This document is for a development version of Ceph.

Manual Deployment

All Ceph clusters require at least one monitor, and at least as many OSDs as copies of an object stored on the cluster. Bootstrapping the initial monitor(s) is the first step in deploying a Ceph Storage Cluster. Monitor deployment also sets important criteria for the entire cluster, such as the number of replicas for pools, the number of placement groups per OSD, the heartbeat intervals, whether authentication is required, etc. Most of these values are set by default, so it’s useful to know about them when setting up your cluster for production.

We will set up a cluster with mon-node1 as the monitor node, and osd-node1 and osd-node2 for OSD nodes.

Monitor Bootstrapping

Bootstrapping a monitor (a Ceph Storage Cluster, in theory) requires a number of things:

  • Unique Identifier: The fsid is a unique identifier for the cluster, and stands for File System ID from the days when the Ceph Storage Cluster was principally for the Ceph File System. Ceph now supports native interfaces, block devices, and object storage gateway interfaces too, so fsid is a bit of a misnomer.

  • Cluster Name: Ceph clusters have a cluster name, which is a simple string without spaces. The default cluster name is ceph, but you may specify a different cluster name. Overriding the default cluster name is especially useful when you are working with multiple clusters and you need to clearly understand which cluster your are working with.

    For example, when you run multiple clusters in a multisite configuration, the cluster name (e.g., us-west, us-east) identifies the cluster for the current CLI session. Note: To identify the cluster name on the command line interface, specify the Ceph configuration file with the cluster name (e.g., ceph.conf, us-west.conf, us-east.conf, etc.). Also see CLI usage (ceph --cluster {cluster-name}).

  • Monitor Name: Each monitor instance within a cluster has a unique name. In common practice, the Ceph Monitor name is the host name (we recommend one Ceph Monitor per host, and no commingling of Ceph OSD Daemons with Ceph Monitors). You may retrieve the short hostname with hostname -s.

  • Monitor Map: Bootstrapping the initial monitor(s) requires you to generate a monitor map. The monitor map requires the fsid, the cluster name (or uses the default), and at least one host name and its IP address.

  • Monitor Keyring: Monitors communicate with each other via a secret key. You must generate a keyring with a monitor secret and provide it when bootstrapping the initial monitor(s).

  • Administrator Keyring: To use the ceph CLI tools, you must have a client.admin user. So you must generate the admin user and keyring, and you must also add the client.admin user to the monitor keyring.

The foregoing requirements do not imply the creation of a Ceph Configuration file. However, as a best practice, we recommend creating a Ceph configuration file and populating it with the fsid, the mon initial members and the mon host settings.

You can get and set all of the monitor settings at runtime as well. However, a Ceph Configuration file may contain only those settings that override the default values. When you add settings to a Ceph configuration file, these settings override the default settings. Maintaining those settings in a Ceph configuration file makes it easier to maintain your cluster.

The procedure is as follows:

  1. Log in to the initial monitor node(s):

    ssh {hostname}

    For example:

    ssh mon-node1
  2. Ensure you have a directory for the Ceph configuration file. By default, Ceph uses /etc/ceph. When you install ceph, the installer will create the /etc/ceph directory automatically.

    ls /etc/ceph
  3. Create a Ceph configuration file. By default, Ceph uses ceph.conf, where ceph reflects the cluster name. Add a line containing “[global]” to the configuration file.

    sudo vim /etc/ceph/ceph.conf
  4. Generate a unique ID (i.e., fsid) for your cluster.

  5. Add the unique ID to your Ceph configuration file.

    fsid = {UUID}

    For example:

    fsid = a7f64266-0894-4f1e-a635-d0aeaca0e993
  6. Add the initial monitor(s) to your Ceph configuration file.

    mon_initial_members = {hostname}[,{hostname}]

    For example:

    mon_initial_members = mon-node1
  7. Add the IP address(es) of the initial monitor(s) to your Ceph configuration file and save the file.

    mon_host = {ip-address}[,{ip-address}]

    For example:

    mon_host =

    Note: You may use IPv6 addresses instead of IPv4 addresses, but you must set ms_bind_ipv6 to true. See Network Configuration Reference for details about network configuration.

