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387 lines
10 KiB
ReStructuredText
.. _cephfs-administration:
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CephFS Administrative commands
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==============================
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File Systems
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------------
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.. note:: The names of the file systems, metadata pools, and data pools can
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only have characters in the set [a-zA-Z0-9\_-.].
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These commands operate on the CephFS file systems in your Ceph cluster.
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Note that by default only one file system is permitted: to enable
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creation of multiple file systems use ``ceph fs flag set enable_multiple true``.
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::
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fs new <file system name> <metadata pool name> <data pool name>
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This command creates a new file system. The file system name and metadata pool
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name are self-explanatory. The specified data pool is the default data pool and
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cannot be changed once set. Each file system has its own set of MDS daemons
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assigned to ranks so ensure that you have sufficient standby daemons available
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to accommodate the new file system.
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::
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fs ls
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List all file systems by name.
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::
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fs dump [epoch]
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This dumps the FSMap at the given epoch (default: current) which includes all
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file system settings, MDS daemons and the ranks they hold, and the list of
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standby MDS daemons.
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::
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fs rm <file system name> [--yes-i-really-mean-it]
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Destroy a CephFS file system. This wipes information about the state of the
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file system from the FSMap. The metadata pool and data pools are untouched and
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must be destroyed separately.
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::
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fs get <file system name>
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Get information about the named file system, including settings and ranks. This
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is a subset of the same information from the ``fs dump`` command.
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::
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fs set <file system name> <var> <val>
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Change a setting on a file system. These settings are specific to the named
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file system and do not affect other file systems.
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::
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fs add_data_pool <file system name> <pool name/id>
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Add a data pool to the file system. This pool can be used for file layouts
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as an alternate location to store file data.
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::
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fs rm_data_pool <file system name> <pool name/id>
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This command removes the specified pool from the list of data pools for the
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file system. If any files have layouts for the removed data pool, the file
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data will become unavailable. The default data pool (when creating the file
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system) cannot be removed.
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Settings
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--------
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::
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fs set <fs name> max_file_size <size in bytes>
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CephFS has a configurable maximum file size, and it's 1TB by default.
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You may wish to set this limit higher if you expect to store large files
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in CephFS. It is a 64-bit field.
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Setting ``max_file_size`` to 0 does not disable the limit. It would
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simply limit clients to only creating empty files.
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Maximum file sizes and performance
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----------------------------------
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CephFS enforces the maximum file size limit at the point of appending to
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files or setting their size. It does not affect how anything is stored.
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When users create a file of an enormous size (without necessarily
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writing any data to it), some operations (such as deletes) cause the MDS
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to have to do a large number of operations to check if any of the RADOS
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objects within the range that could exist (according to the file size)
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really existed.
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The ``max_file_size`` setting prevents users from creating files that
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appear to be eg. exabytes in size, causing load on the MDS as it tries
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to enumerate the objects during operations like stats or deletes.
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Taking the cluster down
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-----------------------
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Taking a CephFS cluster down is done by setting the down flag:
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fs set <fs_name> down true
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To bring the cluster back online:
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::
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fs set <fs_name> down false
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This will also restore the previous value of max_mds. MDS daemons are brought
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down in a way such that journals are flushed to the metadata pool and all
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client I/O is stopped.
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Taking the cluster down rapidly for deletion or disaster recovery
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-----------------------------------------------------------------
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To allow rapidly deleting a file system (for testing) or to quickly bring the
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file system and MDS daemons down, use the ``fs fail`` command:
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::
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fs fail <fs_name>
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This command sets a file system flag to prevent standbys from
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activating on the file system (the ``joinable`` flag).
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This process can also be done manually by doing the following:
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::
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fs set <fs_name> joinable false
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Then the operator can fail all of the ranks which causes the MDS daemons to
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respawn as standbys. The file system will be left in a degraded state.
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::
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# For all ranks, 0-N:
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mds fail <fs_name>:<n>
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Once all ranks are inactive, the file system may also be deleted or left in
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this state for other purposes (perhaps disaster recovery).
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To bring the cluster back up, simply set the joinable flag:
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::
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fs set <fs_name> joinable true
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Daemons
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-------
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Most commands manipulating MDSs take a ``<role>`` argument which can take one
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of three forms:
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::
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<fs_name>:<rank>
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<fs_id>:<rank>
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<rank>
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Commands to manipulate MDS daemons:
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::
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mds fail <gid/name/role>
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Mark an MDS daemon as failed. This is equivalent to what the cluster
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would do if an MDS daemon had failed to send a message to the mon
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for ``mds_beacon_grace`` second. If the daemon was active and a suitable
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standby is available, using ``mds fail`` will force a failover to the standby.
