OCP 4 create a new machineset in AWS based on existing.

awsmkmachineset.sh

#!/usr/bin/env bash

set -euo pipefail
IFS=$'\n\t'

AWS_INSTANCE_TYPE="p2.xlarge"
REPLICAS=1
DRY_RUN=0

USAGE="$(basename "${BASH_SOURCE[0]}") [options]

Options:
  -h | --help            show this message and exit
  -r | --replicas N      number of desired instances of the new machineset
  -t | --type TYPE       AWS EC2 instance type for the new machines
  -m | --machineset MN   an existing machineset to use as a base; if not given, whil be randomly
                         selected
  --role NAME            part of machineconfig's name; the resulting name will be:
                            <cluster-id>-<NAME>-<aws-zone>
                         if not given, will be set to <TYPE>-worker
  --dry-run              just print the resulting machine set and exit
"

function determineMachineSet() {
     oc get machineset -n openshift-machine-api | \
         awk 'match($0, /^([^-]+-[^-]+-worker-[^ ]+)/, a) {print a[1]}' | \
         sort -R | head -n 1
}

function mkMachineSetSpec() {
    local roleName="$1"
    local msSpec="$(oc get machineset -n openshift-machine-api -o json "$MACHINESET")"

    local newMSName="$(jq -r '.metadata.name' <<<"$msSpec" | sed 's/^\([^-]\+-[^-]\+\)-[^-]\+-\(.*\)/\1-'"$NAME"'-\2/')"
    if [[ -z "${newMSName:-}" ]]; then
        printf 'Failed to determine new machines set name!\n' >&2
        return 1
    fi

    oc get machineset -n openshift-machine-api -o json "$MACHINESET" | jq 'del(
        .status,
        .metadata.creationTimestamp,
        .metadata.uid,
        .metadata.selfLink,
        .metadata.resourceVersion,
        .metadata.generation,
        .spec.template.spec.metadata,
        .spec.template.metadata.creationTimeStamp,
        .spec.template.spec.providerSpec.value.metadata
    ) | .metadata.name |= "'"$newMSName"'" |
        .spec.replicas |= '"$REPLICAS"' |
        .spec.selector.matchLabels["machine.openshift.io/cluster-api-machineset"] |= "'"$newMSName"'" |
        .spec.template.metadata.labels["machine.openshift.io/cluster-api-machineset"] |= "'"$newMSName"'" |
        .spec.template.metadata.labels["machine.openshift.io/cluster-api-machine-role"] |= "'"$NAME"'" |
        .spec.template.metadata.labels["machine.openshift.io/cluster-api-machine-type"] |= "'"$NAME"'" |
        .spec.template.spec.metadata.labels["node-role.kubernetes.io/'"$NAME"'"] |= "" |
        .spec.template.spec.providerSpec.value.instanceType |= "'"$AWS_INSTANCE_TYPE"'"'
}

function join() { local IFS="$1"; shift; echo "$*"; }

long_options=( replicas: type: machineset: help name: dry-run )
TMPARGS="$(getopt -l "$(join , "${long_options[@]}")" -o r:t:m:n:h \
    -n "$(basename "${BASH_SOURCE[0]}")" -- "$@")"
eval set -- "$TMPARGS"

while true; do
    case "$1" in
        --role)
            NAME="$2"
            shift 2
            ;;
        -h | --help)
            printf "$USAGE"
            exit 0
            ;;
        -t | --type)
            AWS_INSTANCE_TYPE="$2"
            shift 2;
            ;;
        -r | --replicas)
            REPLICAS="$2"
            shift 2
            ;;
        -m | --machineset)
            MACHINESET="$2"
            shift 2
            ;;
        --dry-run)
            DRY_RUN=1
            shift 1
            ;;
        --)
            shift 1
            break
            ;;
        *)
            printf 'Invalid option "%s"\n!' "$1" >&2
            exit 1
            ;;
    esac
done

if [[ -z "${MACHINESET:-}" ]]; then
    MACHINESET="$(determineMachineSet)"
fi
if [[ -z "${MACHINESET:-}" ]]; then
    printf 'Failed to determine machine set!\n' >&2
    exit 1;
fi

if [[ -z "${NAME:-}" ]]; then
    NAME="$(tr '.' '-' <<<"${AWS_INSTANCE_TYPE}")-worker"
fi

if ! which jq >/dev/null 2>&1; then
    if [[ "$DRY_RUN" == 1 ]]; then
        printf 'Please install jq first.\n' >&2
        exit 1
    elif ! sudo yum install -y jq; then
        printf 'Failed to install jq! Please install it before trying again.\n' >&2
        exit 1
    fi
fi

newMSSpec="$(mkMachineSetSpec "$NAME")"
if [[ "$DRY_RUN" == 1 ]]; then
    cat <<<"$newMSSpec"
    exit 0
fi

oc create -n openshift-machine-api -f - <<<"${newMSSpec}"