daemonset.yaml

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: root-ssh-manager
  namespace: kube-system
spec:
  selector:
    matchLabels:
     app: root-ssh-manager
  template:
    metadata:
      labels:
        app: root-ssh-manager
    spec:
      containers:
        - name: update-ssh-authorized-keys
          image: busybox:latest
          securityContext:
            privileged: true
          command:
            - "/bin/sh"
            - "-c"
            - |
              set -o errexit
              set -o xtrace
              umask 0077
              while true
              do
                mkdir -p /mnt/root/.ssh
                rm -f /mnt/root/.ssh/authorized_keys_new
                for key in $(find /mnt/keys -type f); do (cat ${key}; echo) >> /mnt/root/.ssh/authorized_keys_new; done
                mv /mnt/root/.ssh/authorized_keys_new /mnt/root/.ssh/authorized_keys
                sleep 60s;
              done
          volumeMounts:
            - name: root
              mountPath: /mnt/root
            - name: ssh-keys
              mountPath: /mnt/keys
      volumes:
        - name: root
          hostPath:
            path: /root
        - name: ssh-keys
          configMap:
            name: root-ssh-pubkeys