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If the MDS daemon was in reality still running, then using ``mds fail``
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will cause the daemon to restart. If it was active and a standby was
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available, then the "failed" daemon will return as a standby.
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tell mds.<daemon name> command ...
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Send a command to the MDS daemon(s). Use ``mds.*`` to send a command to all
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daemons. Use ``ceph tell mds.* help`` to learn available commands.
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mds metadata <gid/name/role>
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Get metadata about the given MDS known to the Monitors.
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mds repaired <role>
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Mark the file system rank as repaired. Unlike the name suggests, this command
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does not change a MDS; it manipulates the file system rank which has been
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marked damaged.
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Minimum Client Version
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----------------------
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It is sometimes desirable to set the minimum version of Ceph that a client must be
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running to connect to a CephFS cluster. Older clients may sometimes still be
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running with bugs that can cause locking issues between clients (due to
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capability release). CephFS provides a mechanism to set the minimum
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client version:
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fs set <fs name> min_compat_client <release>
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For example, to only allow Nautilus clients, use:
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fs set cephfs min_compat_client nautilus
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Clients running an older version will be automatically evicted.
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Enforcing minimum version of CephFS client is achieved by setting required
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client features. Commands to manipulate required client features of a file
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system:
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::
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fs required_client_features <fs name> add reply_encoding
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fs required_client_features <fs name> rm reply_encoding
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To list all CephFS features
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fs feature ls
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CephFS features and first release they came out.
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+------------------+--------------+-----------------+
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| Feature | Ceph release | Upstream Kernel |
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+==================+==============+=================+
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| jewel | jewel | 4.5 |
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+------------------+--------------+-----------------+
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| kraken | kraken | 4.13 |
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+------------------+--------------+-----------------+
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| luminous | luminous | 4.13 |
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+------------------+--------------+-----------------+
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| mimic | mimic | 4.19 |
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+------------------+--------------+-----------------+
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| reply_encoding | nautilus | 5.1 |
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+------------------+--------------+-----------------+
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| reclaim_client | nautilus | N/A |
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+------------------+--------------+-----------------+
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| lazy_caps_wanted | nautilus | 5.1 |
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+------------------+--------------+-----------------+
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| multi_reconnect | nautilus | 5.1 |
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+------------------+--------------+-----------------+
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| deleg_ino | octopus | 5.6 |
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+------------------+--------------+-----------------+
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| metric_collect | pacific | N/A |
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+------------------+--------------+-----------------+
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CephFS Feature Descriptions
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reply_encoding
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MDS encodes request reply in extensible format if client supports this feature.
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reclaim_client
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MDS allows new client to reclaim another (dead) client's states. This feature
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is used by NFS-Ganesha.
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lazy_caps_wanted
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When a stale client resumes, if the client supports this feature, mds only needs
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to re-issue caps that are explicitly wanted.
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multi_reconnect
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When mds failover, client sends reconnect messages to mds, to reestablish cache
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states. If MDS supports this feature, client can split large reconnect message
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into multiple ones.
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deleg_ino
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MDS delegate inode numbers to client if client supports this feature. Having
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delegated inode numbers is a prerequisite for client to do async file creation.
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metric_collect
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Clients can send performance metric to MDS if MDS support this feature.
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Global settings
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---------------
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fs flag set <flag name> <flag val> [<confirmation string>]
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Sets a global CephFS flag (i.e. not specific to a particular file system).
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Currently, the only flag setting is 'enable_multiple' which allows having
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multiple CephFS file systems.
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Some flags require you to confirm your intentions with "--yes-i-really-mean-it"
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or a similar string they will prompt you with. Consider these actions carefully
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before proceeding; they are placed on especially dangerous activities.
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Advanced
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--------
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These commands are not required in normal operation, and exist
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for use in exceptional circumstances. Incorrect use of these
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commands may cause serious problems, such as an inaccessible
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file system.
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mds compat rm_compat
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Removes an compatibility feature flag.
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mds compat rm_incompat
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Removes an incompatibility feature flag.
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mds compat show
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Show MDS compatibility flags.
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mds rmfailed
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This removes a rank from the failed set.
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fs reset <file system name>
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This command resets the file system state to defaults, except for the name and
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pools. Non-zero ranks are saved in the stopped set.
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