mirror of
https://github.com/ceph/ceph
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7367382ef2
"fs" is one alias for "mds_namespace=" and it will be cleaner and be more user-friendly to use. The "fs" will be translated to "mds_namespace" before sending it to kernel space. And the "mds_namespace" will be deprecated to use any more. Update the documents at the same time. Fixes: https://tracker.ceph.com/issues/44214 Signed-off-by: Xiubo Li <xiubli@redhat.com>
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132 lines
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=================================
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Mount CephFS using Kernel Driver
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=================================
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The CephFS kernel driver is part of the Linux kernel. It allows mounting
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CephFS as a regular file system with native kernel performance. It is the
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client of choice for most use-cases.
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Prerequisites
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=============
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Complete General Prerequisites
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------------------------------
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Go through the prerequisites required by both, kernel as well as FUSE mounts,
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in `Mount CephFS: Prerequisites`_ page.
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Is mount helper is present?
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---------------------------
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``mount.ceph`` helper is installed by Ceph packages. The helper passes the
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monitor address(es) and CephX user keyrings automatically saving the Ceph
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admin the effort to pass these details explicitly while mountng CephFS. In
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case the helper is not present on the client machine, CephFS can still be
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mounted using kernel but by passing these details explicitly to the ``mount``
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command. To check whether it is present on your system, do::
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stat /sbin/mount.ceph
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Which Kernel Version?
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---------------------
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Because the kernel client is distributed as part of the linux kernel (not
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as part of packaged ceph releases), you will need to consider which kernel
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version to use on your client nodes. Older kernels are known to include buggy
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ceph clients, and may not support features that more recent Ceph clusters
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support.
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Remember that the "latest" kernel in a stable linux distribution is likely
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to be years behind the latest upstream linux kernel where Ceph development
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takes place (including bug fixes).
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As a rough guide, as of Ceph 10.x (Jewel), you should be using a least a 4.x
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kernel. If you absolutely have to use an older kernel, you should use the
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fuse client instead of the kernel client.
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This advice does not apply if you are using a linux distribution that
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includes CephFS support, as in this case the distributor will be responsible
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for backporting fixes to their stable kernel: check with your vendor.
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Synopsis
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========
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In general, the command to mount CephFS via kernel driver looks like this::
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mount -t ceph {device-string}:{path-to-mounted} {mount-point} -o {key-value-args} {other-args}
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Mounting CephFS
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===============
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On Ceph clusters, CephX is enabled by default. Use ``mount`` command to
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mount CephFS with the kernel driver::
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mkdir /mnt/mycephfs
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mount -t ceph :/ /mnt/mycephfs -o name=foo
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The key-value argument right after option ``-o`` is CephX credential;
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``name`` is the username of the CephX user we are using to mount CephFS. The
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default value for ``name`` is ``guest``.
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The kernel driver also requires MON's socket and the secret key for the CephX
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user. In case of the above command, ``mount.ceph`` helper figures out these
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details automatically by finding and reading Ceph conf file and keyring. In
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case you don't have these files on the host where you're running mount
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command, you can pass these details yourself too::
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mount -t ceph 192.168.0.1:6789,192.168.0.2:6789:/ /mnt/mycephfs -o name=foo,secret=AQATSKdNGBnwLhAAnNDKnH65FmVKpXZJVasUeQ==
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Passing a single MON socket in above command works too. A potential problem
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with the command above is that the secret key is left in your shell's command
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history. To prevent that you can copy the secret key inside a file and pass
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the file by using the option ``secretfile`` instead of ``secret``::
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mount -t ceph :/ /mnt/mycephfs -o name=foo,secretfile=/etc/ceph/foo.secret
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Ensure the permissions on the secret key file are appropriate (preferably,
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``600``).
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In case CephX is disabled, you can omit ``-o`` and the list of key-value
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arguments that follow it::
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mount -t ceph :/ /mnt/mycephfs
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To mount a subtree of the CephFS root, append the path to the device string::
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mount -t ceph :/subvolume/dir1/dir2 /mnt/mycephfs -o name=fs
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If you have more than one file system on your Ceph cluster, you can mount the
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non-default FS as follows::
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mount -t ceph :/ /mnt/mycephfs2 -o name=fs,fs=mycephfs2
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Unmounting CephFS
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=================
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To unmount the Ceph file system, use the ``umount`` command as usual::
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umount /mnt/mycephfs
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.. tip:: Ensure that you are not within the file system directories before
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executing this command.
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Persistent Mounts
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==================
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To mount CephFS in your file systems table as a kernel driver, add the
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following to ``/etc/fstab``::
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[{ipaddress}:{port}]:/ {mount}/{mountpoint} ceph [name=username,secret=secretkey|secretfile=/path/to/secretfile],[{mount.options}]
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For example::
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:/ /mnt/ceph ceph name=admin,noatime,_netdev 0 2
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The default for the ``name=`` parameter is ``guest``. If the ``secret`` or
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``secretfile`` options are not specified then the mount helper will attempt to
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find a secret for the given ``name`` in one of the configured keyrings.
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See `User Management`_ for details on CephX user management and mount.ceph_
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manual for more options it can take. For troubleshooting, see
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:ref:`kernel_mount_debugging`.
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.. _fstab: ../fstab/#kernel-driver
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.. _Mount CephFS\: Prerequisites: ../mount-prerequisites
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.. _mount.ceph: ../../man/8/mount.ceph/
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.. _User Management: ../../rados/operations/user-management/
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