============================
Getting Started With Libvirt
============================

Libvirt is a toolkit to interact with the virtualization capabilities of recent versions
of Linux (and other OSes). This driver Salt cloud provider is currently geared towards
libvirt with qemu-kvm.

http://www.libvirt.org/

Host Dependencies
=================
* libvirt >= 1.2.18 (older might work)

Salt-Cloud Dependencies
=======================
* libvirt-python

Provider Configuration
======================

For every KVM host a provider needs to be set up. The provider currently maps to one libvirt daemon (e.g. one KVM host).

Set up the provider cloud configuration file at ``/etc/salt/cloud.providers`` or
``/etc/salt/cloud.providers.d/*.conf``.


.. code-block:: yaml

    # Set up a provider with qemu+ssh protocol
    kvm-via-ssh:
      driver: libvirt
      url: qemu+ssh://user@kvm.company.com/system?socket=/var/run/libvirt/libvirt-sock

    # Or connect to a local libvirt instance
    local-kvm:
      driver: libvirt
      url: qemu:///system
      # work around flag for XML validation errors while cloning
      validate_xml: no

Cloud Profiles
==============
Virtual machines get cloned from so called Cloud Profiles. Profiles can be set up at ``/etc/salt/cloud.profiles`` or
``/etc/salt/cloud.profiles.d/*.conf``:

* Configure a profile to be used:

.. code-block:: yaml

    centos7:
      # points back at provider configuration
      provider: local-kvm
      base_domain: base-centos7-64
      ip_source: ip-learning
      ssh_username: root
      password: my-very-secret-password
      # /tmp is mounted noexec.. do workaround
      deploy_command: sh /tmp/.saltcloud/deploy.sh
      script_args: -F
      # grains to add to the minion
      grains:
        clones-are-awesome: true
      # override minion settings
      minion:
        master: 192.168.16.1
        master_port: 5506


The profile can be realized now with a salt command:

.. code-block:: bash

    # salt-cloud -p centos7 my-centos7-clone

This will create an instance named ``my-centos7-clone`` on the cloud host. Also
the minion id will be set to ``my-centos7-clone``.

If the command was executed on the salt-master, its Salt key will automatically
be signed on the master.

Once the instance has been created with salt-minion installed, connectivity to
it can be verified with Salt:

.. code-block:: bash

    # salt my-centos7-clone test.version


Required Settings
=================
The following settings are always required for libvirt:

.. code-block:: yaml

    centos7:
      provider: local-kvm
      # the domain to clone
      base_domain: base-centos7-64
      # how to obtain the IP address of the cloned instance
      # ip-learning or qemu-agent
      ip_source: ip-learning

The ``ip_source`` setting controls how the IP address of the cloned instance is determined.
When using ``ip-learning`` the IP is requested from libvirt. This needs a recent libvirt
version and may only work for NAT networks. Another option is to use ``qemu-agent`` this requires
that the qemu-agent is installed and configured to run at startup in the base domain.

Optional Settings
=================

.. code-block:: yaml

    # Username and password
    ssh_username: root
    password: my-secret-password

    # Cloning strategy: full or quick
    clone_strategy: quick

The ``clone_strategy`` controls how the clone is done. In case of ``full`` the disks
are copied creating a standalone clone. If ``quick`` is used the disks of the base domain
are used as backing disks for the clone. This results in nearly instantaneous clones at
the expense of slower write performance. The quick strategy has a number of requirements:

* The disks must be of type qcow2
* The base domain must be turned off
* The base domain must not change after creating the clone
