ocp-hosts-daemonset.yaml

# ----------------------------------------------------------------------------
# Title: Updating Hostfile entries on Openshift worker nodes.
# Author: Chris Greenwood (chris.greenwood@uk.ibm.com)
# based on a similar script by Ravi Konuru (rkonuru@us.ibm.com)
# Last Updated: 04/06/2020

# How to use:
# 1. Update the HOSTDNS_1 and HOSTIP_1 variables with the DNS name and IP 
#    address that you want it to resolve to.
# 2. If you need further hosts file entries, export additional variables at the
#    top of the script and then  
#    Be CAREFUL OF SPACING and all lines WITHIN SHELL SCRIPT SECTION should
#    END WITH SEMI-COLON (;)! YOU SHOULD NOT NEED TO MAKE ANY OTHER CHANGES.
# 2. Run "oc apply -f ocp-hosts-daemonset.yaml"
# 3. Run "oc get pods". You should see new "updatehosts-xxxxx" pods which
#    will reach a "Running" state within a few seconds.
# 4. To view the logs and status of this script, run "kubectl logs <podname>".
#    (The same log messages will appear within IBM LogDNA for Log Analysis if
#    it has been configured with your ROKS Cluster.)
# ----------------------------------------------------------------------------

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: updatehosts
spec:
  selector:
    matchLabels:
      name: updatehosts
  template:
    metadata:
      labels:
        name: updatehosts
    spec:
      hostNetwork: true
      hostPID: true
      hostIPC: true
      containers:
        - resources:
            requests:
              cpu: 0.1
          securityContext:
            privileged: true
          image: alpine
          name: updatehosts
          command: ["/bin/sh", "-c"]
          args:
            - >
              export HOSTDNS_1=<host dns>;
              export HOSTIP_1=<host ip>;

              HOSTNAME=`hostname`;
              echo "";
              echo "Running updatehosts on worker node $HOSTNAME";
              echo "=== current contents of /etc/hosts ====";
              cat /host/etc/hosts;
              echo "";
              echo "Making a backup copy /etc/hosts before appending entries $HOSTDNS_1 and $HOSTIP_1.";
              echo "-------------------------------------------------------";
              cp /host/etc/hosts /host/etc/hosts.orig;

              echo "  " >> /host/etc/hosts;
              echo "# added by updatehosts daemonset. " >> /host/etc/hosts;
              echo $HOSTIP_1  $HOSTDNS_1 >> /host/etc/hosts;
              echo "";
              echo "====Updated /etc/hosts file =======";
              echo "";
              cat /host/etc/hosts;
              echo "Finished. Pod going to sleep.";
              echo "";
              while true; do
                sleep 100000;
              done;

          volumeMounts:
            - name: host-volume
              mountPath: /host
      volumes:
        - name: host-volume
          hostPath:
            path: /