Cephadm Operations

Watching cephadm log messages

Cephadm logs to the cephadm cluster log channel, meaning you can monitor progress in realtime with:

# ceph -W cephadm

By default it will show info-level events and above. To see debug-level messages too:

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

Be careful: the debug messages are very verbose!

You can see recent events with:

# ceph log last cephadm

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

Ceph daemon logs

Logging to stdout

Traditionally, Ceph daemons have logged to /var/log/ceph. By default, cephadm daemons log to stderr and the logs are captured by the container runtime environment. For most systems, by default, these logs are sent to journald and accessible via journalctl.

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.

To disable logging to stderr:

ceph config set global log_to_stderr false
ceph config set global mon_cluster_log_to_stderr false

Logging to files

You can also configure Ceph daemons to log to files instead of stderr, just like they have in the past. When logging to files, Ceph logs appear in /var/log/ceph/<cluster-fsid>.

To enable logging to files:

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

We recommend disabling logging to stderr (see above) or else everything will be logged twice:

ceph config set global log_to_stderr false
ceph config set global mon_cluster_log_to_stderr false

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 daemon data and logs in slightly different locations than older versions of ceph:

  • /var/log/ceph/<cluster-fsid> contains all cluster logs. Note that by default cephadm logs via stderr and the container runtime, so these logs are normally not present.

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

SSH Configuration

Cephadm uses SSH to connect to remote hosts. SSH uses a key to authenticate with those hosts in a secure way.

Default behavior

Cephadm stores an SSH key in the monitor that is used to connect to remote hosts. When the cluster is bootstrapped, this SSH key is generated automatically and no additional configuration is necessary.

A new SSH key can be generated with:

ceph cephadm generate-key

The public portion of the SSH key can be retrieved with:

ceph cephadm get-pub-key

The currently stored SSH key can be deleted with:

ceph cephadm clear-key

You can make use of an existing key by directly importing it with:

ceph config-key set mgr/cephadm/ssh_identity_key -i <key>
ceph config-key set mgr/cephadm/ssh_identity_pub -i <pub>

You will then need to restart the mgr daemon to reload the configuration with:

ceph mgr fail

Configuring a different SSH user

Cephadm must be able to log into all the Ceph cluster nodes as an user that has enough privileges to download container images, start containers and execute commands without prompting for a password. If you do not want to use the “root” user (default option in cephadm), you must provide cephadm the name of the user that is going to be used to perform all the cephadm operations. Use the command:

ceph cephadm set-user <user>

Prior to running this the cluster ssh key needs to be added to this users authorized_keys file and non-root users must have passwordless sudo access.

Customizing the SSH configuration

Cephadm generates an appropriate ssh_config file that is used for connecting to remote hosts. This configuration looks something like this:

Host *
User root
StrictHostKeyChecking no
UserKnownHostsFile /dev/null

There are two ways to customize this configuration for your environment:

  1. Import a customized configuration file that will be stored by the monitor with:

    ceph cephadm set-ssh-config -i <ssh_config_file>

    To remove a customized SSH config and revert back to the default behavior:

    ceph cephadm clear-ssh-config
  2. You can configure a file location for the SSH configuration file with:

    ceph config set mgr mgr/cephadm/ssh_config_file <path>

    We do not recommend this approach. The path name must be visible to any mgr daemon, and cephadm runs all daemons as containers. That means that the file either need to be placed inside a customized container image for your deployment, or manually distributed to the mgr data directory (/var/lib/ceph/<cluster-fsid>/mgr.<id> on the host, visible at /var/lib/ceph/mgr/ceph-<id> from inside the container).

Health checks


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 with:

ceph orch resume


One or more hosts have running Ceph daemons 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) with:

ceph orch host add *<hostname>*

Note that you may need to configure SSH access to the remote host before this will work.

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.

You can also disable this warning entirely with:

ceph config set mgr mgr/cephadm/warn_on_stray_hosts false

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


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.

This warning can be disabled entirely with:

ceph config set mgr mgr/cephadm/warn_on_stray_daemons false


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 with:

ceph cephadm check-host *<hostname>*

You can remove a broken host from management with:

ceph orch host rm *<hostname>*

You can disable this health warning with:

ceph config set mgr mgr/cephadm/warn_on_failed_host_check false


Cephadm uses a minimized ceph.conf that only contains a minimal set of information to connect to the Ceph cluster.

To update the configuration settings, use:

ceph config set ...

To set up an initial configuration before calling bootstrap, create an initial ceph.conf file. For example:

cat <<EOF > /etc/ceph/ceph.conf
osd crush chooseleaf type = 0
cephadm bootstrap -c /root/ceph.conf ...