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233 lines
5.1 KiB
ReStructuredText
233 lines
5.1 KiB
ReStructuredText
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CephFS Administrative commands
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==============================
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Filesystems
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-----------
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These commands operate on the CephFS filesystems in your Ceph cluster.
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Note that by default only one filesystem is permitted: to enable
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creation of multiple filesystems use ``ceph fs flag set enable_multiple true``.
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::
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fs new <filesystem name> <metadata pool name> <data pool name>
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::
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fs ls
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::
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fs rm <filesystem name> [--yes-i-really-mean-it]
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::
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fs reset <filesystem name>
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::
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fs get <filesystem name>
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::
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fs set <filesystem name> <var> <val>
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::
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fs add_data_pool <filesystem name> <pool name/id>
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::
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fs rm_data_pool <filesystem name> <pool name/id>
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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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::
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mds set <fs_name> down true
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To bring the cluster back online:
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::
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mds 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 MDS
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daemons down, the operator may also set a flag to prevent standbys from
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activating on the file system. This is done using the ``joinable`` flag:
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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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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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Comamnds 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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::
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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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::
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mds metadata <gid/name/role>
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::
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mds repaired <role>
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::
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mds stat
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Global settings
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---------------
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::
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fs dump
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::
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fs flag set <flag name> <flag val> [<confirmation string>]
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"flag name" must be one of ['enable_multiple']
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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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filesystem.
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::
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mds compat rm_compat
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::
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mds compat rm_incompat
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::
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mds compat show
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::
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mds set_state
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::
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mds rmfailed
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Legacy
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------
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These legacy commands are obsolete and no longer usable post-Luminous.
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::
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mds add_data_pool # replaced by "fs add_data_pool"
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mds cluster_down # replaced by "fs set cluster_down"
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mds cluster_up # replaced by "fs set cluster_up"
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mds dump # replaced by "fs get"
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mds getmap # replaced by "fs dump"
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mds newfs # replaced by "fs new"
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mds remove_data_pool # replaced by "fs rm_data_pool"
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mds set # replaced by "fs set"
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mds set_max_mds # replaced by "fs set max_mds"
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mds stop # obsolete
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