Synnefo

.. _admin-guide:

Synnefo Administrator's Guide

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is the complete Synnefo Administrator's Guide.

.. _syn+archip:

General Synnefo Architecture

============================

The following figure shows a detailed view of the whole Synnefo architecture

and how it interacts with multiple Ganeti clusters. We hope that after reading

the Administrator's Guide you will be able to understand every component and

all the interactions between them.

.. image:: images/synnefo-arch2.png

   :width: 100%

   :target: _images/synnefo-arch2.png

Synnefo also supports RADOS as an alternative storage backend for

Files/Images/VM disks. You will find the :ref:`corresponding figure

<syn+archip+rados>` later in this guide.

Identity Service (Astakos)

==========================

Authentication methods

----------------------

Astakos supports multiple authentication methods:

 * local username/password

 * LDAP / Active Directory

 * SAML 2.0 (Shibboleth) federated logins

 * Google

 * Twitter

 * LinkedIn

.. _shibboleth-auth:

Shibboleth Authentication

~~~~~~~~~~~~~~~~~~~~~~~~~

Astakos can delegate user authentication to a Shibboleth federation.

To setup shibboleth, install package::

  apt-get install libapache2-mod-shib2

Change appropriately the configuration files in ``/etc/shibboleth``.

Add in ``/etc/apache2/sites-available/synnefo-ssl``::

  ShibConfig /etc/shibboleth/shibboleth2.xml

  Alias      /shibboleth-sp /usr/share/shibboleth

  <Location /ui/login/shibboleth>

    AuthType shibboleth

    ShibRequireSession On

    ShibUseHeaders On

    require valid-user

  </Location>

and before the line containing::

  ProxyPass        / http://localhost:8080/ retry=0

add::

  ProxyPass /Shibboleth.sso !

Then, enable the shibboleth module::

  a2enmod shib2

After passing through the apache module, the following tokens should be

available at the destination::

  eppn # eduPersonPrincipalName

  Shib-InetOrgPerson-givenName

  Shib-Person-surname

  Shib-Person-commonName

  Shib-InetOrgPerson-displayName

  Shib-EP-Affiliation

  Shib-Session-ID

Astakos keeps a map of shibboleth users using the value of the ``REMOTE_USER``

header, passed by the ``mod_shib2`` module. This happens in order to be able to

identify the astakos account the shibboleth user is associated to, every time

the user logs in from an affiliate shibboleth IdP. 

The shibboleth attribute which gets mapped to the ``REMOTE_USER`` header can be

changed in ``/etc/shibboleth/shibboleth2.xml`` configuration file.

.. code-block:: xml

    <!-- The ApplicationDefaults element is where most of Shibboleth's SAML bits are defined. -->

        <ApplicationDefaults entityID="https://sp.example.org/shibboleth" 

         REMOTE_USER="eppn persistent-id targeted-id">

.. warning::

 Changing ``mod_shib2`` ``REMOTE_USER`` to map to different shibboleth

 attributes will probably invalidate any existing shibboleth enabled users in

 astakos database. Those users won't be able to login to their existing accounts.

Finally, add 'shibboleth' in ``ASTAKOS_IM_MODULES`` list. The variable resides

inside the file ``/etc/synnefo/20-snf-astakos-app-settings.conf``

Twitter Authentication

~~~~~~~~~~~~~~~~~~~~~~

To enable twitter authentication while signed in under a Twitter account,

visit dev.twitter.com/apps.

Click Create an application.

Fill the necessary information and for callback URL give::

    https://node1.example.com/ui/login/twitter/authenticated

Finally, add 'twitter' in ``ASTAKOS_IM_MODULES`` list. The variable resides

inside the file ``/etc/synnefo/20-snf-astakos-app-settings.conf``

Google Authentication

~~~~~~~~~~~~~~~~~~~~~

To enable google authentication while signed in under a Google account,

visit https://code.google.com/apis/console/.

Under API Access select Create another client ID, select Web application,

expand more options in Your site or hostname section and in Authorized

Redirect URIs add:

Fill the necessary information and for callback URL give::

    https://node1.example.com/ui/login/google/authenticated

Finally, add 'google' in ``ASTAKOS_IM_MODULES`` list. The variable resides

inside the file ``/etc/synnefo/20-snf-astakos-app-settings.conf``

Working with Astakos

--------------------

User registration

~~~~~~~~~~~~~~~~~

When a new user signs up, he/she is not directly marked as active. You can see

his/her state by running (on the machine that runs the Astakos app):

.. code-block:: console

   $ snf-manage user-list

More detailed user status is provided in the `status` field of the `user-show`

command:

.. code-block:: console

  $ snf-manage user-show <user-id>

  id                  : 6

  uuid                : 78661411-5eed-412f-a9ea-2de24f542c2e

  status              : Accepted/Active (accepted policy: manual)

  email               : user@synnefo.org

  ....