  8. Create a keyring for your cluster and generate a monitor secret key.

    sudo ceph-authtool --create-keyring /tmp/ceph.mon.keyring --gen-key -n mon. --cap mon 'allow *'
  9. Generate an administrator keyring, generate a client.admin user and add the user to the keyring.

    sudo ceph-authtool --create-keyring /etc/ceph/ceph.client.admin.keyring --gen-key -n client.admin --cap mon 'allow *' --cap osd 'allow *' --cap mds 'allow *' --cap mgr 'allow *'
  10. Generate a bootstrap-osd keyring, generate a client.bootstrap-osd user and add the user to the keyring.

    sudo ceph-authtool --create-keyring /var/lib/ceph/bootstrap-osd/ceph.keyring --gen-key -n client.bootstrap-osd --cap mon 'profile bootstrap-osd' --cap mgr 'allow r'
  11. Add the generated keys to the ceph.mon.keyring.

    sudo ceph-authtool /tmp/ceph.mon.keyring --import-keyring /etc/ceph/ceph.client.admin.keyring
    sudo ceph-authtool /tmp/ceph.mon.keyring --import-keyring /var/lib/ceph/bootstrap-osd/ceph.keyring
  12. Change the owner for ceph.mon.keyring.

    sudo chown ceph:ceph /tmp/ceph.mon.keyring
  13. Generate a monitor map using the hostname(s), host IP address(es) and the FSID. Save it as /tmp/monmap:

    monmaptool --create --add {hostname} {ip-address} --fsid {uuid} /tmp/monmap

    For example:

    monmaptool --create --add mon-node1 --fsid a7f64266-0894-4f1e-a635-d0aeaca0e993 /tmp/monmap
  14. Create a default data directory (or directories) on the monitor host(s).

    sudo mkdir /var/lib/ceph/mon/{cluster-name}-{hostname}

    For example:

    sudo -u ceph mkdir /var/lib/ceph/mon/ceph-mon-node1

    See Monitor Config Reference - Data for details.

  15. Populate the monitor daemon(s) with the monitor map and keyring.

    sudo -u ceph ceph-mon [--cluster {cluster-name}] --mkfs -i {hostname} --monmap /tmp/monmap --keyring /tmp/ceph.mon.keyring

    For example:

    sudo -u ceph ceph-mon --mkfs -i mon-node1 --monmap /tmp/monmap --keyring /tmp/ceph.mon.keyring
  16. Consider settings for a Ceph configuration file. Common settings include the following:

    fsid = {cluster-id}
    mon_initial_members = {hostname}[, {hostname}]
    mon_host = {ip-address}[, {ip-address}]
    public_network = {network}[, {network}]
    cluster_network = {network}[, {network}]
    auth_cluster required = cephx
    auth_service required = cephx
    auth_client required = cephx
    osd_pool_default_size = {n}  # Write an object n times.
    osd_pool_default_min_size = {n} # Allow writing n copies in a degraded state.
    osd_pool_default_pg_num = {n}
    osd_crush_chooseleaf_type = {n}

    In the foregoing example, the [global] section of the configuration might look like this:

    fsid = a7f64266-0894-4f1e-a635-d0aeaca0e993
    mon_initial_members = mon-node1
    mon_host =
    public_network =
    auth_cluster_required = cephx
    auth_service_required = cephx
    auth_client_required = cephx
    osd_pool_default_size = 3
    osd_pool_default_min_size = 2
    osd_pool_default_pg_num = 333
    osd_crush_chooseleaf_type = 1
  17. Start the monitor(s).

    Start the service with systemd:

    sudo systemctl start ceph-mon@mon-node1
  18. Ensure to open firewall ports for ceph-mon.

