Deploy 3 nodes Ceph cluster for testing.

ceph3nodes.sh

#!/bin/bash
set -e

CEPH_VER=${CEPH_VER:-"15.2.1"}
OSD_DEV=${OSD_DEV:-/dev/sdb}

ssh_test() {
    if [[ $(ssh root@$1 exit) -ne 0 ]]
    then
        echo "failed to login $1 as root" && exit 1
    fi
}

append_hosts() {
    sed -i -e /$2/d /etc/hosts

    echo "$1    $2" >> /etc/hosts
}

docker() {
    yum install -y yum-utils
    yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
    yum install docker-ce docker-ce-cli containerd.io -y
    systemctl start docker && systemctl enable docker
}

deps() {
    ceph_ver=$1
    yum install -y wget python3 epel-release
    rm -f /etc/yum.repos.d/ceph.repo
    cat <<EOF > /etc/yum.repos.d/ceph.repo
[Ceph]
name=Ceph basearch
baseurl=https://download.ceph.com/rpm-$ceph_ver/el7/basearch
enabled=1
gpgcheck=1
gpgkey=https://download.ceph.com/keys/release.gpg

[Ceph-noarch]
name=Ceph noarch
baseurl=https://download.ceph.com/rpm-$ceph_ver/el7/noarch
enabled=1
gpgcheck=1
gpgkey=https://download.ceph.com/keys/release.gpg

[Ceph-source]
name=Ceph SRPMS
baseurl=https://download.ceph.com/rpm-$ceph_ver/el7/SRPMS
enabled=1
gpgcheck=1
gpgkey=https://download.ceph.com/keys/release.gpg
EOF
    sed -i -e 's/basearch/\$basearch/g' /etc/yum.repos.d/ceph.repo
    rpm --import 'https://download.ceph.com/keys/release.asc'
    yum makecache
    yum install ceph-common -y
    rm -rf /usr/local/bin/cephadm
    wget -P /usr/local/bin https://raw.githubusercontent.com/ceph/ceph/v$ceph_ver/src/cephadm/cephadm && chmod +x /usr/local/bin/cephadm
}

chrony() {
    cat <<EOF > /etc/chrony.conf
server $1 iburst

# Ignor source level
stratumweight 0

# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift

# Allow the system clock to be stepped in the first three updates
# if its offset is larger than 1 second.
makestep 1.0 3

# Enable kernel synchronization of the real-time clock (RTC).
rtcsync

# Enable hardware timestamping on all interfaces that support it.
#hwtimestamp *

# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2

# Allow NTP client access from local network.
allow 0.0.0.0/0

bindcmdaddress 127.0.0.1
bindcmdaddress ::1

# Serve time even if not synchronized to a time source.
EOF

    if [[ $1 == "localhost" ]]
    then
        echo "local stratum 10" >> /etc/chrony.conf
    fi

    cat <<EOF >> /etc/chrony.conf

# Specify file containing keys for NTP authentication.
keyfile /etc/chrony.keys

# Specify directory for log files.
logdir /var/log/chrony

# Select which information is logged.
#log measurements statistics tracking

noclientlog
EOF
    systemctl restart chronyd && systemctl enable chronyd
}

main() {
    # check
    if [[ -z $1 ]]
    then
        echo "missing IP/hostname of node2" && exit 1
    fi

    if [[ -z $2 ]]
    then
        echo "missing IP/hostname of node3" && exit
    fi

    # IP address of host
    ip_addr=$(hostname -I | cut -d ' ' -f 1)

    # test ssh connection
    for host in localhost $1 $2
    do
        ssh_test $host
    done

    # stop and disable firewalld
    for host in localhost $1 $2
    do
        ssh root@$host "systemctl stop firewalld && systemctl disable firewalld"
    done

    # set up chrony docker and install dependencies
    chrony localhost
    docker
    deps $CEPH_VER
    for host in $1 $2
    do
        ssh root@$host << EOF
        $(typeset -f chrony)
        chrony $ip_addr
        $(typeset -f docker)
        docker
        $(typeset -f deps)
        deps $CEPH_VER
EOF
    done

    host1=$(hostname)
    host2=$(ssh root@$1 "hostname")
    host3=$(ssh root@$2 "hostname")
    for host in $ip_addr $1 $2
    do
        ssh root@$host << EOF
        $(typeset -f append_hosts)
        append_hosts $ip_addr $host1
        append_hosts $1 $host2
        append_hosts $2 $host3
EOF
    done

    # bootstrap
    export CEPHADM_IMAGE=docker.io/ceph/ceph:v$CEPH_VER
    cephadm bootstrap --mon-ip $ip_addr

    # wait for 5 mins
    echo "wait for 5 mins"
    sleep 5m

    for host in $host2 $host3
    do
        ssh-copy-id -f -i /etc/ceph/ceph.pub root@$host
        ceph orch host add $host
    done

    # wait for 5 mins
    echo "wait for 5 mins again"
    sleep 5m

    for host in $host1 $host2 $host3
    do
        ceph orch daemon add osd $host:$OSD_DEV
    done

    # wait for 5 mins
    sleep 5m
    echo "mission complete!"
}

main "$@"

Only for CentOS!
Make sure node1 ssh to node2 and node3 with key pair.

Run this on first node(e.g. 10.211.55.123):

$ curl -OsL https://gist.githubusercontent.com/crazytaxii/f3292e86846b6cafdba3778392241403/raw/111cd1fa522b9b5363fe854cd83e20eec70123f6/ceph3nodes.sh && chmod +x ./ceph3nodes.sh
$ ./ceph3nodes.sh 10.211.55.124 10.211.55.125