Based on the `astakos-app` configuration, there are several ways for a user to

get verified and activated in order to be able to login. We discuss the user

verification and activation flow in the following section.

User activation flow

````````````````````

A user can register for an account using the astakos signup form. Once the form

is submited successfully a user entry is created in astakos database. That entry

is passed through the astakos activation backend which handles whether the user

should be automatically verified and activated.

Email verification

``````````````````

The verification process takes place in order to ensure that the user owns the

email provided during the signup process. By default, after each successful

signup astakos notifies user with an verification url via email.

At this stage:

    * subsequent registrations invalidate and delete the previous registrations

      of the same email address.

    * in case user misses the initial notification, additional emails can be

      send either via the url which is prompted to the user if he tries to

      login, or by the administrator using the ``snf-manage user-activation-send

      <userid>`` command.

    * administrator may also enforce a user to get verified using the

      ``snf-manage user-modify --verify <userid>`` command.

Account activation

``````````````````

Once the user gets verified, it is time for Astakos to decide whether or not to

proceed through user activation process. If ``ASTAKOS_MODERATION_ENABLED``

setting is set to ``False`` (default value) user gets activated automatically.

In case the moderation is enabled Astakos may still automatically activate the

user in the following cases:

    * User email matches any of the regular expressions defined in

      ``ASTAKOS_RE_USER_EMAIL_PATTERNS`` (defaults to ``[]``)

    * User used a signup method (e.g. ``shibboleth``) for which automatic

      activation is enabled (see

      :ref:`authentication methods policies <auth_methods_policies>`).

If all of the above fail to trigger automatic activation, an email is sent to

the persons listed in ``HELPDESK``, ``MANAGERS`` and ``ADMINS`` settings,

notifing that there is a new user pending for moderation and that it's up to

the administrator to decide if the user should be activated. The UI also shows

a corresponding 'pending moderation' message to the user. The administrator can

activate a user using the ``snf-manage user-modify`` command:

.. code-block:: console

    # command to activate a pending user

    $ snf-manage user-modify --accept <userid>

    # command to reject a pending user

    $ snf-manage user-modify --reject --reject-reason="spammer" <userid>

Once the activation process finishes, a greeting message is sent to the user

email address and a notification for the activation to the persons listed in

``HELPDESK``, ``MANAGERS`` and ``ADMINS`` settings. Once activated the user is

able to login and access the Synnefo services.

Additional authentication methods

`````````````````````````````````

Astakos supports third party logins from external identity providers. This

can be usefull since it allows users to use their existing credentials to

login to astakos service.

Currently astakos supports the following identity providers:

    * `Shibboleth <http://www.internet2.edu/shibboleth>`_ (module name

      ``shibboleth``)

    * `Google <https://developers.google.com/accounts/docs/OAuth2>`_ (module

      name ``google``)

    * `Twitter <https://dev.twitter.com/docs/auth>`_ (module name ``twitter``)

    * `LinkedIn <http://developer.linkedin.com/documents/authentication>`_

      (module name ``linkedin``)

To enable any of the above modules (by default only ``local`` accounts are

allowed), retrieve and set the required provider settings and append the

module name in ``ASTAKOS_IM_MODULES``.

