doc/topics/tutorials/cloud_controller.rst - master - githubmirror/salt

doc/topics/tutorials/cloud_controller.rst
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Daniel A. Wozniak
docs: refresh dead URLs in cloud, release notes and tutorial pages
28 июн 2026, 00:48
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.. _cloud-controller:

==========================
Salt as a Cloud Controller
==========================

In Salt 0.14.0, an advanced cloud control system was introduced, allowing
private cloud VMs to be managed directly with Salt. This system is generally
referred to as :strong:`Salt Virt`.

The Salt Virt system already exists and is installed within Salt itself. This
means that besides setting up Salt, no additional salt code needs to be
deployed.

.. note::

    The ``libvirt`` python module and the ``certtool`` binary are required.

The main goal of Salt Virt is to facilitate a very fast and simple cloud that
can scale and is fully featured. Salt Virt comes with the ability to set up and
manage complex virtual machine networking, powerful image and disk management,
and virtual machine migration with and without shared storage.

This means that Salt Virt can be used to create a cloud from a blade center
and a SAN, but can also create a cloud out of a swarm of Linux Desktops
without a single shared storage system. Salt Virt can make clouds from
truly commodity hardware, but can also stand up the power of specialized
hardware as well.

Setting up Hypervisors
======================

The first step to set up the hypervisors involves getting the correct software
installed and setting up the hypervisor network interfaces.

Installing Hypervisor Software
------------------------------

Salt Virt is made to be hypervisor agnostic but currently, the only fully
implemented hypervisor is KVM via libvirt.

The required software for a hypervisor is libvirt and kvm. For advanced
features, install libguestfs or qemu-nbd.

.. note::

    Libguestfs and qemu-nbd allow for virtual machine images to be mounted
    before startup and get pre-seeded with configurations and a salt minion.

This sls will set up the needed software for a hypervisor, and run the routines
to set up the libvirt pki keys.

.. note::

    Package names and setup used is Red Hat specific. Different package names
    will be required for different platforms.

.. code-block:: yaml

    libvirt:
      pkg.installed: []
      file.managed:
        - name: /etc/sysconfig/libvirtd
        - contents: 'LIBVIRTD_ARGS="--listen"'
        - require:
          - pkg: libvirt
      virt.keys:
        - require:
          - pkg: libvirt
      service.running:
        - name: libvirtd
        - require:
          - pkg: libvirt
          - network: br0
          - libvirt: libvirt
        - watch:
          - file: libvirt

    libvirt-python:
      pkg.installed: []

    libguestfs:
      pkg.installed:
        - pkgs:
          - libguestfs
          - libguestfs-tools

Hypervisor Network Setup
------------------------

The hypervisors will need to be running a network bridge to serve up network
devices for virtual machines. This formula will set up a standard bridge on
a hypervisor connecting the bridge to eth0:

.. code-block:: yaml

    eth0:
      network.managed:
        - enabled: True
        - type: eth
        - bridge: br0

    br0:
      network.managed:
        - enabled: True
        - type: bridge
        - proto: dhcp
        - require:
          - network: eth0


Virtual Machine Network Setup
-----------------------------

Salt Virt comes with a system to model the network interfaces used by the
deployed virtual machines. By default, a single interface is created for the
deployed virtual machine and is bridged to ``br0``. To get going with the
default networking setup, ensure that the bridge interface named ``br0`` exists
on the hypervisor and is bridged to an active network device.

.. note::

    To use more advanced networking in Salt Virt, read the `Salt Virt
    Networking` document:

    :ref:`Salt Virt Networking <vm-nic-profiles>`

Libvirt State
-------------

One of the challenges of deploying a libvirt based cloud is the distribution
of libvirt certificates. These certificates allow for virtual machine
migration. Salt comes with a system used to auto deploy these certificates.
Salt manages the signing authority key and generates keys for libvirt clients
on the master, signs them with the certificate authority, and uses pillar to
distribute them. This is managed via the ``libvirt`` state. Simply execute this
formula on the minion to ensure that the certificate is in place and up to
date:

.. note::

    The above formula includes the calls needed to set up libvirt keys.

