This error occurs when you click on the Ceph tab in the Proxmox GUI without initializing the Ceph storage. If Ceph is not going to be used along with Proxmox on the same cluster, then this error should simply be ignored. But if any Proxmox node is going to be used to manage Ceph through the Proxmox GUI, then simply copy the Ceph configuration file from /etc/pve/ceph.conf into /etc/ceph/ceph.conf, which will allow you to manage Ceph even if there is no OSD or mon in that node. Since Ceph configuration may change over time, it is recommended to create a symlink for the configuration file instead of a simple copy. The following command will create a symlink of the Ceph configuration file in the /etc/ceph directory:

      # ln -s /etc/pve/ceph.conf /etc/ceph/ceph.conf