    Open the ports with firewalld:

    sudo firewall-cmd --zone=public --add-service=ceph-mon
    sudo firewall-cmd --zone=public --add-service=ceph-mon --permanent
  19. Verify that the monitor is running.

    sudo ceph -s

    You should see output that the monitor you started is up and running, and you should see a health error indicating that placement groups are stuck inactive. It should look something like this:

      id:     a7f64266-0894-4f1e-a635-d0aeaca0e993
      health: HEALTH_OK
      mon: 1 daemons, quorum mon-node1
      mgr: mon-node1(active)
      osd: 0 osds: 0 up, 0 in
      pools:   0 pools, 0 pgs
      objects: 0 objects, 0 bytes
      usage:   0 kB used, 0 kB / 0 kB avail

    Note: Once you add OSDs and start them, the placement group health errors should disappear. See Adding OSDs for details.

Manager daemon configuration

On each node where you run a ceph-mon daemon, you should also set up a ceph-mgr daemon.

See ceph-mgr administrator’s guide

Adding OSDs

Once you have your initial monitor(s) running, you should add OSDs. Your cluster cannot reach an active + clean state until you have enough OSDs to handle the number of copies of an object (e.g., osd_pool_default_size = 2 requires at least two OSDs). After bootstrapping your monitor, your cluster has a default CRUSH map; however, the CRUSH map doesn’t have any Ceph OSD Daemons mapped to a Ceph Node.

Short Form

Ceph provides the ceph-volume utility, which can prepare a logical volume, disk, or partition for use with Ceph. The ceph-volume utility creates the OSD ID by incrementing the index. Additionally, ceph-volume will add the new OSD to the CRUSH map under the host for you. Execute ceph-volume -h for CLI details. The ceph-volume utility automates the steps of the Long Form below. To create the first two OSDs with the short form procedure, execute the following for each OSD:

  1. Create the OSD.

    copy /var/lib/ceph/bootstrap-osd/ceph.keyring from monitor node (mon-node1) to /var/lib/ceph/bootstrap-osd/ceph.keyring on osd node (osd-node1)
    ssh {osd node}
    sudo ceph-volume lvm create --data {data-path}

    For example:

    scp -3 root@mon-node1:/var/lib/ceph/bootstrap-osd/ceph.keyring root@osd-node1:/var/lib/ceph/bootstrap-osd/ceph.keyring
    ssh osd-node1
    sudo ceph-volume lvm create --data /dev/hdd1

Alternatively, the creation process can be split in two phases (prepare, and activate):

  1. Prepare the OSD.

    ssh {osd node}
    sudo ceph-volume lvm prepare --data {data-path} {data-path}

    For example:

    ssh osd-node1
    sudo ceph-volume lvm prepare --data /dev/hdd1

    Once prepared, the ID and FSID of the prepared OSD are required for activation. These can be obtained by listing OSDs in the current server:

    sudo ceph-volume lvm list
  2. Activate the OSD:

    sudo ceph-volume lvm activate {ID} {FSID}

    For example:

    sudo ceph-volume lvm activate 0 a7f64266-0894-4f1e-a635-d0aeaca0e993

Long Form

Without the benefit of any helper utilities, create an OSD and add it to the cluster and CRUSH map with the following procedure. To create the first two OSDs with the long form procedure, execute the following steps for each OSD.


This procedure does not describe deployment on top of dm-crypt making use of the dm-crypt ‘lockbox’.

  1. Connect to the OSD host and become root.

    ssh {node-name}
    sudo bash
  2. Generate a UUID for the OSD.

  3. Generate a cephx key for the OSD.

    OSD_SECRET=$(ceph-authtool --gen-print-key)
  4. Create the OSD. Note that an OSD ID can be provided as an additional argument to ceph osd new if you need to reuse a previously-destroyed OSD id. We assume that the client.bootstrap-osd key is present on the machine. You may alternatively execute this command as client.admin on a different host where that key is present.:

    ID=$(echo "{\"cephx_secret\": \"$OSD_SECRET\"}" | \
       ceph osd new $UUID -i - \
       -n client.bootstrap-osd -k /var/lib/ceph/bootstrap-osd/ceph.keyring)

    It is also possible to include a crush_device_class property in the JSON to set an initial class other than the default (ssd or hdd based on the auto-detected device type).

