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81 lines
3.1 KiB
ReStructuredText
81 lines
3.1 KiB
ReStructuredText
.. _ceph-volume-simple-activate:
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``activate``
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============
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Once :ref:`ceph-volume-simple-scan` has been completed, and all the metadata
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captured for an OSD has been persisted to ``/etc/ceph/osd/{id}-{uuid}.json``
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the OSD is now ready to get "activated".
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This activation process **disables** all ``ceph-disk`` systemd units by masking
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them, to prevent the UDEV/ceph-disk interaction that will attempt to start them
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up at boot time.
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The disabling of ``ceph-disk`` units is done only when calling ``ceph-volume
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simple activate`` directly, but is avoided when being called by systemd when
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the system is booting up.
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The activation process requires using both the :term:`OSD id` and :term:`OSD uuid`
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To activate parsed OSDs::
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ceph-volume simple activate 0 6cc43680-4f6e-4feb-92ff-9c7ba204120e
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The above command will assume that a JSON configuration will be found in::
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/etc/ceph/osd/0-6cc43680-4f6e-4feb-92ff-9c7ba204120e.json
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Alternatively, using a path to a JSON file directly is also possible::
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ceph-volume simple activate --file /etc/ceph/osd/0-6cc43680-4f6e-4feb-92ff-9c7ba204120e.json
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requiring uuids
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^^^^^^^^^^^^^^^
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The :term:`OSD uuid` is being required as an extra step to ensure that the
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right OSD is being activated. It is entirely possible that a previous OSD with
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the same id exists and would end up activating the incorrect one.
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Discovery
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---------
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With OSDs previously scanned by ``ceph-volume``, a *discovery* process is
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performed using ``blkid`` and ``lvm``. There is currently support only for
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devices with GPT partitions and LVM logical volumes.
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The GPT partitions will have a ``PARTUUID`` that can be queried by calling out
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to ``blkid``, and the logical volumes will have a ``lv_uuid`` that can be
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queried against ``lvs`` (the LVM tool to list logical volumes).
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This discovery process ensures that devices can be correctly detected even if
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they are repurposed into another system or if their name changes (as in the
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case of non-persisting names like ``/dev/sda1``)
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The JSON configuration file used to map what devices go to what OSD will then
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coordinate the mounting and symlinking as part of activation.
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To ensure that the symlinks are always correct, if they exist in the OSD
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directory, the symlinks will be re-done.
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A systemd unit will capture the :term:`OSD id` and :term:`OSD uuid` and
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persist it. Internally, the activation will enable it like::
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systemctl enable ceph-volume@simple-$id-$uuid
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For example::
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systemctl enable ceph-volume@simple-0-8715BEB4-15C5-49DE-BA6F-401086EC7B41
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Would start the discovery process for the OSD with an id of ``0`` and a UUID of
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``8715BEB4-15C5-49DE-BA6F-401086EC7B41``.
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The systemd process will call out to activate passing the information needed to
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identify the OSD and its devices, and it will proceed to:
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# mount the device in the corresponding location (by convention this is
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``/var/lib/ceph/osd/<cluster name>-<osd id>/``)
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# ensure that all required devices are ready for that OSD and properly linked,
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regardless of objectstore used (filestore or bluestore). The symbolic link will
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**always** be re-done to ensure that the correct device is linked.
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# start the ``ceph-osd@0`` systemd unit
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