Chapter 2. Understanding process management for Ceph As a storage administrator, you can manipulate the various Ceph daemons by type or instance in a Red Hat Ceph Storage cluster. Manipulating these daemons allows you to start, stop and restart all of the Ceph services as needed. 2.1. Prerequisites Installation of the Red Hat Ceph Storage software. 2.2. Ceph process management In Red Hat Ceph Storage, all process management is done through the Systemd service. Each time you want to start , restart , and stop the Ceph daemons, you must specify the daemon type or the daemon instance. Additional Resources For more information on using systemd, see Introduction to systemd chapter, and the Managing system services with systemctl chapter in the Configuring basic system settings guide for Red Hat Enterprise Linux 8. 2.3. Starting, stopping, and restarting all Ceph daemons You can start, stop, and restart all Ceph daemons as the root user from the host where you want to stop the Ceph daemons. Prerequisites A running Red Hat Ceph Storage cluster. Having root access to the node. Procedure On the host where you want to start, stop, and restart the daemons, run the systemctl service to get the SERVICE_ID of the service. Example Starting all Ceph daemons: Syntax Example Stopping all Ceph daemons: Syntax Example Restarting all Ceph daemons: Syntax Example 2.4. Starting, stopping, and restarting all Ceph services Ceph services are logical groups of Ceph daemons of the same type, configured to run in the same Red Hat Ceph Storage cluster. The orchestration layer in Ceph allows the user to manage these services in a centralized way, making it easy to execute operations that affect all the Ceph daemons that belong to the same logical service. The Ceph daemons running in each host are managed through the Systemd service. You can start, stop, and restart all Ceph services from the host where you want to manage the Ceph services. Important If you want to start,stop, or restart a specific Ceph daemon in a specific host, you need to use the SystemD service. To obtain a list of the SystemD services running in a specific host, connect to the host, and run the following command: Example The output will give you a list of the service names that you can use, to manage each Ceph daemon. Prerequisites A running Red Hat Ceph Storage cluster. Having root access to the node. Procedure Log into the Cephadm shell: Example Run the ceph orch ls command to get a list of Ceph services configured in the Red Hat Ceph Storage cluster and to get the specific service ID. Example To start a specific service, run the following command: Syntax Example To stop a specific service, run the following command: Important The ceph orch stop SERVICE_ID command results in the Red Hat Ceph Storage cluster being inaccessible, only for the MON and MGR service. It is recommended to use the systemctl stop SERVICE_ID command to stop a specific daemon in the host. Syntax Example In the example the ceph orch stop node-exporter command removes all the daemons of the node exporter service. To restart a specific service, run the following command: Syntax Example 2.5. Viewing log files of Ceph daemons that run in containers Use the journald daemon from the container host to view a log file of a Ceph daemon from a container. Prerequisites Installation of the Red Hat Ceph Storage software. Root-level access to the node. Procedure To view the entire Ceph log file, run a journalctl command as root composed in the following format: Syntax In the above example, you can view the entire log for the OSD with ID osd.8 . To show only the recent journal entries, use the -f option. Syntax Example Note You can also use the sosreport utility to view the journald logs. For more details about SOS reports, see the What is an sosreport and how to create one in Red Hat Enterprise Linux? solution on the Red Hat Customer Portal. Additional Resources The journalctl manual page. 2.6. Powering down and rebooting Red Hat Ceph Storage cluster You can power down and reboot the Red Hat Ceph Storage cluster using two different approaches: systemctl commands and the Ceph Orchestrator. You can choose either approach to power down and reboot the cluster. 2.6.1. Powering down and rebooting the cluster using the systemctl commands You can use the systemctl commands approach to power down and reboot the Red Hat Ceph Storage cluster. This approach follows the Linux way of stopping the services. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access. Procedure Powering down the Red Hat Ceph Storage cluster Stop the clients from using the Block Device images RADOS Gateway - Ceph Object Gateway on this cluster and any other clients. Log into the Cephadm shell: Example The cluster must be in healthy state ( Health_OK and all PGs active+clean ) before proceeding. Run ceph status on the host with the client keyrings, for example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy. Example If you use the Ceph File System ( CephFS ), bring down the CephFS cluster: Syntax Example Set the noout , norecover , norebalance , nobackfill , nodown , and pause flags. Run the following on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller node: Example Important The above example is only for stopping the service and each OSD in the OSD node and it needs to be repeated on each OSD node. If the MDS and Ceph Object Gateway nodes are on their own dedicated nodes, power them off. Get the systemd target of the daemons: Example Disable the target that includes the cluster FSID: Example Stop the target: Example This stops all the daemons on the host that needs to be stopped. Shutdown the node: Example Repeat the above steps for all the nodes of the cluster. Rebooting the Red Hat Ceph Storage cluster If network equipment was involved, ensure it is powered ON and stable prior to powering ON any Ceph hosts or nodes. Power ON the administration node. Enable the systemd target to get all the daemons running: Example Start the systemd target: Example Wait for all the nodes to come up. Verify all the services are up and there are no connectivity issues between the nodes. Unset the noout , norecover , norebalance , nobackfill , nodown and pause flags. Run the following on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller node: Example If you use the Ceph File System ( CephFS ), bring the CephFS cluster back up by setting the joinable flag to true : Syntax Example Verification Verify the cluster is in healthy state ( Health_OK and all PGs active+clean ). Run ceph status on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy. Example Additional Resources For more information on installing Ceph, see the Red Hat Ceph Storage Installation Guide . 2.6.2. Powering down and rebooting the cluster using the Ceph Orchestrator You can also use the capabilities of the Ceph Orchestrator to power down and reboot the Red Hat Ceph Storage cluster. In most cases, it is a single system login that can help in powering off the cluster. The Ceph Orchestrator supports several operations, such as start , stop , and restart . You can use these commands with systemctl , for some cases, in powering down or rebooting the cluster. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to the node. Procedure Powering down the Red Hat Ceph Storage cluster Stop the clients from using the user Block Device Image and Ceph Object Gateway on this cluster and any other clients. Log into the Cephadm shell: Example The cluster must be in healthy state ( Health_OK and all PGs active+clean ) before proceeding. Run ceph status on the host with the client keyrings, for example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy. Example If you use the Ceph File System ( CephFS ), bring down the CephFS cluster: Syntax Example Set the noout , norecover , norebalance , nobackfill , nodown , and pause flags. Run the following on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller node: Example Stop the MDS service. Fetch the MDS service name: Example Stop the MDS service using the fetched name in the step: Syntax Stop the Ceph Object Gateway services. Repeat for each deployed service. Fetch the Ceph Object Gateway service names: Example Stop the Ceph Object Gateway service using the fetched name: Syntax Stop the Alertmanager service: Example Stop the node-exporter service which is a part of the monitoring stack: Example Stop the Prometheus service: Example Stop the Grafana dashboard service: Example Stop the crash service: Example Shut down the OSD nodes from the cephadm node, one by one. Repeat this step for all the OSDs in the cluster. Fetch the OSD ID: Example Shut down the OSD node using the OSD ID you fetched: Example Stop the monitors one by one. Identify the hosts hosting the monitors: Example On each host, stop the monitor. Identify the systemctl unit name: Example Stop the service: Syntax Shut down all the hosts. Rebooting the Red Hat Ceph Storage cluster If network equipment was involved, ensure it is powered ON and stable prior to powering ON any Ceph hosts or nodes. Power ON all the Ceph hosts. Log into the administration node from the Cephadm shell: Example Verify all the services are in running state: Example Ensure the cluster health is `Health_OK`status: Example Unset the noout , norecover , norebalance , nobackfill , nodown and pause flags. Run the following on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller node: Example If you use the Ceph File System ( CephFS ), bring the CephFS cluster back up by setting the joinable flag to true : Syntax Example Verification Verify the cluster is in healthy state ( Health_OK and all PGs active+clean ). Run ceph status on a node with the client keyrings, for example, the Ceph Monitor or OpenStack controller nodes, to ensure the cluster is healthy. Example Additional Resources For more information on installing Ceph see the Red Hat Ceph Storage Installation Guide

Commands:
systemctl --type=service ceph-499829b4-832f-11eb-8d6d-001a4a000635@mon.host01.service
systemctl start SERVICE_ID
systemctl start ceph-499829b4-832f-11eb-8d6d-001a4a000635@mon.host01.service
systemctl stop SERVICE_ID
systemctl stop ceph-499829b4-832f-11eb-8d6d-001a4a000635@mon.host01.service
systemctl restart SERVICE_ID
systemctl restart ceph-499829b4-832f-11eb-8d6d-001a4a000635@mon.host01.service
systemctl list-units "ceph*"
cephadm shell
ceph orch ls NAME RUNNING REFRESHED AGE PLACEMENT IMAGE NAME IMAGE ID alertmanager 1/1 4m ago 4M count:1 registry.redhat.io/openshift4/ose-prometheus-alertmanager:v4.5 b7bae610cd46 crash 3/3 4m ago 4M * registry.redhat.io/rhceph-alpha/rhceph-5-rhel8:latest c88a5d60f510 grafana 1/1 4m ago 4M count:1 registry.redhat.io/rhceph-alpha/rhceph-5-dashboard-rhel8:latest bd3d7748747b mgr 2/2 4m ago 4M count:2 registry.redhat.io/rhceph-alpha/rhceph-5-rhel8:latest c88a5d60f510 mon 2/2 4m ago 10w count:2 registry.redhat.io/rhceph-alpha/rhceph-5-rhel8:latest c88a5d60f510 nfs.foo 0/1 - - count:1 <unknown> <unknown> node-exporter 1/3 4m ago 4M * registry.redhat.io/openshift4/ose-prometheus-node-exporter:v4.5 mix osd.all-available-devices 5/5 4m ago 3M * registry.redhat.io/rhceph-alpha/rhceph-5-rhel8:latest c88a5d60f510 prometheus 1/1 4m ago 4M count:1 registry.redhat.io/openshift4/ose-prometheus:v4.6 bebb0ddef7f0 rgw.test_realm.test_zone 2/2 4m ago 3M count:2 registry.redhat.io/rhceph-alpha/rhceph-5-rhel8:latest c88a5d60f510
ceph orch start SERVICE_ID
ceph orch start node-exporter
ceph orch stop SERVICE_ID
ceph orch stop node-exporter
ceph orch restart SERVICE_ID
ceph orch restart node-exporter
journalctl -u ceph SERVICE_ID
journalctl -u ceph-499829b4-832f-11eb-8d6d-001a4a000635@osd.8.service
journalctl -fu SERVICE_ID
journalctl -fu ceph-499829b4-832f-11eb-8d6d-001a4a000635@osd.8.service
cephadm shell
ceph -s
ceph fs set FS_NAME max_mds 1 ceph fs fail FS_NAME ceph status ceph fs set FS_NAME joinable false
ceph fs set cephfs max_mds 1 ceph fs fail cephfs ceph status ceph fs set cephfs joinable false
ceph osd set noout ceph osd set norecover ceph osd set norebalance ceph osd set nobackfill ceph osd set nodown ceph osd set pause
systemctl list-units --type target | grep ceph ceph-0b007564-ec48-11ee-b736-525400fd02f8.target loaded active active Ceph cluster 0b007564-ec48-11ee-b736-525400fd02f8 ceph.target loaded active active All Ceph clusters and services
systemctl disable ceph-0b007564-ec48-11ee-b736-525400fd02f8.target Removed "/etc/systemd/system/multi-user.target.wants/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target". Removed "/etc/systemd/system/ceph.target.wants/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target".
systemctl stop ceph-0b007564-ec48-11ee-b736-525400fd02f8.target
shutdown Shutdown scheduled for Wed 2024-03-27 11:47:19 EDT, use 'shutdown -c' to cancel.
systemctl enable ceph-0b007564-ec48-11ee-b736-525400fd02f8.target Created symlink /etc/systemd/system/multi-user.target.wants/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target /etc/systemd/system/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target. Created symlink /etc/systemd/system/ceph.target.wants/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target /etc/systemd/system/ceph-0b007564-ec48-11ee-b736-525400fd02f8.target.
systemctl start ceph-0b007564-ec48-11ee-b736-525400fd02f8.target
ceph osd unset noout ceph osd unset norecover ceph osd unset norebalance ceph osd unset nobackfill ceph osd unset nodown ceph osd unset pause
ceph fs set FS_NAME joinable true
ceph fs set cephfs joinable true
ceph -s
cephadm shell
ceph -s
ceph fs set FS_NAME max_mds 1 ceph fs fail FS_NAME ceph status ceph fs set FS_NAME joinable false ceph mds fail FS_NAME : N
ceph fs set cephfs max_mds 1 ceph fs fail cephfs ceph status ceph fs set cephfs joinable false ceph mds fail cephfs:1
ceph osd set noout ceph osd set norecover ceph osd set norebalance ceph osd set nobackfill ceph osd set nodown ceph osd set pause
ceph orch ls --service-type mds
ceph orch stop SERVICE-NAME
ceph orch ls --service-type rgw
ceph orch stop SERVICE-NAME
ceph orch stop alertmanager
ceph orch stop node-exporter
ceph orch stop prometheus
ceph orch stop grafana
ceph orch stop crash
ceph orch ps --daemon-type=osd
ceph orch daemon stop osd.1 Scheduled to stop osd.1 on host 'host02'
ceph orch ps --daemon-type mon
systemctl list-units ceph-* | grep mon
systemct stop SERVICE-NAME
cephadm shell
ceph orch ls
ceph -s
ceph osd unset noout ceph osd unset norecover ceph osd unset norebalance ceph osd unset nobackfill ceph osd unset nodown ceph osd unset pause
ceph fs set FS_NAME joinable true
ceph fs set cephfs joinable true
ceph -s