Synnefo » snf-ganeti » ganeti-local

ganeti(7) Ganeti | Version @GANETI_VERSION@

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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.

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 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.