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<!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [ |
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<!-- Please adjust the date whenever revising the manpage. --> |
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<!ENTITY dhdate "<date>June 08, 2010</date>"> |
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<!-- SECTION should be 1-8, maybe w/ subsection other parameters are |
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allowed: see man(7), man(1). --> |
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<!ENTITY dhsection "<manvolnum>8</manvolnum>"> |
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<!ENTITY dhucpackage "<refentrytitle>ganeti-masterd</refentrytitle>"> |
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<!ENTITY dhpackage "ganeti-masterd"> |
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<!ENTITY debian "<productname>Debian</productname>"> |
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<!ENTITY gnu "<acronym>GNU</acronym>"> |
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<!ENTITY gpl "&gnu; <acronym>GPL</acronym>"> |
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<!ENTITY footer SYSTEM "footer.sgml"> |
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]> |
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|
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<refentry> |
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<refentryinfo> |
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<copyright> |
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<year>2008</year> |
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<year>2009</year> |
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<year>2010</year> |
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<holder>Google Inc.</holder> |
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</copyright> |
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&dhdate; |
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</refentryinfo> |
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<refmeta> |
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&dhucpackage; |
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|
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&dhsection; |
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<refmiscinfo>Ganeti 2.2</refmiscinfo> |
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</refmeta> |
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<refnamediv> |
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<refname>&dhpackage;</refname> |
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|
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<refpurpose>Ganeti master daemon</refpurpose> |
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</refnamediv> |
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<refsynopsisdiv> |
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<cmdsynopsis> |
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<command>&dhpackage; </command> |
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<arg>-f</arg> |
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<arg>-d</arg> |
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<arg>--no-voting</arg> |
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|
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</cmdsynopsis> |
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</refsynopsisdiv> |
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<refsect1> |
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<title>DESCRIPTION</title> |
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|
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<para> |
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The <command>&dhpackage;</command> is the daemon which is |
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responsible for the overall cluster coordination. Without it, no |
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change can be performed on the cluster. |
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</para> |
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|
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<para> |
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For testing purposes, you can give the <option>-f</option> |
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option and the program won't detach from the running terminal. |
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</para> |
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|
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<para> |
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Debug-level message can be activated by giving the |
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<option>-d</option> option. |
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</para> |
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<refsect2> |
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<title>ROLE</title> |
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<para> |
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The role of the master daemon is to coordinate all the actions |
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that change the state of the cluster. Things like accepting |
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new jobs, coordinating the changes on nodes (via RPC calls to |
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the respective node daemons), maintaining the configuration |
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and so on are done via this daemon. |
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</para> |
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|
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<para> |
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The only action that can be done without the master daemon is |
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the failover of the master role to another node in the |
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cluster, via the <command>gnt-cluster masterfailover</command> |
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command. |
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</para> |
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|
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<para> |
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If the master daemon is stopped, the instances are not |
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affected, but they won't be restarted automatically in case of |
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failure. |
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</para> |
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</refsect2> |
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|
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<refsect2> |
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<title>STARTUP</title> |
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<para> |
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At startup, the master daemon will confirm with the node |
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daemons that the node it is running is indeed the master node |
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of the cluster. It will abort if it doesn't get half plus one |
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positive answers (offline nodes are queried too, just in case |
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our configuration is stale). |
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</para> |
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|
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<para> |
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For small clusters with a number of nodes down, and especially |
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for two-node clusters where the other has gone done, this |
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creates a problem. In this case the |
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<option>--no-voting</option> option can be used to skip this |
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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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</para> |
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</refsect2> |
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|
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<refsect2> |
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<title>JOB QUEUE</title> |
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<para> |
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The master daemon maintains a job queue (located under |
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<filename |
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class="directory">@LOCALSTATEDIR@/lib/ganeti/queue</filename>) in |
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which all current jobs are stored, one job per file serialized |
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in JSON format; in this directory a subdirectory called |
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<filename class="directory">archive</filename> holds archived |
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job files. |
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</para> |
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|
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<para> |
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The moving of jobs from the current to the queue directory is |
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done via a request to the master; this can be accomplished |
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from the command line with the <command>gnt-job |
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archive</command> or <command>gnt-job autoarchive</command> |
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commands. In case of problems with the master, a job file can |
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simply be moved away or deleted (but this might leave the |
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cluster inconsistent). |
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</para> |
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|
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</refsect2> |
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|
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<refsect2> |
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<title>COMMUNICATION PROTOCOL</title> |
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<para> |
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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 |
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more details, see the design documentation supplied with |
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Ganeti. |
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</para> |
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</refsect2> |
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|
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</refsect1> |
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|
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&footer; |
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|
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</refentry> |
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