.. code-block:: yaml

    libvirt_keys:
      virt.keys

Getting Virtual Machine Images Ready
====================================

Salt Virt requires that virtual machine images be provided as these are not
generated on the fly. Generating these virtual machine images differs greatly
based on the underlying platform.

Virtual machine images can be manually created using KVM and running through
the installer, but this process is not recommended since it is very manual and
prone to errors.

Virtual Machine generation applications are available for many platforms:

kiwi: (openSUSE, SLES, RHEL, CentOS)
  https://osinside.github.io/kiwi/

vm-builder:
  https://wiki.debian.org/VMBuilder

  .. seealso:: :formula_url:`vmbuilder-formula`

Once virtual machine images are available, the easiest way to make them
available to Salt Virt is to place them in the Salt file server. Just copy an
image into ``/srv/salt`` and it can now be used by Salt Virt.

For purposes of this demo, the file name ``centos.img`` will be used.

Existing Virtual Machine Images
-------------------------------

Many existing Linux distributions distribute virtual machine images which
can be used with Salt Virt. Please be advised that NONE OF THESE IMAGES ARE
SUPPORTED BY SALTSTACK.

CentOS
~~~~~~

These images have been prepared for OpenNebula but should work without issue with
Salt Virt, only the raw qcow image file is needed:
https://wiki.centos.org/Cloud/OpenNebula

Fedora Linux
~~~~~~~~~~~~

Images for Fedora Linux can be found here:
https://alt.fedoraproject.org/cloud

openSUSE
~~~~~~~~

https://download.opensuse.org/distribution/leap/15.1/jeos/openSUSE-Leap-15.1-JeOS.x86_64-15.1.0-kvm-and-xen-Current.qcow2.meta4

SUSE
~~~~

