Cephadm Operations

Watching cephadm log messages

Cephadm writes logs to the cephadm cluster log channel. You can monitor Ceph’s activity in real time by reading the logs as they fill up. Run the following command to see the logs in real time:

ceph -W cephadm

By default, this command shows info-level events and above. To see debug-level messages as well as info-level events, run the following commands:

ceph config set mgr mgr/cephadm/log_to_cluster_level debug
ceph -W cephadm --watch-debug

Warning

The debug messages are very verbose!

You can see recent events by running the following command:

ceph log last cephadm

These events are also logged to the ceph.cephadm.log file on monitor hosts as well as to the monitor daemons’ stderr.

Ceph daemon control

Starting and stopping daemons

You can stop, start, or restart a daemon with:

ceph orch daemon stop <name>
ceph orch daemon start <name>
ceph orch daemon restart <name>

You can also do the same for all daemons for a service with:

ceph orch stop <name>
ceph orch start <name>
ceph orch restart <name>

Redeploying or reconfiguring a daemon

The container for a daemon can be stopped, recreated, and restarted with the redeploy command:

ceph orch daemon redeploy <name> [--image <image>]

A container image name can optionally be provided to force a particular image to be used (instead of the image specified by the container_image config value).

If only the ceph configuration needs to be regenerated, you can also issue a reconfig command, which will rewrite the ceph.conf file but will not trigger a restart of the daemon.

ceph orch daemon reconfig <name>

Rotating a daemon’s authenticate key

All Ceph and gateway daemons in the cluster have a secret key that is used to connect to and authenticate with the cluster. This key can be rotated (i.e., replaced with a new key) with the following command:

ceph orch daemon rotate-key <name>

For MDS, OSD, and MGR daemons, this does not require a daemon restart. For other daemons, however (e.g., RGW), the daemon may be restarted to switch to the new key.

Ceph daemon logs

Logging to journald

Ceph daemons traditionally write logs to /var/log/ceph. Ceph daemons log to journald by default and Ceph logs are captured by the container runtime environment. They are accessible via journalctl.

Note

Prior to Quincy, ceph daemons logged to stderr.

Example of logging to journald

For example, to view the logs for the daemon mon.foo for a cluster with ID 5c5a50ae-272a-455d-99e9-32c6a013e694, the command would be something like:

journalctl -u ceph-5c5a50ae-272a-455d-99e9-32c6a013e694@mon.foo

This works well for normal operations when logging levels are low.

Logging to files

You can also configure Ceph daemons to log to files instead of to journald if you prefer logs to appear in files (as they did in earlier, pre-cephadm, pre-Octopus versions of Ceph). When Ceph logs to files, the logs appear in /var/log/ceph/<cluster-fsid>. If you choose to configure Ceph to log to files instead of to journald, remember to configure Ceph so that it will not log to journald (the commands for this are covered below).

Enabling logging to files

To enable logging to files, run the following commands:

ceph config set global log_to_file true
ceph config set global mon_cluster_log_to_file true

Disabling logging to journald

If you choose to log to files, we recommend disabling logging to journald or else everything will be logged twice. Run the following commands to disable logging to stderr:

ceph config set global log_to_stderr false
ceph config set global mon_cluster_log_to_stderr false
ceph config set global log_to_journald false
ceph config set global mon_cluster_log_to_journald false

Note

You can change the default by passing –log-to-file during bootstrapping a new cluster.

Modifying the log retention schedule

By default, cephadm sets up log rotation on each host to rotate these files. You can configure the logging retention schedule by modifying /etc/logrotate.d/ceph.<cluster-fsid>.

Data location

Cephadm stores daemon data and logs in different locations than did older, pre-cephadm (pre Octopus) versions of ceph:

  • /var/log/ceph/<cluster-fsid> contains all cluster logs. By default, cephadm logs via stderr and the container runtime. These logs will not exist unless you have enabled logging to files as described in cephadm-logs.

  • /var/lib/ceph/<cluster-fsid> contains all cluster daemon data (besides logs).

  • /var/lib/ceph/<cluster-fsid>/<daemon-name> contains all data for an individual daemon.

  • /var/lib/ceph/<cluster-fsid>/crash contains crash reports for the cluster.

