mount.ceph – mount a Ceph file system


mount.ceph [mon1_socket,mon2_socket,…]:/[subdir] dir [ -o options ]


mount.ceph is a helper for mounting the Ceph file system on a Linux host. It serves to resolve monitor hostname(s) into IP addresses and read authentication keys from disk; the Linux kernel client component does most of the real work. In fact, it is possible to mount a non-authenticated Ceph file system without mount.ceph by specifying monitor address(es) by IP:

mount -t ceph /mnt/mycephfs

The first argument is the device part of the mount command. It includes host’s socket and path within CephFS that will be mounted at the mount point. The socket, obviously, takes the form ip_address[:port]. If the port is not specified, the Ceph default of 6789 is assumed. Multiple monitor addresses can be passed by separating them by commas. Only one monitor is needed to mount successfully; the client will learn about all monitors from any responsive monitor. However, it is a good idea to specify more than one in case the one happens to be down at the time of mount.

If the host portion of the device is left blank, then mount.ceph will attempt to determine monitor addresses using local configuration files and/or DNS SRV records. In similar way, if authentication is enabled on Ceph cluster (which is done using CephX) and options secret and secretfile are not specified in the command, the mount helper will spawn a child process that will use the standard Ceph library routines to find a keyring and fetch the secret from it.

A sub-directory of the file system can be mounted by specifying the (absolute) path to the sub-directory right after “:” after the socket in the device part of the mount command.

Mount helper application conventions dictate that the first two options are device to be mounted and the mountpoint for that device. Options must be passed only after these fixed arguments.




Path to a ceph.conf file. This is used to initialize the Ceph context for autodiscovery of monitor addresses and auth secrets. The default is to use the standard search path for ceph.conf files.


fs=<fs-name> Specify the non-default file system to be mounted. Not passing this option mounts the default file system.


mds_namespace=<fs-name> A synonym of “fs=” and its use is deprecated.


int (seconds), Default: 60


Set the connection mode that the client uses for transport. The available modes are:

  • legacy: use messenger v1 protocol to talk to the cluster

  • crc: use messenger v2, without on-the-wire encryption

  • secure: use messenger v2, with on-the-wire encryption

  • prefer-crc: crc mode, if denied agree to secure mode

  • prefer-secure: secure mode, if denied agree to crc mode


RADOS user to authenticate as when using CephX. Default: guest


secret key for use with CephX. This option is insecure because it exposes the secret on the command line. To avoid this, use the secretfile option.


path to file containing the secret key to use with CephX


Set auto reconnect mode in the case where the client is blocklisted. The available modes are no and clean. The default is no.

  • no: never attempt to reconnect when client detects that it has been

    blocklisted. Blocklisted clients will not attempt to reconnect and their operations will fail too.

  • clean: client reconnects to the Ceph cluster automatically when it detects that it has been blocklisted. During reconnect, client drops dirty data/metadata, invalidates page caches and writable file handles. After reconnect, file locks become stale because the MDS loses track of them. If an inode contains any stale file locks, read/write on the inode is not allowed until applications release all stale file locks.


fs=<fs-name> Specify the non-default file system to be mounted, when using the old syntax.


mds_namespace=<fs-name> A synonym of “fs=” (Deprecated).



int, Default: calculated


int, cap release delay, Default: 60


int, cap release delay, Default: 5


funky cat dirname for stats, Default: off


no funky cat dirname for stats


my ip


no dcache readdir


no data crc on writes


create a new client instance, instead of sharing an existing instance of a client mounting the same cluster


int, Default: 5


int (seconds), Default: 60


int (bytes), max readahead. Default: 8388608 (8192*1024)


Report the recursive size of the directory contents for st_size on directories. Default: off


Do not report the recursive size of the directory contents for st_size on directories.


int, Default: 524288 (512*1024)


int, Default: 1024


int (bytes), max read size. Default: 16777216 (16*1024*1024)


string, set the name of the hidden snapdir. Default: .snap


int (kb), max writeback in flight. scale with available memory. Default: calculated from available memory


int (bytes), max write size. Default: 16777216 (16*1024*1024) (writeback uses smaller of wsize and stripe unit)


Execute all namespace operations synchronously. This ensures that the namespace operation will only complete after receiving a reply from the MDS. This is the default.


Allow the client to do namespace operations asynchronously. When this option is enabled, a namespace operation may complete before the MDS replies, if it has sufficient capabilities to do so.


Mount the full file system:

mount.ceph :/ /mnt/mycephfs

Assuming mount.ceph is installed properly, it should be automatically invoked by mount(8):

mount -t ceph :/ /mnt/mycephfs

Mount only part of the namespace/file system:

mount.ceph :/some/directory/in/cephfs /mnt/mycephfs
Mount non-default FS, in case cluster has multiple FSs::

mount -t ceph :/ /mnt/mycephfs2 -o fs=mycephfs2


mount -t ceph :/ /mnt/mycephfs2 -o mds_namespace=mycephfs2 # This option name is deprecated.

Pass the monitor host’s IP address, optionally:

mount.ceph /mnt/mycephfs

Pass the port along with IP address if it’s running on a non-standard port:

mount.ceph /mnt/mycephfs

If there are multiple monitors, passes addresses separated by a comma:

mount.ceph,, /mnt/mycephfs

If authentication is enabled on Ceph cluster:

mount.ceph :/ /mnt/mycephfs -o name=fs_username

Pass secret key for CephX user optionally:

mount.ceph :/ /mnt/mycephfs -o name=fs_username,secret=AQATSKdNGBnwLhAAnNDKnH65FmVKpXZJVasUeQ==

Pass file containing secret key to avoid leaving secret key in shell’s command history:

mount.ceph :/ /mnt/mycephfs -o name=fs_username,secretfile=/etc/ceph/fs_username.secret

To mount using the old syntax:

mount -t ceph /mnt/mycephfs


mount.ceph is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at for more information.

Feature Availability

The recover_session= option was added to mainline Linux kernels in v5.4. wsync and nowsync were added in v5.7.

See also

ceph-fuse(8), ceph(8)