https://www.suse.com/products/server/jeos

Ubuntu Linux
~~~~~~~~~~~~

Images for Ubuntu Linux can be found here:
http://cloud-images.ubuntu.com/

Using Salt Virt
===============

With hypervisors set up and virtual machine images ready, Salt can start
issuing cloud commands using the `virt runner`.

Start by running a Salt Virt hypervisor info command:

.. code-block:: bash

    salt-run virt.host_info

This will query the running hypervisor(s) for stats and display useful
information such as the number of CPUs and amount of memory.

You can also list all VMs and their current states on all hypervisor nodes:

.. code-block:: bash

    salt-run virt.list

Now that hypervisors are available a virtual machine can be provisioned, the
``virt.init`` routine will create a new virtual machine:

.. code-block:: bash

    salt-run virt.init centos1 2 512 salt://centos.img

The Salt Virt runner will now automatically select a hypervisor to deploy
the new virtual machine on. Using ``salt://`` assumes that the CentOS virtual
machine image is located in the root of the :ref:`file-server` on the master.
When images are cloned (i.e. copied locally after retrieval from the file
server), the destination directory on the hypervisor minion is determined by the
``virt:images`` config option; by default this is ``/srv/salt-images/``.

When a VM is initialized using ``virt.init``, the image is copied to the
hypervisor using ``cp.cache_file`` and will be mounted and seeded with a minion.
Seeding includes setting pre-authenticated keys on the new machine. A minion
will only be installed if one can not be found on the image using the default
arguments to ``seed.apply``.

.. note::

    The biggest bottleneck in starting VMs is when the Salt Minion needs to be
    installed. Making sure that the source VM images already have Salt
    installed will GREATLY speed up virtual machine deployment.

You can also deploy an image on a particular minion by directly calling the
``virt`` execution module with an absolute image path. This can be quite handy for
testing:

.. code-block:: bash

    salt 'hypervisor*' virt.init centos1 2 512 image=/var/lib/libvirt/images/centos.img

Now that the new VM has been prepared, it can be seen via the ``virt.query``
command:

.. code-block:: bash

    salt-run virt.query

This command will return data about all of the hypervisors and respective
virtual machines.

Now that the new VM is booted, it should have contacted the Salt Master. A
``test.ping`` will reveal if the new VM is running.


QEMU Copy on Write Support
==========================

For fast image cloning, you can use the `qcow`_ disk image format.
Pass the ``enable_qcow`` flag and a `.qcow2` image path to `virt.init`:

.. code-block:: bash

    salt 'hypervisor*' virt.init centos1 2 512 image=/var/lib/libvirt/images/centos.qcow2 enable_qcow=True start=False

.. note::
    Beware that attempting to boot a qcow image too quickly after cloning
    can result in a race condition where libvirt may try to boot the machine
    before image seeding has completed. For that reason, it is recommended to
    also pass ``start=False`` to ``virt.init``.

    Also know that you **must not** modify the original base image without
    first making a copy and then *rebasing* all overlay images onto it.
    See the ``qemu-img rebase`` `usage docs <rebase>`_.

Migrating Virtual Machines
==========================

Salt Virt comes with full support for virtual machine migration. Using
the libvirt state in the above formula makes migration possible.

A few things need to be available to support migration. Many operating systems
turn on firewalls when originally set up; the firewall needs to be opened up
to allow for libvirt and kvm to cross communicate and execution migration
routines. On Red Hat based hypervisors in particular, port 16514 needs to be
opened on hypervisors:

.. code-block:: bash

    iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 16514 -j ACCEPT

.. note::

    More in-depth information regarding distribution specific firewall settings can be found in:

    :ref:`Opening the Firewall up for Salt <firewall>`

Salt also needs the ``virt:tunnel`` option to be turned on. This flag tells Salt
to run migrations securely via the libvirt TLS tunnel and to use port 16514.
Without ``virt:tunnel``, libvirt tries to bind to random ports when running
migrations.

To turn on ``virt:tunnel``, simply apply it to the master config file:

.. code-block:: yaml

    virt:
        tunnel: True

Once the master config has been updated, restart the master and send out a call
to the minions to refresh the pillar to pick up on the change:

.. code-block:: bash

    salt \* saltutil.refresh_modules

Now, migration routines can be run! To migrate a VM, simply run the Salt Virt
migrate routine:

.. code-block:: console

    salt-run virt.migrate centos <new hypervisor>

VNC Consoles
============

Although not enabled by default, Salt Virt can also set up VNC consoles allowing
for remote visual consoles to be opened up. When creating a new VM using
``virt.init``, pass the ``enable_vnc=True`` parameter to have a console
configured for the new VM.

The information from a ``virt.query`` routine will display the VNC console port
for the specific VMs:

.. code-block:: yaml

  centos
    CPU: 2
    Memory: 524288
    State: running
    Graphics: vnc - hyper6:5900
    Disk - vda:
      Size: 2.0G
      File: /srv/salt-images/ubuntu2/system.qcow2
      File Format: qcow2
    Nic - ac:de:48:98:08:77:
      Source: br0
      Type: bridge

The line `Graphics: vnc - hyper6:5900` holds the key. First the port named,
in this case 5900, will need to be available in the hypervisor's firewall.
Once the port is open, then the console can be easily opened via vncviewer:

.. code-block:: bash

    vncviewer hyper6:5900

By default there is no VNC security set up on these ports, which suggests that
keeping them firewalled and mandating that SSH tunnels be used to access these
VNC interfaces. Keep in mind that activity on a VNC interface that is accessed
can be viewed by any other user that accesses that same VNC interface, and any
other user logging in can also operate with the logged in user on the virtual
machine.

Conclusion
==========

Now with Salt Virt running, new hypervisors can be seamlessly added just by
running the above states on new bare metal machines, and these machines will be
instantly available to Salt Virt.

.. links
.. _qcow:
    https://en.wikipedia.org/wiki/Qcow
.. _rebase:
    https://docs.fedoraproject.org/en-US/Fedora/18/html/Virtualization_Administration_Guide/sect-Virtualization-Tips_and_tricks-Using_qemu_img.html