Installation (ceph-daemon)

A new Ceph cluster is deployed by bootstrapping a cluster on a single node, and then adding additional nodes and daemons via the CLI or GUI dashboard.

Get ceph-daemon

The ceph-daemon utility is used to bootstrap a new Ceph Cluster. You can get the utility by either installing a package provided by your Linux distribution:

sudo apt install -y ceph-daemon   # or,
sudo dnf install -y ceph-daemon   # or,
sudo yum install -y ceph-daemon

or by simply downloading the standalone script manually:

curl --silent --remote-name --location
chmod +x ceph-daemon
sudo install -m 0755 ceph-daemon /usr/sbin    # optional!

Bootstrap a new cluster

To create a new cluster, you need to know:

  • Which IP address to use for the cluster’s first monitor. This is normally just the IP for the first cluster node. If there are multiple networks and interfaces, be sure to choose one that will be accessible by any hosts accessing the Ceph cluster.

To bootstrap the cluster,:

sudo ceph-daemon bootstrap --mon-ip *<mon-ip>*

This command does a few things:

  • Creates a monitor and manager daemon for the new cluster on the local host. A minimal configuration file needed to communicate with the new cluster is written to ceph.conf in the local directory.

  • A copy of the client.admin administrative (privileged!) secret key is written to ceph.client.admin.keyring in the local directory.

  • Generates a new SSH key, and adds the public key to the local root user’s /root/.ssh/authorized_keys file. A copy of the public key is written to in the local directory.

Interacting with the cluster

You can easily start up a container that has all of the Ceph packages installed to interact with your cluster:

sudo ceph-daemon shell --config ceph.conf --keyring ceph.keyring

The --config and --keyring arguments will bind those local files to the default locations in /etc/ceph inside the container to allow the ceph CLI utility to work without additional arguments. Inside the container, you can check the cluster status with:

ceph status

In order to interact with the Ceph cluster outside of a container, you need to install the Ceph client packages and install the configuration and privileged administrator key in a global location:

sudo apt install -y ceph-common   # or,
sudo dnf install -y ceph-common   # or,
sudo yum install -y ceph-common

sudo install -m 0644 ceph.conf /etc/ceph/ceph.conf
sudo install -m 0600 ceph.keyring /etc/ceph/ceph.keyring

Adding hosts to the cluster

For each new host you’d like to add to the cluster, you need to do two things:

  1. Install the cluster’s public SSH key in the new host’s root user’s authorized_keys file. For example,:

    cat | ssh root@*newhost* tee -a /root/.ssh/authorized_keys
  2. Tell Ceph that the new node is part of the cluster:

    ceph orchestrator host add *newhost*

Deploying additional monitors

Normally a Ceph cluster has at least three (or, preferably, five) monitor daemons spread across different hosts. Since we are deploying a monitor, we again need to specify what IP address it will use, either as a simple IP address or as a CIDR network name.

To deploy additional monitors,:

ceph orchestrator mon update *<new-num-monitors>* *<host1:network1> [<host1:network2>...]*

For example, to deploy a second monitor on newhost using an IP address in network,:

ceph orchestrator mon update 2 newhost:

Deploying OSDs

To add an OSD to the cluster, you need to know the device name for the block device (hard disk or SSD) that will be used. Then,:

ceph orchestrator osd create *<host>*:*<path-to-device>*

For example, to deploy an OSD on host newhost’s SSD,:

ceph orchestrator osd create newhost:/dev/disk/by-id/ata-WDC_WDS200T2B0A-00SM50_182294800028

Deploying manager daemons

It is a good idea to have at least one backup manager daemon. To deploy one or more new manager daemons,:

ceph orchestrator mgr update *<new-num-mgrs>* [*<host1>* ...]

Deploying MDSs

In order to use the CephFS file system, one or more MDS daemons is needed.