Chapter 3. Management of hosts using the Ceph Orchestrator As a storage administrator, you can use the Ceph Orchestrator with Cephadm in the backend to add, list, and remove hosts in an existing Red Hat Ceph Storage cluster. You can also add labels to hosts. Labels are free-form and have no specific meanings. Each host can have multiple labels. For example, apply the mon label to all hosts that have monitor daemons deployed, mgr for all hosts with manager daemons deployed, rgw for Ceph object gateways, and so on. Labeling all the hosts in the storage cluster helps to simplify system management tasks by allowing you to quickly identify the daemons running on each host. In addition, you can use the Ceph Orchestrator or a YAML file to deploy or remove daemons on hosts that have specific host labels. This section covers the following administrative tasks: Adding hosts using the Ceph Orchestrator . Adding multiple hosts using the Ceph Orchestrator . Listing hosts using the Ceph Orchestrator . Adding a label to a host . Removing a label from a host . Removing hosts using the Ceph Orchestrator . Placing hosts in the maintenance mode using the Ceph Orchestrator . Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all the nodes. The IP addresses of the new hosts should be updated in /etc/hosts file. 3.1. Adding hosts using the Ceph Orchestrator You can use the Ceph Orchestrator with Cephadm in the backend to add hosts to an existing Red Hat Ceph Storage cluster. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all nodes in the storage cluster. Register the nodes to the CDN and attach subscriptions. Ansible user with sudo and passwordless ssh access to all nodes in the storage cluster. Procedure From the Ceph administration node, log into the Cephadm shell: Example Extract the cluster's public SSH keys to a folder: Syntax Example Copy Ceph cluster's public SSH keys to the root user's authorized_keys file on the new host: Syntax Example From the Ansible administration node, add the new host to the Ansible inventory file. The default location for the file is /usr/share/cephadm-ansible/hosts . The following example shows the structure of a typical inventory file: Example Note If you have previously added the new host to the Ansible inventory file and run the preflight playbook on the host, skip to step 6. Run the preflight playbook with the --limit option: Syntax Example The preflight playbook installs podman , lvm2 , chronyd , and cephadm on the new host. After installation is complete, cephadm resides in the /usr/sbin/ directory. From the Ceph administration node, log into the Cephadm shell: Example Use the cephadm orchestrator to add hosts to the storage cluster: Syntax The --label option is optional and this adds the labels when adding the hosts. You can add multiple labels to the host. Example Verification List the hosts: Example Additional Resources See the Listing hosts using the Ceph Orchestrator section in the Red Hat Ceph Storage Operations Guide . For more information about the cephadm-preflight playbook, see Running the preflight playbook section in the Red Hat Ceph Storage Installation Guide . See the Registering Red Hat Ceph Storage nodes to the CDN and attaching subscriptions section in the Red Hat Ceph Storage Installation Guide . See the Creating an Ansible user with sudo access section in the Red Hat Ceph Storage Installation Guide . 3.2. Adding multiple hosts using the Ceph Orchestrator You can use the Ceph Orchestrator to add multiple hosts to a Red Hat Ceph Storage cluster at the same time using the service specification in YAML file format. Prerequisites A running Red Hat Ceph Storage cluster. Procedure Create the hosts.yaml file: Example Edit the hosts.yaml file to include the following details: Example Mount the YAML file under a directory in the container: Example Navigate to the directory: Example Deploy the hosts using service specification: Syntax Example Verification List the hosts: Example Additional Resources See the Listing hosts using the Ceph Orchestrator section in the Red Hat Ceph Storage Operations Guide . 3.3. Listing hosts using the Ceph Orchestrator You can list hosts of a Ceph cluster with Ceph Orchestrators. Note The STATUS of the hosts is blank, in the output of the ceph orch host ls command. Prerequisites A running Red Hat Ceph Storage cluster. Hosts are added to the storage cluster. Procedure Log into the Cephadm shell: Example List the hosts of the cluster: Example You will see that the STATUS of the hosts is blank which is expected. 3.4. Adding a label to a host Use the Ceph Orchestrator to add a label to a host. Labels can be used to specify placement of daemons. A few examples of labels are mgr , mon , and osd based on the service deployed on the hosts. Each host can have multiple labels. You can also add the following host labels that have special meaning to cephadm and they begin with _ : _no_schedule : This label prevents cephadm from scheduling or deploying daemons on the host. If it is added to an existing host that already contains Ceph daemons, it causes cephadm to move those daemons elsewhere, except OSDs which are not removed automatically. When a host is added with the _no_schedule label, no daemons are deployed on it. When the daemons are drained before the host is removed, the _no_schedule label is set on that host. _no_autotune_memory : This label does not autotune memory on the host. It prevents the daemon memory from being tuned even when the osd_memory_target_autotune option or other similar options are enabled for one or