Synnefo » snf-ganeti

ganeti(7) Ganeti | Version @GANETI_VERSION@

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

Name

----

ganeti - cluster-based virtualization management

Synopsis

--------

::

    # gnt-cluster init cluster1.example.com

    # gnt-node add node2.example.com

    # gnt-instance add -n node2.example.com \

    > -o debootstrap --disk 0:size=30g \

    > -t plain instance1.example.com

DESCRIPTION

-----------

The Ganeti software manages physical nodes and virtual instances of a

cluster based on a virtualization software. The current version (2.3)

supports Xen 3.x and KVM (72 or above) as hypervisors, and LXC as an

experimental hypervisor.

Quick start

-----------

First you must install the software on all the cluster nodes, either

from sources or (if available) from a package. The next step is to

create the initial cluster configuration, using **gnt-cluster init**.

Then you can add other nodes, or start creating instances.

Cluster architecture

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

In Ganeti 2.0, the architecture of the cluster is a little more

complicated than in 1.2. The cluster is coordinated by a master daemon

(**ganeti-masterd**(8)), running on the master node. Each node runs

(as before) a node daemon, and the master has the RAPI daemon running

too.

Node roles

~~~~~~~~~~

Each node can be in one of the following states:

master

    Only one node per cluster can be in this role, and this node is the

    one holding the authoritative copy of the cluster configuration and

    the one that can actually execute commands on the cluster and

    modify the cluster state. See more details under

    *Cluster configuration*.

master_candidate

    The node receives the full cluster configuration (configuration

    file and jobs) and can become a master via the

    **gnt-cluster master-failover** command. Nodes that are not in this

    state cannot transition into the master role due to missing state.

regular

    This the normal state of a node.

drained

    Nodes in this state are functioning normally but cannot receive

    new instances, because the intention is to set them to *offline*

    or remove them from the cluster.

offline

    These nodes are still recorded in the Ganeti configuration, but

    except for the master daemon startup voting procedure, they are not

    actually contacted by the master. This state was added in order to

    allow broken machines (that are being repaired) to remain in the

    cluster but without creating problems.

Node flags

~~~~~~~~~~

Nodes have two flags which govern which roles they can take:

master_capable

    The node can become a master candidate, and furthermore the master

    node. When this flag is disabled, the node cannot become a

    candidate; this can be useful for special networking cases, or less

    reliable hardware.

vm_capable

    The node can host instances. When enabled (the default state), the

    node will participate in instance allocation, capacity calculation,

    etc. When disabled, the node will be skipped in many cluster checks

    and operations.

Node Parameters

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

These parameters are node specific and can be preseeded on node-group

and cluster level.

Currently we support the following node parameters:

oob_program

    Path to an executable used as the out-of-band helper as described in

    the `Ganeti Node OOB Management Framework <design-oob.rst>`_ design

    document.

Hypervisor State Parameters

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

Using ``--hypervisor-state`` you can set hypervisor specific states as

pointed out in ``Ganeti Resource Model <design-resource-model.rst>``.

The format is: ``hypervisor:option=value``.

Currently we support the following hypervisor state values:

mem_total

  Total node memory, as discovered by this hypervisor

mem_node

  Memory used by, or reserved for, the node itself; note that some

  hypervisors can report this in an authoritative way, other not

mem_hv

  Memory used either by the hypervisor itself or lost due to instance

  allocation rounding; usually this cannot be precisely computed, but

  only roughly estimated

cpu_total

  Total node cpu (core) count; usually this can be discovered

  automatically

cpu_node

  Number of cores reserved for the node itself; this can either be

  discovered or set manually. Only used for estimating how many VCPUs

  are left for instances

Disk State Parameters

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

Using ``--disk-state`` you can set disk specific states as pointed out

in ``Ganeti Resource Model <design-resource-model.rst>``.

The format is: ``storage_type/identifier:option=value``. Where we

currently just support ``lvm`` as storage type. The identifier in this

case is the LVM volume group. By default this is ``xenvg``.

Currently we support the following hypervisor state values:

disk_total

  Total disk size (usually discovered automatically)

disk_reserved

  Reserved disk size; this is a lower limit on the free space, if such a

  limit is desired

disk_overhead

  Disk that is expected to be used by other volumes (set via

  ``reserved_lvs``); usually should be zero

Cluster configuration

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

The master node keeps and is responsible for the cluster

configuration. On the filesystem, this is stored under the

``@LOCALSTATEDIR@/ganeti/lib`` directory, and if the master daemon is

stopped it can be backed up normally.

The master daemon will replicate the configuration database called

``config.data`` and the job files to all the nodes in the master

candidate role. It will also distribute a copy of some configuration

values via the *ssconf* files, which are stored in the same directory

and start with a ``ssconf_`` prefix, to all nodes.