  5. Create the default directory on your new OSD.

    mkdir /var/lib/ceph/osd/ceph-$ID
  6. If the OSD is for a drive other than the OS drive, prepare it for use with Ceph, and mount it to the directory you just created.

    mkfs.xfs /dev/{DEV}
    mount /dev/{DEV} /var/lib/ceph/osd/ceph-$ID
  7. Write the secret to the OSD keyring file.

    ceph-authtool --create-keyring /var/lib/ceph/osd/ceph-$ID/keyring \
         --name osd.$ID --add-key $OSD_SECRET
  8. Initialize the OSD data directory.

    ceph-osd -i $ID --mkfs --osd-uuid $UUID
  9. Fix ownership.

    chown -R ceph:ceph /var/lib/ceph/osd/ceph-$ID
  10. After you add an OSD to Ceph, the OSD is in your configuration. However, it is not yet running. You must start your new OSD before it can begin receiving data.

    For modern systemd distributions:

    systemctl enable ceph-osd@$ID
    systemctl start ceph-osd@$ID

    For example:

    systemctl enable ceph-osd@12
    systemctl start ceph-osd@12

Adding MDS

In the below instructions, {id} is an arbitrary name, such as the hostname of the machine.

  1. Create the mds data directory.:

    mkdir -p /var/lib/ceph/mds/{cluster-name}-{id}
  2. Create a keyring.:

    ceph-authtool --create-keyring /var/lib/ceph/mds/{cluster-name}-{id}/keyring --gen-key -n mds.{id}
  3. Import the keyring and set caps.:

    ceph auth add mds.{id} osd "allow rwx" mds "allow *" mon "allow profile mds" -i /var/lib/ceph/mds/{cluster}-{id}/keyring
  4. Add to ceph.conf.:

    host = {id}
  5. Start the daemon the manual way.:

    ceph-mds --cluster {cluster-name} -i {id} -m {mon-hostname}:{mon-port} [-f]
  6. Start the daemon the right way (using ceph.conf entry).:

    service ceph start
  7. If starting the daemon fails with this error:

    mds.-1.0 ERROR: failed to authenticate: (22) Invalid argument

    Then make sure you do not have a keyring set in ceph.conf in the global section; move it to the client section; or add a keyring setting specific to this mds daemon. And verify that you see the same key in the mds data directory and ceph auth get mds.{id} output.

  8. Now you are ready to create a Ceph file system.

Manually Installing RADOSGW

For a more involved discussion of the procedure presented here, see this thread on the ceph-users mailing list.

  1. Install radosgw packages on the nodes that will be the RGW nodes.

  2. From a monitor or from a node with admin privileges, run a command of the following form:

    ceph auth get-or-create client.short-hostname-of-rgw mon 'allow rw' osd 'allow rwx'
  3. On one of the RGW nodes, do the following:

    1. Create a ceph-user-owned directory. For example:

      install -d -o ceph -g ceph /var/lib/ceph/radosgw/ceph-$(hostname -s)
    2. Enter the directory just created and create a keyring file:

      touch /var/lib/ceph/radosgw/ceph-$(hostname -s)/keyring

      Use a command similar to this one to put the key from the earlier ceph auth get-or-create step in the keyring file. Use your preferred editor:

      $EDITOR /var/lib/ceph/radosgw/ceph-$(hostname -s)/keyring
    3. Repeat these steps on every RGW node.

  4. Start the RADOSGW service by running the following command:

    systemctl start ceph-radosgw@$(hostname -s).service


Once you have your monitor and two OSDs up and running, you can watch the placement groups peer by executing the following:

ceph -w

To view the tree, execute the following:

ceph osd tree

You should see output that looks something like this:

# id    weight  type name       up/down reweight
-1      2       root default
-2      2               host osd-node1
0       1                       osd.0   up      1
-3      1               host osd-node2
1       1                       osd.1   up      1

To add (or remove) additional monitors, see Add/Remove Monitors. To add (or remove) additional Ceph OSD Daemons, see Add/Remove OSDs.

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