This document is for a development version of Ceph.
Deploying a new Ceph cluster¶
Cephadm creates a new Ceph cluster by “bootstrapping” on a single host, expanding the cluster to encompass any additional hosts, and then deploying the needed services.
Podman or Docker for running containers
Time synchronization (such as chrony or NTP)
LVM2 for provisioning storage devices
Any modern Linux distribution should be sufficient. Dependencies are installed automatically by the bootstrap process below.
See the section Compatibility With Podman Versions for a table of Ceph versions that are compatible with Podman. Not every version of Podman is compatible with Ceph.
cephadm command can
bootstrap a new cluster
launch a containerized shell with a working Ceph CLI
aid in debugging containerized Ceph daemons
There are two ways to install
curlto fetch the most recent version of the standalone script.
curl --silent --remote-name --location https://github.com/ceph/ceph/raw/pacific/src/cephadm/cephadm
chmod +x cephadm
This script can be run directly from the current directory:
Although the standalone script is sufficient to get a cluster started, it is convenient to have the
cephadmcommand installed on the host. To install the packages that provide the
cephadmcommand, run the following commands:
./cephadm add-repo --release pacific ./cephadm install
cephadmis now in your PATH by running
which cephadmcommand will return this:
The methods of installing
cephadm in this section are distinct from the curl-based method above. Use either the curl-based method above or one of the methods in this section, but not both the curl-based method and one of these.
Some Linux distributions may already include up-to-date Ceph packages. In that case, you can install cephadm directly. For example:
In Ubuntu:apt install -y cephadm
In Fedora:dnf -y install cephadm
In SUSE:zypper install -y cephadm
Bootstrap a new cluster¶
What to know before you bootstrap¶
The first step in creating a new Ceph cluster is running the
bootstrap command on the Ceph cluster’s first host. The act of running the
cephadm bootstrap command on the Ceph cluster’s first host creates the Ceph
cluster’s first “monitor daemon”, and that monitor daemon needs an IP address.
You must pass the IP address of the Ceph cluster’s first host to the
bootstrap command, so you’ll need to know the IP address of that host.
If there are multiple networks and interfaces, be sure to choose one that will be accessible by any host accessing the Ceph cluster.
Running the bootstrap command¶
ceph bootstrap command:
cephadm bootstrap --mon-ip *<mon-ip>*
This command will:
Create a monitor and manager daemon for the new cluster on the local host.
Generate a new SSH key for the Ceph cluster and add it to the root user’s
Write a copy of the public key to
Write a minimal configuration file to
/etc/ceph/ceph.conf. This file is needed to communicate with the new cluster.
Write a copy of the
client.adminadministrative (privileged!) secret key to
_adminlabel to the bootstrap host. By default, any host with this label will (also) get a copy of
Further information about cephadm bootstrap¶
The default bootstrap behavior will work for most users. But if you’d like
immediately to know more about
cephadm bootstrap, read the list below.
Also, you can run
cephadm bootstrap -h to see all of
By default, Ceph daemons send their log output to stdout/stderr, which is picked up by the container runtime (docker or podman) and (on most systems) sent to journald. If you want Ceph to write traditional log files to
--log-to-fileoption during bootstrap.
Larger Ceph clusters perform better when (external to the Ceph cluster) public network traffic is separated from (internal to the Ceph cluster) cluster traffic. The internal cluster traffic handles replication, recovery, and heartbeats between OSD daemons. You can define the cluster network by supplying the
--cluster-networkoption to the
bootstrapsubcommand. This parameter must define a subnet in CIDR notation (for example
cephadm bootstrapwrites to
/etc/cephthe files needed to access the new cluster. This central location makes it possible for Ceph packages installed on the host (e.g., packages that give access to the cephadm command line interface) to find these files.
Daemon containers deployed with cephadm, however, do not need
/etc/cephat all. Use the
--output-dir *<directory>*option to put them in a different directory (for example,
.). This may help avoid conflicts with an existing Ceph configuration (cephadm or otherwise) on the same host.
You can pass any initial Ceph configuration options to the new cluster by putting them in a standard ini-style configuration file and using the
--config *<config-file>*option. For example:
$ cat <<EOF > initial-ceph.conf [global] osd crush chooseleaf type = 0 EOF $ ./cephadm bootstrap --config initial-ceph.conf ...
--ssh-user *<user>*option makes it possible to choose which ssh user cephadm will use to connect to hosts. The associated ssh key will be added to
/home/*<user>*/.ssh/authorized_keys. The user that you designate with this option must have passwordless sudo access.
If you are using a container on an authenticated registry that requires login, you may add the three arguments:
--registry-url <url of registry>
--registry-username <username of account on registry>
--registry-password <password of account on registry>
--registry-json <json file with login info>
Cephadm will attempt to log in to this registry so it can pull your container and then store the login info in its config database. Other hosts added to the cluster will then also be able to make use of the authenticated registry.
Enable Ceph CLI¶
Cephadm does not require any Ceph packages to be installed on the
host. However, we recommend enabling easy access to the
command. There are several ways to do this:
cephadm shellcommand launches a bash shell in a container with all of the Ceph packages installed. By default, if configuration and keyring files are found in
/etc/cephon the host, they are passed into the container environment so that the shell is fully functional. Note that when executed on a MON host,
cephadm shellwill infer the
configfrom the MON container instead of using the default configuration. If
--mount <path>is given, then the host
<path>(file or directory) will appear under
/mntinside the container:
cephcommands, you can also run commands like this:
cephadm shell -- ceph -s
You can install the
ceph-commonpackage, which contains all of the ceph commands, including
mount.ceph(for mounting CephFS file systems), etc.:
cephadm add-repo --release pacific cephadm install ceph-common
Confirm that the
ceph command is accessible with:
Confirm that the
ceph command can connect to the cluster and also
its status with:
Next, add all hosts to the cluster by following Adding Hosts.
By default, a
ceph.conf file and a copy of the
are maintained in
/etc/ceph on all hosts with the
_admin label, which is initially
applied only to the bootstrap host. We usually recommend that one or more other hosts be
_admin label so that the Ceph CLI (e.g., via
cephadm shell) is easily
accessible on multiple hosts. To add the
_admin label to additional host(s),
ceph orch host label add *<host>* _admin
Adding additional MONs¶
A typical Ceph cluster has three or five monitor daemons spread across different hosts. We recommend deploying five monitors if there are five or more nodes in your cluster.
Please follow Deploying additional monitors to deploy additional MONs.
To add storage to the cluster, either tell Ceph to consume any available and unused device:
ceph orch apply osd --all-available-devices
Or See Deploy OSDs for more detailed instructions.