.. code-block:: python

    # settings from https://code.google.com/apis/console/

    ASTAKOS_GOOGLE_CLIENT_ID = '1111111111-epi60tvimgha63qqnjo40cljkojcann3.apps.googleusercontent.com'

    ASTAKOS_GOOGLE_SECRET = 'tNDQqTDKlTf7_LaeUcWTWwZM'

    # let users signup and login using their google account

    ASTAKOS_IM_MODULES = ['local', 'google']

.. _auth_methods_policies:

Authentication method policies

``````````````````````````````

Astakos allows you to override the default policies for each enabled provider

separately by adding the approriate settings in your ``.conf`` files in the

following format:

**ASTAKOS_AUTH_PROVIDER_<module>_<policy>_POLICY**

Available policies are:

    * **CREATE** Users can signup using that provider (default: ``True``)

    * **REMOVE/ADD** Users can remove/add login method from their profile

      (default: ``True``)

    * **AUTOMODERATE** Automatically activate users that signup using that

      provider (default: ``False``)

    * **LOGIN** Whether or not users can use the provider to login (default:

      ``True``).

e.g. to enable automatic activation for your academic users, while keeping

locally signed up users under moderation you can apply the following settings.

.. code-block:: python

    ASTAKOS_AUTH_PROVIDER_SHIBBOLETH_AUTOMODERATE_POLICY = True

    ASTAKOS_AUTH_PROVIDER_SHIBBOLETH_REMOVE_POLICY = False

User login

~~~~~~~~~~

During the logging procedure, the user is authenticated by the respective

identity provider.

If ``ASTAKOS_RECAPTCHA_ENABLED`` is set and the user fails several times

(``ASTAKOS_RATELIMIT_RETRIES_ALLOWED`` setting) to provide the correct

credentials for a local account, he/she is then prompted to solve a captcha

challenge.

Upon success, the system renews the token (if it has expired), logins the user

and sets the cookie, before redirecting the user to the ``next`` parameter

value.

Setting quota limits

~~~~~~~~~~~~~~~~~~~~

Set default quota

`````````````````

To inspect current default base quota limits, run::

   # snf-manage resource-list

You can modify the default base quota limit for all future users with::

   # snf-manage resource-modify <resource_name> --default-quota <value>

Set base quota for individual users

```````````````````````````````````

For individual users that need different quota than the default

you can set it for each resource like this::

    # use this to display quota / uuid

    # snf-manage user-show 'uuid or email' --quota

    # snf-manage user-modify <user-uuid> --base-quota 'cyclades.vm' 10

You can set base quota for all existing users, with possible exceptions, using::

    # snf-manage user-modify --all --base-quota cyclades.vm 10 --exclude uuid1,uuid2

All quota for which values different from the default have been set,

can be listed with::

    # snf-manage quota-list --with-custom=True

Enable the Projects feature

~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you want to enable the projects feature so that users may apply

on their own for resources by creating and joining projects,

in ``20-snf-astakos-app-settings.conf`` set::

    # this will make the 'projects' page visible in the dashboard

    ASTAKOS_PROJECTS_VISIBLE = True

You can change the maximum allowed number of pending project applications

per user with::

    # snf-manage resource-modify astakos.pending_app --default-quota <number>

You can also set a user-specific limit with::

    # snf-manage user-modify <user-uuid> --base-quota 'astakos.pending_app' 5

When users apply for projects they are not automatically granted

the resources. They must first be approved by the administrator.

To list pending project applications in astakos::

    # snf-manage project-list --pending

Note the last column, the application id. To approve it::

    # <app id> from the last column of project-list

    # snf-manage project-control --approve <app id>

To deny an application::

    # snf-manage project-control --deny <app id>

Users designated as *project admins* can approve, deny, or modify

an application through the web interface. In

``20-snf-astakos-app-settings.conf`` set::

    # UUIDs of users that can approve or deny project applications from the web.

    ASTAKOS_PROJECT_ADMINS = [<uuid>, ...]

Astakos advanced operations

---------------------------

Adding "Terms of Use"

~~~~~~~~~~~~~~~~~~~~~

Astakos supports versioned terms-of-use. First of all you need to create an

html file that will contain your terms. For example, create the file

``/usr/share/synnefo/sample-terms.html``, which contains the following:

.. code-block:: console

   <h1>My cloud service terms</h1>

   These are the example terms for my cloud service

Then, add those terms-of-use with the snf-manage command:

.. code-block:: console

   $ snf-manage term-add /usr/share/synnefo/sample-terms.html

Your terms have been successfully added and you will see the corresponding link

appearing in the Astakos web pages' footer.

During the account registration, if there are approval terms, the user is

presented with an "I agree with the Terms" checkbox that needs to get checked

in order to proceed.

