Ceph daemon logs

You can view the Ceph daemon logs through stderr or files.

Logging to stderr directory

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 through the journalctl command.

For example, to view the logs for the daemon on host01 for a storage cluster with ID 5c5a50ae-272a-455d-99e9-32c6a013e694:
```
[ceph: root@host01 /]# journalctl -u ceph-5c5a50ae-272a-455d-99e9-32c6a013e694@host01
```

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

To disable logging to stderr, set the following values:

[ceph: root@host01 /]# ceph config set global log_to_stderr false
[ceph: root@host01 /]# 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. When logging to files, Ceph logs are located in /var/log/ceph/CLUSTER_FSID.

To enable logging to files, set the following values:

[ceph: root@host01 /]# ceph config set global log_to_file true
[ceph: root@host01 /]# ceph config set global mon_cluster_log_to_file true

Important: Log rotation to a non-default path is not currently supported.

Note: Disable logging to stderr to avoid double logs.

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.