more daemons on that host. _admin : By default, the _admin label is applied to the bootstrapped host in the storage cluster and the client.admin key is set to be distributed to that host with the ceph orch client-keyring {ls|set|rm} function. Adding this label to additional hosts normally causes cephadm to deploy configuration and keyring files in the /etc/ceph directory. Prerequisites A storage cluster that has been installed and bootstrapped. Root-level access to all nodes in the storage cluster. Hosts are added to the storage cluster. Procedure Log in to the Cephadm shell: Example Add a label to a host: Syntax Example Verification List the hosts: Example 3.5. Removing a label from a host You can use the Ceph orchestrator to remove a label from a host. Prerequisites A storage cluster that has been installed and bootstrapped. Root-level access to all nodes in the storage cluster. Procedure Launch the cephadm shell: Remove the label. Syntax Example Verification List the hosts: Example 3.6. Removing hosts using the Ceph Orchestrator You can remove hosts of a Ceph cluster with the Ceph Orchestrators. All the daemons are removed with the drain option which adds the _no_schedule label to ensure that you cannot deploy any daemons or a cluster till the operation is complete. Important If you are removing the bootstrap host, be sure to copy the admin keyring and the configuration file to another host in the storage cluster before you remove the host. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all the nodes. Hosts are added to the storage cluster. All the services are deployed. Cephadm is deployed on the nodes where the services have to be removed. Procedure Log into the Cephadm shell: Example Fetch the host details: Example Drain all the daemons from the host: Syntax Example The _no_schedule label is automatically applied to the host which blocks deployment. Check the status of OSD removal: Example When no placement groups (PG) are left on the OSD, the OSD is decommissioned and removed from the storage cluster. Check if all the daemons are removed from the storage cluster: Syntax Example Remove the host: Syntax Example Additional Resources See the Adding hosts using the Ceph Orchestrator section in the Red Hat Ceph Storage Operations Guide for more information. See the Listing hosts using the Ceph Orchestrator section in the Red Hat Ceph Storage Operations Guide for more information. 3.7. Placing hosts in the maintenance mode using the Ceph Orchestrator You can use the Ceph Orchestrator to place the hosts in and out of the maintenance mode. The ceph orch host maintenance enter command stops the systemd target which causes all the Ceph daemons to stop on the host. Similarly, the ceph orch host maintenance exit command restarts the systemd target and the Ceph daemons restart on their own. The orchestrator adopts the following workflow when the host is placed in maintenance: Confirms the removal of hosts does not impact data availability by running the orch host ok-to-stop command. If the host has Ceph OSD daemons, it applies noout to the host subtree to prevent data migration from triggering during the planned maintenance slot. Stops the Ceph target, thereby, stopping all the daemons. Disables the ceph target on the host, to prevent a reboot from automatically starting Ceph services. Exiting maintenance reverses the above sequence. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all the nodes. Hosts added to the cluster. Procedure Log into the Cephadm shell: Example You can either place the host in maintenance mode or place it out of the maintenance mode: Place the host in maintenance mode: Syntax Example The --force flag allows the user to bypass warnings, but not alerts. Place the host out of the maintenance mode: Syntax Example Verification List the hosts: Example

Commands:
cephadm shell
ceph cephadm get-pub-key > ~/ PATH
ceph cephadm get-pub-key > ~/ceph.pub
ssh-copy-id -f -i ~/ PATH root@ HOST_NAME_2
ssh-copy-id -f -i ~/ceph.pub root@host02
host01 host02 host03 [admin] host00
ansible-playbook -i INVENTORY_FILE cephadm-preflight.yml --extra-vars "ceph_origin=rhcs,ceph_rhcs_version=6" --limit NEWHOST
[ceph-admin@admin cephadm-ansible]USD ansible-playbook -i hosts cephadm-preflight.yml --extra-vars "ceph_origin=rhcs,ceph_rhcs_version=6" --limit host02
cephadm shell
ceph orch host add HOST_NAME IP_ADDRESS_OF_HOST [--label= LABEL_NAME_1 , LABEL_NAME_2 ]
ceph orch host add host02 10.10.128.70 --labels=mon,mgr
ceph orch host ls
touch hosts.yaml
service_type: host addr: host01 hostname: host01 labels: - mon - osd - mgr --- service_type: host addr: host02 hostname: host02 labels: - mon - osd - mgr --- service_type: host addr: host03 hostname: host03 labels: - mon - osd
cephadm shell --mount hosts.yaml:/var/lib/ceph/hosts.yaml
cd /var/lib/ceph/
ceph orch apply -i FILE_NAME .yaml
ceph orch apply -i hosts.yaml
ceph orch host ls
cephadm shell
ceph orch host ls
cephadm shell
ceph orch host label add HOSTNAME LABEL
ceph orch host label add host02 mon
ceph orch host ls
cephadm shell
ceph orch host label rm HOSTNAME LABEL
ceph orch host label rm host02 mon
ceph orch host ls
cephadm shell
ceph orch host ls
ceph orch host drain HOSTNAME
ceph orch host drain host02
ceph orch osd rm status
ceph orch ps HOSTNAME
ceph orch ps host02
ceph orch host rm HOSTNAME
ceph orch host rm host02
cephadm shell
ceph orch host maintenance enter HOST_NAME [--force]
ceph orch host maintenance enter host02 --force
ceph orch host maintenance exit HOST_NAME
ceph orch host maintenance exit host02
ceph orch host ls