In case there are new approval terms that the user has not signed yet, the

``signed_terms_required`` view decorator redirects to the ``approval_terms``

view, so the user will be presented with the new terms the next time he/she

logins.

Enabling reCAPTCHA

~~~~~~~~~~~~~~~~~~

Astakos supports the `reCAPTCHA <http://www.google.com/recaptcha>`_ feature.

If enabled, it protects the Astakos forms from bots. To enable the feature, go

to https://www.google.com/recaptcha/admin/create and create your own reCAPTCHA

key pair. Then edit ``/etc/synnefo/20-snf-astakos-app-settings.conf`` and set

the corresponding variables to reflect your newly created key pair. Finally, set

the ``ASTAKOS_RECAPTCHA_ENABLED`` variable to ``True``:

.. code-block:: console

   ASTAKOS_RECAPTCHA_PUBLIC_KEY = 'example_recaptcha_public_key!@#$%^&*('

   ASTAKOS_RECAPTCHA_PRIVATE_KEY = 'example_recaptcha_private_key!@#$%^&*('

   ASTAKOS_RECAPTCHA_ENABLED = True

Restart the service on the Astakos node(s) and you are ready:

.. code-block:: console

   # /etc/init.d/gunicorn restart

Checkout your new Sign up page. If you see the reCAPTCHA box, you have setup

everything correctly.

Astakos internals

-----------------

X-Auth-Token

~~~~~~~~~~~~

Alice requests a specific resource from a cloud service e.g.: Pithos. In the

request she supplies the `X-Auth-Token` to identify whether she is eligible to

perform the specific task. The service contacts Astakos through its

``/account/v1.0/authenticate`` api call (see :ref:`authenticate-api-label`)

providing the specific ``X-Auth-Token``. Astakos checkes whether the token

belongs to an active user and it has not expired and returns a dictionary

containing user related information. Finally the service uses the ``uniq``

field included in the dictionary as the account string to identify the user

accessible resources.

.. _authentication-label:

Django Auth methods and Backends

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Astakos incorporates Django user authentication system and extends its User model.

Since username field of django User model has a limitation of 30 characters,

AstakosUser is **uniquely** identified by the ``email`` instead. Therefore,

``astakos.im.authentication_backends.EmailBackend`` is served to authenticate a

user using email if the first argument is actually an email, otherwise tries

the username.

A new AstakosUser instance is assigned with a uui as username and also with a

``auth_token`` used by the cloud services to authenticate the user.

``astakos.im.authentication_backends.TokenBackend`` is also specified in order

to authenticate the user using the email and the token fields.

Logged on users can perform a number of actions:

 * access and edit their profile via: ``/im/profile``.

 * change their password via: ``/im/password``

 * send feedback for grnet services via: ``/im/send_feedback``

 * logout (and delete cookie) via: ``/im/logout``

Internal Astakos requests are handled using cookie-based Django user sessions.

External systems should forward to the ``/login`` URI. The server,

depending on its configuration will redirect to the appropriate login page.

When done with logging in, the service's login URI should redirect to the URI

provided with next, adding user and token parameters, which contain the email

and token fields respectively.

The login URI accepts the following parameters:

======================  =========================

Request Parameter Name  Value

======================  =========================

next                    The URI to redirect to when the process is finished

renew                   Force token renewal (no value parameter)

force                   Force logout current user (no value parameter)

======================  =========================

External systems inside the ``ASTAKOS_COOKIE_DOMAIN`` scope can acquire the

user information by the cookie identified by ``ASTAKOS_COOKIE_NAME`` setting

(set during the login procedure).

Finally, backend systems having acquired a token can use the

:ref:`authenticate-api-label` API call from a private network or through HTTPS.

Compute/Network/Image Service (Cyclades)

========================================

Introduction

------------

Cyclades is the Synnefo component that implements Compute, Network and Image

services and exposes the associated OpenStack REST APIs. By running Cyclades

you can provide a cloud that can handle thousands of virtual servers and

networks.

Cyclades does not include any virtualization software and knows nothing about

the low-level VM management operations, e.g. handling of VM creation or

migrations among physical nodes. Instead, Cyclades is the component that

handles multiple Ganeti backends and exposes the REST APIs. The administrator

can expand the infrastructure dynamically either by adding more Ganeti nodes

or by adding new Ganeti clusters. Cyclades issue VM control commands to Ganeti

via Ganeti's remote API and receive asynchronous notifications from Ganeti

backends whenever the state of a VM changes, due to Synnefo- or

administrator-initiated commands.