Jobs

~~~~

All cluster modification are done via jobs. A job consists of one

or more opcodes, and the list of opcodes is processed serially. If

an opcode fails, the entire job is failed and later opcodes are no

longer processed. A job can be in one of the following states:

queued

    The job has been submitted but not yet processed by the master

    daemon.

waiting

    The job is waiting for for locks before the first of its opcodes.

canceling

    The job is waiting for locks, but is has been marked for

    cancellation. It will not transition to *running*, but to

    *canceled*.

running

    The job is currently being executed.

canceled

    The job has been canceled before starting execution.

success

    The job has finished successfully.

error

    The job has failed during runtime, or the master daemon has been

    stopped during the job execution.

Common command line features

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

Options

~~~~~~~

Many Ganeti commands provide the following options. The

availability for a certain command can be checked by calling the

command using the ``--help`` option.

**gnt-...** *command* [--dry-run] [--priority {low | normal | high}]

The ``--dry-run`` option can be used to check whether an operation

would succeed.

The option ``--priority`` sets the priority for opcodes submitted

by the command.

Defaults

~~~~~~~~

For certain commands you can use environment variables to provide

default command line arguments. Just assign the arguments as a string to

the corresponding environment variable. The format of that variable

name is **binary**_*command*. **binary** is the name of the ``gnt-*``

script all upper case and dashes replaced by underscores, and *command*

is the command invoked on that script.

Currently supported commands are ``gnt-node list``, ``gnt-group list``

and ``gnt-instance list``. So you can configure default command line

flags by setting ``GNT_NODE_LIST``, ``GNT_GROUP_LIST`` and

``GNT_INSTANCE_LIST``.

Field formatting

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

Multiple ganeti commands use the same framework for tabular listing of

resources (e.g. **gnt-instance list**, **gnt-node list**, **gnt-group

list**, **gnt-debug locks**, etc.). For these commands, special states

are denoted via a special symbol (in terse mode) or a string (in

verbose mode):

\*, (offline)

    The node in question is marked offline, and thus it cannot be

    queried for data. This result is persistent until the node is

    de-offlined.

?, (nodata)

    Ganeti expected to receive an answer from this entity, but the

    cluster RPC call failed and/or we didn't receive a valid answer;

    usually more information is available in the node daemon log (if

    the node is alive) or the master daemon log. This result is

    transient, and re-running command might return a different result.

-, (unavail)

    The respective field doesn't make sense for this entity;

    e.g. querying a down instance for its current memory 'live' usage,

    or querying a non-vm_capable node for disk/memory data. This

    result is persistent, and until the entity state is changed via

    ganeti commands, the result won't change.

??, (unknown)

    This field is not known (note that this is different from entity

    being unknown). Either you have mis-typed the field name, or you

    are using a field that the running Ganeti master daemon doesn't

    know. This result is persistent, re-running the command won't

    change it.

Key-value parameters

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

Multiple options take parameters that are of the form

``key=value,key=value,...`` or ``category:key=value,...``. Examples

are the hypervisor parameters, backend parameters, etc. For these,

it's possible to use values that contain commas by escaping with via a

backslash (which needs two if not single-quoted, due to shell

behaviour)::

  # gnt-instance modify -H kernel_path=an\\,example instance1

  # gnt-instance modify -H kernel_path='an\,example' instance1

Query filters

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

Most commands listing resources (e.g. instances or nodes) support filtering.

The filter language is similar to Python expressions with some elements from

Perl. The language is not generic. Each condition must consist of a field name

and a value (except for boolean checks), a field can not be compared to another

field. Keywords are case-sensitive.

Syntax in pseudo-BNF::

  <quoted-string> ::= /* String quoted with single or double quotes,

                         backslash for escaping */

  <integer> ::= /* Number in base-10 positional notation */

  <re> ::= /* Regular expression */

  /*

    Modifier "i": Case-insensitive matching, see

    http://docs.python.org/library/re#re.IGNORECASE

    Modifier "s": Make the "." special character match any character,

    including newline, see http://docs.python.org/library/re#re.DOTALL

  */

  <re-modifiers> ::= /* empty */ | i | s

  <value> ::= <quoted-string> | <integer>

  <condition> ::=

    { /* Value comparison */

      <field> { == | != } <value>

      /* Collection membership */

      | <value> [ not ] in <field>

      /* Regular expressions (recognized delimiters

         are "/", "#", "^", and "|"; backslash for escaping)

      */

      | <field> { =~ | !~ } m/<re>/<re-modifiers>

      /* Globbing */

      | <field> { =* | !* } <quoted-string>

      /* Boolean */

      | <field>

    }

  <filter> ::=

    { [ not ] <condition> | ( <filter> ) }

    [ { and | or } <filter> ]

Operators:

*==*

  Equality

*!=*

  Inequality

*=~*

  Pattern match using regular expression

*!~*

  Logically negated from *=~*

*=\**

  Globbing, see **glob**(7), though only * and ? are supported

*!\**

  Logically negated from *=\**

*in*, *not in*

  Collection membership and negation

As a shortcut globbing patterns can be specified as names, e.g.

``gnt-instance list '*.site1' '*.site2'``.

Common daemon functionality

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

All Ganeti daemons re-open the log file(s) when sent a SIGHUP signal.

**logrotate**(8) can be used to rotate Ganeti's log files.

.. vim: set textwidth=72 :

.. Local Variables:

.. mode: rst

.. fill-column: 72

.. End: