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ganeti-masterd(8) Ganeti | Version @GANETI_VERSION@
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===================================================
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Name
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----
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ganeti-masterd - Ganeti master daemon
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Synopsis
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--------
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**ganeti-masterd** [-f] [-d] [--no-voting]
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DESCRIPTION
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-----------
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The **ganeti-masterd** is the daemon which is responsible for the
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overall cluster coordination. Without it, no change can be
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performed on the cluster.
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For testing purposes, you can give the ``-f`` option and the
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program won't detach from the running terminal.
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Debug-level message can be activated by giving the ``-d`` option.
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ROLE
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~~~~
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The role of the master daemon is to coordinate all the actions that
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change the state of the cluster. Things like accepting new jobs,
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coordinating the changes on nodes (via RPC calls to the respective
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node daemons), maintaining the configuration and so on are done via
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this daemon.
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The only action that can be done without the master daemon is the
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failover of the master role to another node in the cluster, via the
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**gnt-cluster master-failover** command.
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If the master daemon is stopped, the instances are not affected,
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but they won't be restarted automatically in case of failure.
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STARTUP
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~~~~~~~
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At startup, the master daemon will confirm with the node daemons
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that the node it is running is indeed the master node of the
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cluster. It will abort if it doesn't get half plus one positive
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answers (offline nodes are queried too, just in case our
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configuration is stale).
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For small clusters with a number of nodes down, and especially for
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two-node clusters where the other has gone done, this creates a
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problem. In this case the ``--no-voting`` option can be used to
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skip this process. The option requires interactive confirmation, as
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having two masters on the same cluster is a very dangerous
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situation and will most likely lead to data loss.
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JOB QUEUE
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~~~~~~~~~
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The master daemon maintains a job queue (located under the directory
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``@LOCALSTATEDIR@/lib/ganeti/queue``) in which all current jobs are
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stored, one job per file serialized in JSON format; in this directory
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a subdirectory called ``archive`` holds archived job files.
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The moving of jobs from the current to the queue directory is done
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via a request to the master; this can be accomplished from the
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command line with the **gnt-job archive** or
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**gnt-job autoarchive** commands. In case of problems with the
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master, a job file can simply be moved away or deleted (but this
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might leave the cluster inconsistent).
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COMMUNICATION PROTOCOL
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~~~~~~~~~~~~~~~~~~~~~~
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The master accepts commands over a Unix socket, using JSON
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serialized messages separated by a specific byte sequence. For more
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details, see the design documentation supplied with Ganeti.
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