  • /var/lib/ceph/<cluster-fsid>/removed contains old daemon data directories for stateful daemons (e.g., monitor, prometheus) that have been removed by cephadm.

Disk usage

Because a few Ceph daemons (notably, the monitors and prometheus) store a large amount of data in /var/lib/ceph , we recommend moving this directory to its own disk, partition, or logical volume so that it does not fill up the root file system.

Health checks

The cephadm module provides additional health checks to supplement the default health checks provided by the Cluster. These additional health checks fall into two categories:

  • cephadm operations: Health checks in this category are always executed when the cephadm module is active.

  • cluster configuration: These health checks are optional, and focus on the configuration of the hosts in the cluster.

CEPHADM Operations

CEPHADM_PAUSED

This indicates that cephadm background work has been paused with ceph orch pause. Cephadm continues to perform passive monitoring activities (like checking host and daemon status), but it will not make any changes (like deploying or removing daemons).

Resume cephadm work by running the following command:

ceph orch resume

CEPHADM_STRAY_HOST

This indicates that one or more hosts have Ceph daemons that are running, but are not registered as hosts managed by cephadm. This means that those services cannot currently be managed by cephadm (e.g., restarted, upgraded, included in ceph orch ps).

  • You can manage the host(s) by running the following command:

    ceph orch host add *<hostname>*

    Note

    You might need to configure SSH access to the remote host before this will work.

  • See Fully qualified domain names vs bare host names for more information about host names and domain names.

  • Alternatively, you can manually connect to the host and ensure that services on that host are removed or migrated to a host that is managed by cephadm.

  • This warning can be disabled entirely by running the following command:

    ceph config set mgr mgr/cephadm/warn_on_stray_hosts false

CEPHADM_STRAY_DAEMON

One or more Ceph daemons are running but not are not managed by cephadm. This may be because they were deployed using a different tool, or because they were started manually. Those services cannot currently be managed by cephadm (e.g., restarted, upgraded, or included in ceph orch ps).

  • If the daemon is a stateful one (monitor or OSD), it should be adopted by cephadm; see Converting an existing cluster to cephadm. For stateless daemons, it is usually easiest to provision a new daemon with the ceph orch apply command and then stop the unmanaged daemon.

  • If the stray daemon(s) are running on hosts not managed by cephadm, you can manage the host(s) by running the following command:

    ceph orch host add *<hostname>*

    Note

    You might need to configure SSH access to the remote host before this will work.

  • See Fully qualified domain names vs bare host names for more information about host names and domain names.

  • This warning can be disabled entirely by running the following command:

    ceph config set mgr mgr/cephadm/warn_on_stray_daemons false

CEPHADM_HOST_CHECK_FAILED

One or more hosts have failed the basic cephadm host check, which verifies that (1) the host is reachable and cephadm can be executed there, and (2) that the host satisfies basic prerequisites, like a working container runtime (podman or docker) and working time synchronization. If this test fails, cephadm will no be able to manage services on that host.

You can manually run this check by running the following command:

ceph cephadm check-host *<hostname>*

You can remove a broken host from management by running the following command:

ceph orch host rm *<hostname>*

You can disable this health warning by running the following command:

ceph config set mgr mgr/cephadm/warn_on_failed_host_check false

Cluster Configuration Checks

Cephadm periodically scans each of the hosts in the cluster in order to understand the state of the OS, disks, NICs etc. These facts can then be analysed for consistency across the hosts in the cluster to identify any configuration anomalies.

Enabling Cluster Configuration Checks

The configuration checks are an optional feature, and are enabled by running the following command:

ceph config set mgr mgr/cephadm/config_checks_enabled true

States Returned by Cluster Configuration Checks

The configuration checks are triggered after each host scan (1m). The cephadm log entries will show the current state and outcome of the configuration checks as follows:

Disabled state (config_checks_enabled false):

ALL cephadm checks are disabled, use 'ceph config set mgr mgr/cephadm/config_checks_enabled true' to enable

Enabled state (config_checks_enabled true):

CEPHADM 8/8 checks enabled and executed (0 bypassed, 0 disabled). No issues detected

Managing Configuration Checks (subcommands)

The configuration checks themselves are managed through several cephadm subcommands.

