Mount CephFS using FUSE

Prerequisite

Before mounting CephFS, ensure that the client host (where CephFS has to be mounted and used) has a copy of the Ceph configuration file (i.e. ceph.conf) and a keyring of the CephX user that has CAPS for the Ceph MDS. Both of these files must be present on the host where the Ceph MON resides.

  1. Generate a minimal conf for the client host. The conf file should be placed at /etc/ceph:

    # on client host
    mkdir /etc/ceph
    ssh {user}@{mon-host} "sudo ceph config generate-minimal-conf" | sudo tee /etc/ceph/ceph.conf
    

    Alternatively, you may copy the conf file. But the method which generates the minimal config is usually sufficient. For more information, see Bootstrap options.

  2. Ensure that the conf has appropriate permissions:

    chmod 644 /etc/ceph/ceph.conf
    
  3. Create the CephX user and get its secret key:

    ssh {user}@{mon-host} "sudo ceph fs authorize cephfs client.foo / rw" | sudo tee /etc/ceph/ceph.client.foo.keyring
    

    In above command, replace cephfs with the name of your CephFS, foo by the name you want for your CephX user and / by the path within your CephFS for which you want to allow access to the client host and rw stands for both read and write permissions. Alternatively, you may copy the Ceph keyring from the MON host to client host at /etc/ceph but creating a keyring specific to the client host is better. While creating a CephX keyring/client, using same client name across multiple machines is perfectly fine.

Note

If you get 2 prompts for password while running above any of 2 above command, run sudo ls (or any other trivial command with sudo) immediately before these commands.

  1. Ensure that the keyring has appropriate permissions:

    chmod 600 /etc/ceph/ceph.client.foo.keyring
    

Synopsis

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 client.foo /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 192.168.0.1:6789 /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_mds_namespace to mount the non-default FS:

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

You may also add a client_mds_namespace setting to your ceph.conf

Unmounting CephFS

Use umount to unmount CephFS like any other FS:

umount /mnt/mycephfs

Tip

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:

#DEVICE PATH       TYPE      OPTIONS
none    /mnt/mycephfs  fuse.ceph ceph.id={user-ID}[,ceph.conf={path/to/conf.conf}],_netdev,defaults  0 0

For example:

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

ceph-fuse@.service and ceph-fuse.target 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 ceph-fuse.target
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.