Mount CephFS using FUSE

ceph-fuse is an alternate way of mounting CephFS, although it mounts it in userspace. Therefore, performance of FUSE can be relatively lower but FUSE clients can be more manageable, especially while upgrading CephFS.


Go through the prerequisites required by both, kernel as well as FUSE mounts, in Mount CephFS: Prerequisites page.


Mounting CephFS using FUSE requires superuser privileges to trim dentries by issuing a remount of itself.


In general, the command to mount CephFS via FUSE looks like this:

ceph-fuse {mountpoint} {options}

Mounting CephFS

To FUSE-mount the Ceph file system, use the ceph-fuse command:

mkdir /mnt/mycephfs
ceph-fuse --id foo /mnt/mycephfs

Option -id passes the name of the CephX user whose keyring we intend to use for mounting CephFS. In the above command, it’s foo. You can also use -n instead, although --id is evidently easier:

ceph-fuse -n /mnt/mycephfs

In case the keyring is not present in standard locations, you may pass it too:

ceph-fuse --id foo -k /path/to/keyring /mnt/mycephfs

You may pass the MON’s socket too, although this is not mandatory:

ceph-fuse --id foo -m /mnt/mycephfs

You can also mount a specific directory within CephFS instead of mounting root of CephFS on your local FS:

ceph-fuse --id foo -r /path/to/dir /mnt/mycephfs

If you have more than one FS on your Ceph cluster, use the option --client_fs to mount the non-default FS:

ceph-fuse --id foo --client_fs mycephfs2 /mnt/mycephfs2

You may also add a client_fs setting to your ceph.conf. Alternatively, the option --client_mds_namespace is supported for backward compatibility.

Unmounting CephFS

Use umount to unmount CephFS like any other FS:

umount /mnt/mycephfs


Ensure that you are not within the file system directories before executing this command.

Persistent Mounts

To mount CephFS as a file system in user space, add the following to /etc/fstab:

none    /mnt/mycephfs  fuse.ceph{user-ID}[,ceph.conf={path/to/conf.conf}],_netdev,defaults  0 0

For example:

none    /mnt/mycephfs  fuse.ceph,_netdev,defaults  0 0
none    /mnt/mycephfs  fuse.ceph,ceph.conf=/etc/ceph/foo.conf,_netdev,defaults  0 0

Ensure you use the ID (e.g., myuser, not client.myuser). You can pass any valid ceph-fuse option to the command line this way.

To mount a subdirectory of the CephFS, add the following to /etc/fstab:

none    /mnt/mycephfs  fuse.ceph,ceph.client_mountpoint=/path/to/dir,_netdev,defaults  0 0

ceph-fuse@.service and systemd units are available. As usual, these unit files declare the default dependencies and recommended execution context for ceph-fuse. After making the fstab entry shown above, run following commands:

systemctl start ceph-fuse@/mnt/mycephfs.service
systemctl enable
systemctl enable ceph-fuse@-mnt-mycephfs.service

See User Management for details on CephX user management and ceph-fuse manual for more options it can take. For troubleshooting, see ceph-fuse debugging.