To determine whether the configuration checks are enabled, run the following command:

ceph cephadm config-check status

This command returns the status of the configuration checker as either “Enabled” or “Disabled”.

To list all the configuration checks and their current states, run the following command:

# ceph cephadm config-check ls

  NAME             HEALTHCHECK                      STATUS   DESCRIPTION
kernel_security  CEPHADM_CHECK_KERNEL_LSM         enabled  checks SELINUX/Apparmor profiles are consistent across cluster hosts
os_subscription  CEPHADM_CHECK_SUBSCRIPTION       enabled  checks subscription states are consistent for all cluster hosts
public_network   CEPHADM_CHECK_PUBLIC_MEMBERSHIP  enabled  check that all hosts have a NIC on the Ceph public_network
osd_mtu_size     CEPHADM_CHECK_MTU                enabled  check that OSD hosts share a common MTU setting
osd_linkspeed    CEPHADM_CHECK_LINKSPEED          enabled  check that OSD hosts share a common linkspeed
network_missing  CEPHADM_CHECK_NETWORK_MISSING    enabled  checks that the cluster/public networks defined exist on the Ceph hosts
ceph_release     CEPHADM_CHECK_CEPH_RELEASE       enabled  check for Ceph version consistency - ceph daemons should be on the same release (unless upgrade is active)
kernel_version   CEPHADM_CHECK_KERNEL_VERSION     enabled  checks that the MAJ.MIN of the kernel on Ceph hosts is consistent

The name of each configuration check can be used to enable or disable a specific check by running a command of the following form: :

ceph cephadm config-check disable <name>

For example:

ceph cephadm config-check disable kernel_security

CEPHADM_CHECK_KERNEL_LSM

Each host within the cluster is expected to operate within the same Linux Security Module (LSM) state. For example, if the majority of the hosts are running with SELINUX in enforcing mode, any host not running in this mode is flagged as an anomaly and a healtcheck (WARNING) state raised.

CEPHADM_CHECK_SUBSCRIPTION

This check relates to the status of vendor subscription. This check is performed only for hosts using RHEL, but helps to confirm that all hosts are covered by an active subscription, which ensures that patches and updates are available.

CEPHADM_CHECK_PUBLIC_MEMBERSHIP

All members of the cluster should have NICs configured on at least one of the public network subnets. Hosts that are not on the public network will rely on routing, which may affect performance.

CEPHADM_CHECK_MTU

The MTU of the NICs on OSDs can be a key factor in consistent performance. This check examines hosts that are running OSD services to ensure that the MTU is configured consistently within the cluster. This is determined by establishing the MTU setting that the majority of hosts is using. Any anomalies result in a Ceph health check.

CEPHADM_CHECK_LINKSPEED

This check is similar to the MTU check. Linkspeed consistency is a factor in consistent cluster performance, just as the MTU of the NICs on the OSDs is. This check determines the linkspeed shared by the majority of OSD hosts, and a health check is run for any hosts that are set at a lower linkspeed rate.

CEPHADM_CHECK_NETWORK_MISSING

The public_network and cluster_network settings support subnet definitions for IPv4 and IPv6. If these settings are not found on any host in the cluster, a health check is raised.

CEPHADM_CHECK_CEPH_RELEASE

Under normal operations, the Ceph cluster runs daemons under the same ceph release (that is, the Ceph cluster runs all daemons under (for example) Octopus). This check determines the active release for each daemon, and reports any anomalies as a healthcheck. This check is bypassed if an upgrade process is active within the cluster.

CEPHADM_CHECK_KERNEL_VERSION

The OS kernel version (maj.min) is checked for consistency across the hosts. The kernel version of the majority of the hosts is used as the basis for identifying anomalies.

Client keyrings and configs

Cephadm can distribute copies of the ceph.conf file and client keyring files to hosts. Starting from versions 16.2.10 (Pacific) and 17.2.1 (Quincy), in addition to the default location /etc/ceph/ cephadm also stores config and keyring files in the /var/lib/ceph/<fsid>/config directory. It is usually a good idea to store a copy of the config and client.admin keyring on any host used to administer the cluster via the CLI. By default, cephadm does this for any nodes that have the _admin label (which normally includes the bootstrap host).

Note

Ceph daemons will still use files on /etc/ceph/. The new configuration location /var/lib/ceph/<fsid>/config is used by cephadm only. Having this config directory under the fsid helps cephadm to load the configuration associated with the cluster.

When a client keyring is placed under management, cephadm will:

  • build a list of target hosts based on the specified placement spec (see Daemon Placement)

  • store a copy of the /etc/ceph/ceph.conf file on the specified host(s)

  • store a copy of the ceph.conf file at /var/lib/ceph/<fsid>/config/ceph.conf on the specified host(s)

  • store a copy of the ceph.client.admin.keyring file at /var/lib/ceph/<fsid>/config/ceph.client.admin.keyring on the specified host(s)

  • store a copy of the keyring file on the specified host(s)

  • update the ceph.conf file as needed (e.g., due to a change in the cluster monitors)

  • update the keyring file if the entity’s key is changed (e.g., via ceph auth ... commands)

  • ensure that the keyring file has the specified ownership and specified mode

  • remove the keyring file when client keyring management is disabled

  • remove the keyring file from old hosts if the keyring placement spec is updated (as needed)

Listing Client Keyrings

To see the list of client keyrings are currently under management, run the following command:

ceph orch client-keyring ls

Putting a Keyring Under Management

To put a keyring under management, run a command of the following form:

ceph orch client-keyring set <entity> <placement> [--mode=<mode>] [--owner=<uid>.<gid>] [--path=<path>]

  • By default, the path is /etc/ceph/client.{entity}.keyring, which is where Ceph looks by default. Be careful when specifying alternate locations, as existing files may be overwritten.

  • A placement of * (all hosts) is common.

  • The mode defaults to 0600 and ownership to 0:0 (user root, group root).

For example, to create a client.rbd key and deploy it to hosts with the rbd-client label and make it group readable by uid/gid 107 (qemu), run the following commands:

ceph auth get-or-create-key client.rbd mon 'profile rbd' mgr 'profile rbd' osd 'profile rbd pool=my_rbd_pool'
ceph orch client-keyring set client.rbd label:rbd-client --owner 107:107 --mode 640

The resulting keyring file is:

-rw-r-----. 1 qemu qemu 156 Apr 21 08:47 /etc/ceph/client.client.rbd.keyring

Disabling Management of a Keyring File

To disable management of a keyring file, run a command of the following form:

ceph orch client-keyring rm <entity>

Note

This deletes any keyring files for this entity that were previously written to cluster nodes.

/etc/ceph/ceph.conf

Distributing ceph.conf to hosts that have no keyrings

It might be useful to distribute ceph.conf files to hosts without an associated client keyring file. By default, cephadm deploys only a ceph.conf file to hosts where a client keyring is also distributed (see above). To write config files to hosts without client keyrings, run the following command:

ceph config set mgr mgr/cephadm/manage_etc_ceph_ceph_conf true

Using Placement Specs to specify which hosts get keyrings

By default, the configs are written to all hosts (i.e., those listed by ceph orch host ls). To specify which hosts get a ceph.conf, run a command of the following form:

ceph config set mgr mgr/cephadm/manage_etc_ceph_ceph_conf_hosts <placement spec>

For example, to distribute configs to hosts with the bare_config label, run the following command:

Distributing ceph.conf to hosts tagged with bare_config

For example, to distribute configs to hosts with the bare_config label, run the following command:

ceph config set mgr mgr/cephadm/manage_etc_ceph_ceph_conf_hosts label:bare_config

(See Daemon Placement for more information about placement specs.)

Purging a cluster

Danger

THIS OPERATION WILL DESTROY ALL DATA STORED IN THIS CLUSTER

In order to destroy a cluster and delete all data stored in this cluster, disable cephadm to stop all orchestration operations (so we avoid deploying new daemons).

ceph mgr module disable cephadm

Then verify the FSID of the cluster:

ceph fsid

Purge ceph daemons from all hosts in the cluster

# For each host:
cephadm rm-cluster --force --zap-osds --fsid <fsid>