foreground
    do not fork into the background.

wait_for_init
    wait for the frontend and backends to become available rather than giving up immediately. This replaces wait_for_backend in 0.2.x.

module_path
    the module path to search for plugins

  listeners

This section contains listener-specific configuration information; see the section about listeners below.

  backends

This section contains listener-specific configuration information; see the section about listeners below.

  groups

This section contains static maps of which virtual machines may fence which other virtual machines; see the section about groups below.

LISTENERS

There are various listeners available for fence_virtd, each one handles decoding and authentication of a given fencing request. The following configuration blocks belong in the listeners section of fence_virt.conf

  multicast

key_file
    the shared key file to use (default: /etc/cluster/fence_xvm.key).

hash
    the weakest hashing algorithm allowed for client requests. Clients may send packets with stronger hashes than the one specified, but not weaker ones. (default: sha256, but could be sha1, sha512, or none)

auth
    the hashing algorithm to use for the simplistic challenge-response authentication (default: sha256, but could be sha1, sha512, or none)

family
    the IP family to use (default: ipv4, but may be ipv6)

address
    the multicast address to listen on (default: 225.0.0.12)

port
    the multicast port to listen on (default: 1229)

interface
    interface to listen on. By default, fence_virtd listens on all interfaces. However, this causes problems in some environments where the host computer is used as a gateway.

  serial

The serial listener plugin utilizes libvirt's serial (or VMChannel) mapping to listen for requests. When using the serial listener, it is necessary to add a serial port (preferably pointing to /dev/ttyS1) or a channel (preferably pointing to 10.0.2.179:1229) to the libvirt domain description. Note that only type unix , mode bind serial ports and channels are supported and each VM should have a separate unique socket. Example libvirt XML:

  <serial type='unix'>
    <source mode='bind' path='/sandbox/guests/fence_socket_molly'/>
    <target port='1'/>
  </serial>
  <channel type='unix'>
    <source mode='bind' path='/sandbox/guests/fence_molly_vmchannel'/>
    <target type='guestfwd' address='10.0.2.179' port='1229'/>
  </channel>

uri the URI to use when connecting to libvirt by the serial plugin (optional).

path
    The same directory that is defined for the domain serial port path (From example above: /sandbox/guests). Sockets must reside in this directory in order to be considered valid. This can be used to prevent fence_virtd from using the wrong sockets.

mode
    This selects the type of sockets to register. Valid values are "serial" (default) and "vmchannel".

  tcp
The tcp listener operates similarly to the multicast listener but uses TCP sockets for communication instead of using multicast packets.

key_file
    the shared key file to use (default: /etc/cluster/fence_xvm.key).

hash
    the hashing algorithm to use for packet signing (default: sha256, but could be sha1, sha512, or none)

auth
    the hashing algorithm to use for the simplistic challenge-response authentication (default: sha256, but could be sha1, sha512, or none)

family
    the IP family to use (default: ipv4, but may be ipv6)

address
    the IP address to listen on (default: 127.0.0.1 for IPv4, ::1 for IPv6)

port
    the TCP port to listen on (default: 1229)

  vsock
The vsock listener operates similarly to the multicast listener but uses virtual machine sockets (AF_VSOCK) for communication instead of using multicast packets.

key_file
    the shared key file to use (default: /etc/cluster/fence_xvm.key).

hash
    the hashing algorithm to use for packet signing (default: sha256, but could be sha1, sha512, or none)

auth
    the hashing algorithm to use for the simplistic challenge-response authentication (default: sha256, but could be sha1, sha512, or none)

port
    the vsock port to listen on (default: 1229)

BACKENDS

There are various backends available for fence_virtd, each one handles routing a fencing request to a hypervisor or management tool. The following configuration blocks belong in the backends section of fence_virt.conf

  libvirt

The libvirt plugin is the simplest plugin. It is used in environments where routing fencing requests between multiple hosts is not required, for example by a user running a cluster of virtual machines on a single desktop computer.

uri the URI to use when connecting to libvirt.

    All libvirt URIs are accepted and passed as-is.

    See https://libvirt.org/uri.html#remote-uris for examples.

    NOTE: When VMs are run as non-root user the socket path must be set as part of the URI.

    Example: qemu:///session?socket=/run/user/<UID>/libvirt/virtqemud-sock

  cpg

The cpg plugin uses corosync CPG and libvirt to track virtual machines and route fencing requests to the appropriate computer.

uri the URI to use when connecting to libvirt by the cpg plugin.

name_mode
    The cpg plugin, in order to retain compatibility with fence_xvm, stores virtual machines in a certain way. The default was to use 'name' when using fence_xvm and fence_xvmd, and so this is still the default. However, it is strongly recommended to use 'uuid' instead of 'name' in all cluster environments involving more than one physical host in order to avoid the potential for name collisions.

GROUPS

Fence_virtd supports static maps which allow grouping of VMs. The groups are arbitrary and are checked at fence time. Any member of a group may fence any other member. Hosts may be assigned to multiple groups if desired.

  group

This defines a group.

name
    Optionally define the name of the group. Useful only for configuration readability and debugging of configuration parsing.

uuid
    Defines UUID as a member of a group. It can be used multiple times to specify both node name and UUID values that can be fenced. When using the serial listener, the vm uuid is required and it is recommended to add also the vm name.

ip  Defines an IP which is allowed to send fencing requests for members of this group (e.g. for multicast). It can be used multiple times to allow more than 1 IP to send fencing requests to the group. It is highly recommended that this be used in conjunction with a key file. When using the vsock listener, ip should contain the CID value assigned by libvirt to the vm. When using the serial listener, ip value is not used and can be omitted.

EXAMPLE

 fence_virtd {
  listener = "multicast";
  backend = "cpg";
 }

 # this is the listeners section

 listeners {
  multicast {
   key_file = "/etc/cluster/fence_xvm.key";
  }
 }

 backends {
  libvirt {
   uri = "qemu:///system";
  }
 }

 groups {
  group {
   name = "cluster1";
   ip = "192.168.1.1";
   ip = "192.168.1.2";
   uuid = "44179d3f-6c63-474f-a212-20c8b4b25b16";
   uuid = "1ce02c4b-dfa1-42cb-b5b1-f0b1091ece60";
   uuid = "node1";
   uuid = "node2";
  }
 }

SEE ALSO
fence_virtd(8), fence_virt(8), fence_xvm(8), fence(8)