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https://github.com/ceph/ceph
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87 lines
3.0 KiB
ReStructuredText
87 lines
3.0 KiB
ReStructuredText
==============================
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Resizing the monitor cluster
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==============================
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Adding a monitor
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----------------
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#. Initialize the new monitor's data directory with the ``ceph-mon
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--mkfs`` command. You need to provide the new monitor with three
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pieces of information:
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- the cluster fsid. This can come from a monmap (``--monmap
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</path/to/monmap>``) for explicitly via ``--fsid <fsid>``.
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- one or more existing monitors to join. This can come via ``-m
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<host1,host2,...>``, a monmap (``--monmap </some/path>``), or
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``[mon.foo]`` sections with ``mon addr`` fields in *ceph.conf*.
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- the monitor authentication key ``mon.``. This should be passed
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in explicitly via a keyring (``--keyring </some/path>``).
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Any combination of the above arguments that provide the four needed
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pieces of information will work. The simplest way to do this is
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usually::
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$ ceph mon getmap -o /tmp/monmap # provides fsid and existing monitor addrs
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$ ceph auth export mon. -o /tmp/monkey # mon. auth key
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$ ceph-mon -i newname --mkfs --monmap /tmp/monmap --keyring /tmp/monkey
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#. Start the new monitor and it will automatically join the cluster.
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The daemon needs to know which address to bind to, either via
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``--public-addr <ip:port>`` or by setting ``mon addr`` in the
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appropriate section of *ceph.conf*. For example::
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$ ceph-mon -i newname --public-addr <ip:port>
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#. If you would like other nodes to be able to use this monitor during
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their initial startup, you'll need to adjust *ceph.conf* to add a
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section and ``mon addr`` for the new monitor, or add it to the
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existing ``mon host`` list.
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Removing a monitor from a healthy cluster
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-----------------------------------------
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If the cluster is healthy, you can do::
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$ ceph mon remove $id
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For example, if your cluster includes ``mon.a``, ``mon.b``, and ``mon.c``, then you can remove ``mon.c`` with::
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$ ceph mon remove c
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Removing a monitor from an unhealthy or down cluster
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----------------------------------------------------
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The mon cluster may not be up because you have lost too many nodes to
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form a quorum.
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#) On a surviving monitor node, find the most recent monmap::
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$ ls $mon_data/monmap
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1 2 accepted_pn last_committed latest
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in this case it is 2.
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#) Copy to a temporary location and modify the monmap to remove the
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node(s) you don't want. Let's say the map has ``mon.a``, ``mon.b``,
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and ``mon.c``, but only ``mon.a`` is surviving::
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$ cp $mon_data/monmap/2 /tmp/foo
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$ monmaptool /tmp/foo --rm b
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$ monmaptool /tmp/foo --rm c
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3) Make sure ceph-mon isn't running::
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$ service ceph stop mon
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4) Inject the modified map on any surviving nodes. For example, for
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``mon.a``::
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$ ceph-mon -i a --inject-monmap /tmp/foo # for each surviving monitor
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5) Start the surviving monitor(s)::
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$ service ceph start mon # on each node with a surviving monitor
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6) Remove the old monitors from *ceph.conf* so that nobody tries to
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connect to the old instances.
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