Cyclades is the action orchestrator and the API layer on top of multiple Ganeti

clusters. By this decoupled design, Ganeti cluster are self-contained and

the administrator has complete control on them without Cyclades knowing about

it. For example a VM migration to a different physical node is transparent

to Cyclades.

Working with Cyclades

---------------------

Flavors

~~~~~~~

When creating a VM, the user must specify the `flavor` of the virtual server.

Flavors are the virtual hardware templates, and provide a description about

the number of CPUs, the amount of RAM, and the size of the disk of the VM.

Besides the size of the disk, Cyclades flavors describe the storage backend

that will be used for the virtual server.

Flavors are created by the administrator and the user can select one of the

available flavors. After VM creation, the user can resize his VM, by

adding/removing CPU and RAM.

Cyclades support different storage backends that are described by the disk

template of the flavor, which is mapped to Ganeti's instance `disk template`.

Currently the available disk templates are the following:

* `file`: regulars file

* `sharedfile`: regular files on a shared directory, e.g. NFS

* `plain`: logical volumes

* `drbd`: drbd on top of lvm volumes

* `rbd`: rbd volumes residing inside a RADOS cluster

* `ext`: disks provided by an external shared storage.

  - `ext_archipelago`: External shared storage provided by

    `Archipelago <http://www.synnefo.org/docs/archipelago/latest/index.html>`_.

Flavors are created by the administrator using `snf-manage flavor-create`

command. The command takes as argument number of CPUs, amount of RAM, the size

of the disks and the disk templates and create the flavors that belong to the

cartesian product of the specified arguments. For example, the following

command will create two flavors of `40G` disk size with `drbd` disk template,

`4G` RAM and `2` or `4` CPUs.

.. code-block:: console

  $ snf-manage flavor-create 2,4 4096 40 drbd

To see the available flavors, run `snf-manage flavor-list` command. Finally,

the administrator can delete a flavor by using `flavor-modify` command:

.. code-block:: console

  $ snf-manage flavor-modify --deleted=True <flavor_id>

Images

~~~~~~

When creating a VM the user must also specify the `image` of the virtual

server. Images are the static templates from which VM instances are

initiated. Cyclades uses Pithos to store system and user-provided images,

taking advantage of all Pithos features, like deduplication and syncing

protocol. An image is a file stored to Pithos with additional metadata that

are describing the image, e.g. the OS family or the root partition. To create

a new image, the administrator or the user has to upload it a file to Pithos,

and then register it as an Image with Cyclades. Then the user can use this

image to spawn new VMs from it.

Images can be private, public or shared between users, exactly like Pithos

files. Since user-provided public images can be untrusted, the administrator

can denote which users are trusted by adding them to the

``UI_SYSTEM_IMAGES_OWNERS`` setting in the

`/etc/synnefo/20-snf-cyclades-app-ui.conf` file. Images of those users are

properly displayed in the UI.

When creating a new VM, Cyclades pass the location of the image and it's

metadata to Ganeti. After Ganeti creates the instance's disk, `snf-image`

will copy the image to the new disk and perform the image customization

phase. During the phase, `snf-image` sends notifications to Cyclades about

the progress of the image deployment and customization. Customization includes

resizing the root file system, file injection (e.g. SSH keys) and setting

a custom hostname. For better understanding of `snf-image` read the

corresponding `documentation

<http://www.synnefo.org/docs/snf-image/latest/index.html>`_.

For passing sensitive data about the image to Ganeti, like the VMs password,

Cyclades keeps all sensitive data in memory caches (memcache) and never allows

them to hit the disk. The data are exposed to `snf-image` via an one-time URL

that is exposed from the `vmapi` application. So, instead of passing sensitive

data to `snf-image` via Ganeti, Cyclades pass an one-time configuration URL

that contains a random UUID. After `snf-image` gets the sensitive data, the

URL is invalidated so no one else can access them.

The administrator can register images, exactly like users, using a system user

(a user that is defined in the ``UI_SYSTEM_IMAGES_OWNERS`` setting). For

example, the following command will register the

`pithos://u53r-un1qu3-1d/images/debian_base-6.0-7-x86_64.diskdump` as an

image to Cyclades:

.. code-block:: console

 $ kamaki image register "Debian Base" \

        pithos://u53r-un1qu3-1d/images/debian_base-6.0-7-x86_64.diskdump \

        --public \

        --disk-format=diskdump \

        --property OSFAMILY=linux --property ROOT_PARTITION=1 \

        --property description="Debian Squeeze Base System" \

        --property size=451 --property kernel=2.6.32 --property GUI="No GUI" \

        --property sortorder=1 --property USERS=root --property OS=debian

Deletion of an image is done via `kamaki image unregister` command, which will

delete the Cyclades Images but will leave the Pithos file as is (unregister).

Apart from using `kamaki` to see and hangle the available images, the

administrator can use `snf-manage image-list` and `snf-manage image-show`

commands to list and inspect the available public images. Also, the `--user-id`

option can be used the see the images of a specific user.

Virtual Servers

~~~~~~~~~~~~~~~

As mentioned, Cyclades uses Ganeti for management of VMs. The administrator can

handle Cyclades VMs just like any other Ganeti instance, via `gnt-instance`

commands. All Ganeti instances that belong to Synnefo, are separated from

others, by a prefix in their names. This prefix is defined in

``BACKEND_PREFIX_ID`` setting in

``/etc/synnefo/20-snf-cyclades-app-backend.conf``.

Apart from handling Cyclades VM at the Ganeti level, the administrator can

also use the `snf-manage server-*` commands. These command cover the most

common tasks that are relative with VM handling. Below we describe come

of them, but for more information you can use the `--help` option of all

`snf-manage server-* commands`. These command cover the most

The `snf-manage server-create` command can be used to create a new VM for some

user. This command can be useful when the administrator wants to test Cyclades

functionality without starting the API service, e.g. after an upgrade. Also, by

using `--backend-id` option, the VM will be created in the specified backend,

bypassing automatic VM allocation.

.. code-block:: console

 $ snf-manage server-create --flavor-id=1 --image-id=fc0f6858-f962-42ce-bf9a-1345f89b3d5e \

    --user-id=7cf4d078-67bf-424d-8ff2-8669eb4841ea --backend-id=2 \

    --password='example_passw0rd' --name='test_vm'

The above commnd will create a new VM for user

`7cf4d078-67bf-424d-8ff2-8669eb4841ea` in the Ganeti backend with ID 2. By

default this command will issue a Ganeti job to create the VM

(`OP_INSTANCE_CREATE`) and return. As in other commands, the `--wait=True`

option can be used in order to wait for the successful completion of the job.

`snf-manage server-list` command can be used to list all the available servers.

The command supports some useful options, like listing servers of a user,

listing servers that exist in a Ganeti backend and listing deleted servers.

Also, as in most of `*-list` commands, the `--filter-by` option can be used to

filter the results. For example, the following command will only display the

started servers of a specific flavor:

.. code-block:: console

 $ snf-manage server-list --filter-by="operstate=STARTED,flavor=<flavor_id>"

Another very useful command is the `server-inspect` command which will display

all available information about the state of the server in DB and the state

of the server in the Ganeti backend. The output will give you an easy overview

about the state of the VM which can be useful for debugging.

Also the administrator can `suspend` a user's VM, using the `server-modify`

command:

.. code-block:: console

 $ snf-manage server-modify --suspended=True <server_id>

The user is forbidden to do any action on an administratively suspended VM,

which is useful for abuse cases.

Ganeti backends

~~~~~~~~~~~~~~~

Since v0.11, Synnefo is able to manage multiple Ganeti clusters (backends)

making it capable to scale linearly to tens of thousands of VMs. Backends

can be dynamically added or removed via `snf-manage` commands.

Each newly created VM is allocated to a Ganeti backend by the Cyclades backend

allocator. The VM is "pinned" to this backend, and can not change through its

lifetime. The backend allocator decides in which backend to spawn the VM based

on the available resources of each backend, trying to balance the load between

them. Also, Networks are created to all Ganeti backends, in order to ensure

that VMs residing on different backends can be connected to the same networks.

A backend can be marked as `drained` in order to be excluded from automatic

servers allocation and not receive new servers. Also, a backend can be marked

as `offline` to denote that the backend is not healthy (e.g. broken master)

and avoid the penalty of connection timeouts.

Finally, Cyclades is able to manage Ganeti backends with different enabled

hypervisors (`kvm`, `xen`), and different enabled disk templates.

Listing existing backends

`````````````````````````

To list all the Ganeti backends known to Synnefo, we run:

.. code-block:: console

   $ snf-manage backend-list

Adding a new Ganeti backend

```````````````````````````

Backends are dynamically added under the control of Synnefo with `snf-manage

backend-add` command. In this section it is assumed that a Ganeti cluster,

named ``cluster.example.com`` is already up and running and configured to be

able to host Synnefo VMs.

To add this Ganeti cluster, we run:

.. code-block:: console

   $ snf-manage backend-add --clustername=cluster.example.com --user="synnefo_user" --pass="synnefo_pass"

where ``clustername`` is the Cluster hostname of the Ganeti cluster, and

``user`` and ``pass`` are the credentials for the `Ganeti RAPI user

<http://docs.ganeti.org/ganeti/2.2/html/rapi.html#users-and-passwords>`_.  All

backend attributes can be also changed dynamically using the `snf-manage

backend-modify` command.

``snf-manage backend-add`` will also create all existing public networks to

the new backend. You can verify that the backend is added, by running

`snf-manage backend-list`.

Note that no VMs will be spawned to this backend, since by default it is in a

``drained`` state after addition in order to manually verify the state of the

backend.

So, after making sure everything works as expected, make the new backend active

by un-setting the ``drained`` flag. You can do this by running:

.. code-block:: console

   $ snf-manage backend-modify --drained=False <backend_id>

Allocation of VMs in Ganeti backends

````````````````````````````````````

As already mentioned, the Cyclades backend allocator is responsible for

allocating new VMs to backends. This allocator does not choose the exact Ganeti

node that will host the VM but just the Ganeti backend. The exact node is

chosen by the Ganeti cluster's allocator (hail).

The decision about which backend will host a VM is based on the available

resources. The allocator computes a score for each backend, that shows its load

factor, and the one with the minimum score is chosen. The admin can exclude

backends from the allocation phase by marking them as ``drained`` by running:

.. code-block:: console

   $ snf-manage backend-modify --drained=True <backend_id>

The backend resources are periodically updated, at a period defined by

the ``BACKEND_REFRESH_MIN`` setting, or by running `snf-manage

backend-update-status` command. It is advised to have a cron job running this

command at a smaller interval than ``BACKEND_REFRESH_MIN`` in order to remove

the load of refreshing the backends stats from the VM creation phase.

Finally, the admin can decide to have a user's VMs being allocated to a

specific backend, with the ``BACKEND_PER_USER`` setting. This is a mapping

between users and backends. If the user is found in ``BACKEND_PER_USER``, then

Synnefo allocates all his/hers VMs to the specific backend in the variable,

even if is marked as drained (useful for testing).

Allocation based on disk-templates

**********************************

Besides the available resources of each Ganeti backend, the allocator takes

into consideration the disk template of the instance when trying to allocate it

to a Ganeti backend. Specifically, the allocator checks if the flavor of the

instance belongs to the available disk templates of each Ganeti backend.

A Ganeti cluster has a list of enabled disk templates

(`--enabled-disk-templates`) and a list of allowed disk templates for new

instances (`--ipolicy-disk-templates`). See the `gnt-cluster` manpage for more

details about these options.

When Synnefo allocates an instance, it checks whether the disk template of the

new instance belongs both in the enabled and ipolicy disk templates. You can

see the list of the available disk-templates by running `snf-manage

backend-list`. This list should be updated automatically after changing

these options in Ganeti and it can also be updated by running `snf-manage

backend-update-status`.

So the administrator, can route instances on different backends based on their

flavor disk template, by modifying the enabled or ipolicy disk templates of

each backend.  Also, the administrator can route instances between different

nodes of the same Ganeti backend, by modifying the same options at the

nodegroup level (see `gnt-group` manpage for mor details).

Removing an existing Ganeti backend

```````````````````````````````````

In order to remove an existing backend from Synnefo, you must first make

sure that there are not active servers in the backend, and then run:

.. code-block:: console

   $ snf-manage backend-remove <backend_id>

Virtual Networks

~~~~~~~~~~~~~~~~

Cyclades also implements the Network service and exposes the Quantum Openstack

API. Cyclades supports full IPv4 and IPv6 connectivity to the public internet

for it's VMs. Also, Cyclades provides L2 and L3 virtual private networks,

giving the user freedom to create arbitraty network topologies of

interconnected VMs.

Public networking is desployment specific and must be customized based on the

specific needs of the system administrator. Private virtual networks can be

provided by different network technologies which are exposed as different

network flavors. For better understanding of networking please refer to the

:ref:`Network <networks>` section.

A Cyclades virtual network is an isolated Layer-2 broadcast domain. A network

can also have an associated IPv4 and IPv6 subnet representing the Layer-3

characteristics of the network. Each subnet represents an IP address block

that is used in order to assign addresses to VMs.

To connect a VM to a network, a port must be created, which represent a virtual

port on a network switch. VMs are connected to networks by attaching a virtual

interface to a port.

Cyclades also supports `floating IPs`, which are public IPv4 addresses that

can dynamically(hotplug-able) be added and removed to VMs. Floating IPs are

a quotable resource that is allocated to each user. Unlike other cloud

platforms, floating IPs are not implemented using 1-1 NAT to a ports private

IP. Instead, floating IPs are directly assigned to virtual interfaces of VMs.

Exactly like VMS, networks can be handled as Ganeti networks via `gnt-network`

commands. All Ganeti networks that belong to Synnefo are named with the prefix

`${BACKEND_PREFIX_ID}-net-`. Also, there are a number of `snf-manage` commands

for handling of `networks`, `subnets`, `ports` and `floating IPs`. Below

we will present a use case scenario using some of these commands. For better

understanding of these commands, refer to their help messages.

Create a virtual private network for user

`7cf4d078-67bf-424d-8ff2-8669eb4841ea` using the `PHYSICAL_VLAN` flavor, which

means that the network will be uniquely assigned a phsyical VLAN. The network

is assigned an IPv4 subnet, described by it's CIDR and gateway. Also,

the `--dhcp=True` option is used, to make `nfdhcpd` response to DHCP queries

from VMs.

.. code-block:: console

 $ snf-manage network-create --owner=7cf4d078-67bf-424d-8ff2-8669eb4841ea --name=prv_net-1 \

    --subnet=192.168.2.0/24 --gateway=192.168.2.1 --dhcp=True --flavor=PHYSICAL_VLAN

Inspect the state of the network in Cyclades DB and in all the Ganeti backends:

.. code-block:: console

  $ snf-manage network-inspect <network_id>

Inspect the state of the network's subnet, containg an overview of the

subnet's IPv4 address allocation pool:

.. code-block:: console

  $ snf-manage subnet-inspect <subnet_id>

Connect a VM to the created private network. The port will be automatically

be assigned an IPv4 address from one of the network's available IPs. This

command will result in sending an `OP_INSTANCE_MODIFY` Ganeti command and

attaching a NIC to the specified Ganeti instance.

.. code-block:: console

 $ snf-manage port-create --network=<network_id> --server=<server_id>

Inspect the state of the the port in Cyclades DB and in the Ganeti backend:

.. code-block:: console

 $ snf-manage port-inspect <port_id>

Disconnect the VM from the network and delete the network:

.. code-block:: console

 $ snf-manage port-remove <port_id>

 $ snf-manage network-remove <network_id>

Enabling DHCP

`````````````

When connecting a VM to a network, Cyclades will automatically assign an IPv4

address from the IPv4 or/and IPv6 subnets of the network. If the network has

no subnets, then it will not be assigned any IP address.

If the network has DHCP enabled, then `nfdhcpd` daemon, which must be running

on all Ganeti nodes, will respond to DHCP queries from VMs and assign to them

the IP address that was allocated by Cyclades. DCHP can be enabled/disabled

using the `--dhcp` option of `network-create` command.

Public network connectivity

```````````````````````````

Since v0.14, users are able to dynamically connect and disconnect their VMs

from public networks. In order to do that, they have to use a `floating IP`.

Floating IPs are basically public IPv4 addresses that can be dynamically

attached and detached from VMs. The user creates a floating IP address from a

network that has set the `floating_ip_pool` attribute. The floating IP is

accounted to the user, who can then connect his VMs to public networks by