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Merge pull request #52423 from zdover23/wip-doc-2023-07-13-rados-configuration-ceph-conf-1-of-x
doc/rados: edit ceph-conf.rst Reviewed-by: Anthony D'Atri <anthony.datri@gmail.com>
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Configuring Ceph
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==================
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When Ceph services start, the initialization process activates a series
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of daemons that run in the background. A :term:`Ceph Storage Cluster` runs
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at a minimum three types of daemons:
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When Ceph services start, the initialization process activates a series of
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daemons that run in the background. A :term:`Ceph Storage Cluster` runs at
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least three types of daemons:
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- :term:`Ceph Monitor` (``ceph-mon``)
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- :term:`Ceph Manager` (``ceph-mgr``)
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- :term:`Ceph OSD Daemon` (``ceph-osd``)
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Ceph Storage Clusters that support the :term:`Ceph File System` also run at
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least one :term:`Ceph Metadata Server` (``ceph-mds``). Clusters that
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support :term:`Ceph Object Storage` run Ceph RADOS Gateway daemons
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(``radosgw``) as well.
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least one :term:`Ceph Metadata Server` (``ceph-mds``). Clusters that support
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:term:`Ceph Object Storage` run Ceph RADOS Gateway daemons (``radosgw``).
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Each daemon has a number of configuration options, each of which has a
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default value. You may adjust the behavior of the system by changing these
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configuration options. Be careful to understand the consequences before
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Each daemon has a number of configuration options, each of which has a default
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value. You may adjust the behavior of the system by changing these
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configuration options. Be careful to understand the consequences before
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overriding default values, as it is possible to significantly degrade the
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performance and stability of your cluster. Also note that default values
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sometimes change between releases, so it is best to review the version of
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this documentation that aligns with your Ceph release.
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performance and stability of your cluster. Note too that default values
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sometimes change between releases. For this reason, it is best to review the
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version of this documentation that applies to your Ceph release.
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Option names
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============
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All Ceph configuration options have a unique name consisting of words
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formed with lower-case characters and connected with underscore
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(``_``) characters.
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Each of the Ceph configuration options has a unique name that consists of words
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formed with lowercase characters and connected with underscore characters
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(``_``).
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When option names are specified on the command line, either underscore
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(``_``) or dash (``-``) characters can be used interchangeable (e.g.,
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When option names are specified on the command line, underscore (``_``) and
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dash (``-``) characters can be used interchangeably (for example,
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``--mon-host`` is equivalent to ``--mon_host``).
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When option names appear in configuration files, spaces can also be
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used in place of underscore or dash. We suggest, though, that for
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clarity and convenience you consistently use underscores, as we do
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When option names appear in configuration files, spaces can also be used in
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place of underscores or dashes. However, for the sake of clarity and
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convenience, we suggest that you consistently use underscores, as we do
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throughout this documentation.
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Config sources
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==============
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Each Ceph daemon, process, and library will pull its configuration
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from several sources, listed below. Sources later in the list will
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override those earlier in the list when both are present.
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Each Ceph daemon, process, and library pulls its configuration from one or more
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of the several sources listed below. Sources that occur later in the list
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override those that occur earlier in the list (when both are present).
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- the compiled-in default value
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- the monitor cluster's centralized configuration database
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- a configuration file stored on the local host
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- environment variables
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- command line arguments
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- runtime overrides set by an administrator
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- command-line arguments
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- runtime overrides that are set by an administrator
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One of the first things a Ceph process does on startup is parse the
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configuration options provided via the command line, environment, and
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local configuration file. The process will then contact the monitor
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cluster to retrieve configuration stored centrally for the entire
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cluster. Once a complete view of the configuration is available, the
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daemon or process startup will proceed.
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configuration options provided via the command line, via the environment, and
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via the local configuration file. Next, the process contacts the monitor
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cluster to retrieve centrally-stored configuration for the entire cluster.
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After a complete view of the configuration is available, the startup of the
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daemon or process will commence.
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.. _bootstrap-options:
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Bootstrap options
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-----------------
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Some configuration options affect the process's ability to contact the
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monitors, to authenticate, and to retrieve the cluster-stored configuration.
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For this reason, these options might need to be stored locally on the node, and
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set by means of a local configuration file. These options include the
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following:
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Bootstrap options are configuration options that affect the process's ability
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to contact the monitors, to authenticate, and to retrieve the cluster-stored
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configuration. For this reason, these options might need to be stored locally
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on the node, and set by means of a local configuration file. These options
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include the following:
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.. confval:: mon_host
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.. confval:: mon_host_override
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- :confval:`mon_dns_srv_name`
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- :confval:`mon_data`, :confval:`osd_data`, :confval:`mds_data`, :confval:`mgr_data`, and
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similar options that define which local directory the daemon
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stores its data in.
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- :confval:`keyring`, :confval:`keyfile`, and/or :confval:`key`, which can be used to
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specify the authentication credential to use to authenticate with
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the monitor. Note that in most cases the default keyring location
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is in the data directory specified above.
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- :confval:`mon_data`, :confval:`osd_data`, :confval:`mds_data`,
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:confval:`mgr_data`, and similar options that define which local directory
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the daemon stores its data in.
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- :confval:`keyring`, :confval:`keyfile`, and/or :confval:`key`, which can be
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used to specify the authentication credential to use to authenticate with the
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monitor. Note that in most cases the default keyring location is in the data
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directory specified above.
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In most cases, there is no reason to modify the default values of these
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options. However, there is one exception to this: the :confval:`mon_host`
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option that identifies the addresses of the cluster's monitors. But when DNS is
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used to identify monitors, a local Ceph configuration file can be avoided
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entirely.
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In most cases, the default values of these options are suitable. There is one
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exception to this: the :confval:`mon_host` option that identifies the addresses
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of the cluster's monitors. When DNS is used to identify monitors, a local Ceph
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configuration file can be avoided entirely.
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Skipping monitor config
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-----------------------
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