OCP code to set up swap. Be very careful when editing this!

setupswap.yaml

kind: MachineConfig
apiVersion: machineconfiguration.openshift.io/v1
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: 91-worker-swap
spec:
  config:
    ignition:
      version: 3.4.0
    systemd:
      units:
        - contents: |
            [Unit]
            Description=Provision and enable swap
            ConditionFirstBoot=no
            [Service]
            Type=oneshot
            ExecStart=/bin/sh -c 'declare -A used_disks; rootdisk=$(df /boot | tail -1 | sed "s/ .*//") && \
            if [[ -n "${rootdisk:-}" ]] ; then used_disks["$(readlink -f "$rootdisk" | sed "s/[0-9]*\$//")"]=1; fi && \
            if [[ -d /mnt/local-storage/localfile ]] ; then \
            while read -r disk ; do \
            if [[ -n "$disk" ]] ; then used_disks["$disk"]=1; fi ; \
            done <<< "$(cd /mnt/local-storage/localfile/ && readlink -f * | sed "s/[0-9]*\$//")" ; fi && \
            for d in /dev/sd? ; do \
            if [[ -z "${used_disks[$d]:-}" && -b "$d" ]] ; then \
            echo "Using disk $d for swap" && \
            disk="$d" && \
            sudo mkswap "$disk" && \
            sudo swapon "$disk" && \
            sudo systemctl set-property --runtime system.slice MemorySwapMax=0 IODeviceLatencyTargetSec="/ 50ms" && \
            free -h ; \
            break ; \
            fi; \
            done'
            [Install]
            RequiredBy=kubelet-dependencies.target
          enabled: true
          name: swap-provision.service

• Before applying this, you MUST ensure that you've applied a KubeletConfig that sets failSwapOn: false and waited for it to be applied to every node. Otherwise the kubelet will fail to start and cleaning it up is messy.

• Be very careful when editing this file. If you make a change resulting in this service failing, the kubelet will not start, you'll have to roll back the machineconfig, and then manually reboot the nodes this was applied to.