DaemonSet Update
DaemonSet Update
Create a Daemonet
First of all, we need to create a daemonset. Create the following file:
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: ds-one
spec:
selector:
matchLabels:
system: ds-one
template:
metadata:
labels:
system: ds-one
spec:
containers:
- name: nginx
image: r.deso.tech/library/nginx
ports:
- containerPort: 80
Apply the file:
kubectl apply -f ds.yaml
daemonset/ds-one created
Update a DaemonSet (OnDelete)
Kubernetes supports two strategies for upgrading daemonsets, let’s find the default:
kubectl get ds ds-one -o yaml \
| grep -A 3 Strategy
Edit the object to use the OnDelete update strategy. This would allow the manual termination of some of the pods,
resulting in an updated image when they are recreated.
kubectl edit ds ds-one
.... updateStrategy: rollingUpdate: maxUnavailable: 1 type: OnDelete # <-- 'RollingUpdate' should be replaced with 'OnDelete' ....
Update the DaemonSet to use a newer version of the nginx server.
This time use the set command instead of edit.
Set the version to be 1.16.1-alpine.
kubectl set image ds ds-one nginx=httpd
daemonset.apps/ds-one image updated
Verify that the Image: parameter for the Pod checked in the previous section is unchanged.
kubectl describe po ds-one-b2dcv | grep Image:
Image: r.deso.tech/library/nginx
Delete a Pod. Wait until the replacement Pod is running and check the version.
kubectl delete po ds-one-b2dcv
pod "ds-one-b2dcv" deleted
kubectl get pod
NAME READY STATUS RESTARTS AGE ds-one-xc86w 1/1 Running 0 21s ds-one-z31r4 1/1 Running 0 4m12s
kubectl describe pod ds-one-xc86w | grep Image:
Image: r.deso.tech/library/httpd
View the image running on the older pods. It should still show nginx.
kubectl describe pod ds-one-z31r4 | grep Image:
Image: r.deso.tech/library/nginx
View the history of changes for the DaemonSet. You should see two revisions listed.
As we did not use the --record option we didn’t see why the object updated.
kubectl rollout history ds ds-one
REVISION CHANGE-CAUSE 1 <none> 2 <none>
View the settings for the various versions of the DaemonSet.
The Image: line should be the only difference between the two outputs.
kubectl rollout history ds ds-one --revision=1
Pod Template: Labels: system=DaemonSetOne Containers: nginx: Image: r.deso.tech/library/nginx Port: 80/TCP Environment: <none> Mounts: <none> Volumes: <none>
kubectl rollout history ds ds-one --revision=2
.... Image: r.deso.tech/library/httpd .....
Use kubectl rollout undo to change the DaemonSet back to an earlier version.
As we are still using the OnDelete strategy there should be no change to the Pods.
kubectl rollout undo ds ds-one --to-revision=1
daemonset.apps/ds-one rolled back
kubectl describe pod ds-one-xc86w | grep Image:
Image: r.deso.tech/library/nginx
Delete the Pod, wait for the replacement to spawn then check the image version again.
kubectl delete pod ds-one-xc86w
pod "ds-one-xc86w" deleted
kubectl get pod
NAME READY STATUS RESTARTS AGE ds-one-qc72k 1/1 Running 0 10s ds-one-xc86w 0/1 Terminating 0 12m ds-one-z31r4 1/1 Running 0 28m
kubectl describe po ds-one-qc72k | grep Image:
Image: r.deso.tech/library/nginx
View the details of the DaemonSet. The Image should be v1.15.1 in the output.
kubectl describe ds | grep Image:
Image: r.deso.tech/library/nginx
View the current configuration for the DaemonSet in YAML output.
Look for the updateStrategy:
kubectl get ds ds-one -o yaml
apiVersion: apps/v1 kind: DaemonSet ..... terminationGracePeriodSeconds: 30 updateStrategy: type: OnDelete status: currentNumberScheduled: 2 .....
Update a DaemonSet (RollingUpdate)
Create a new DaemonSet, this time setting the update policy to RollingUpdate.
Begin by generating a new config file.
kubectl get ds ds-one -o yaml > ds2.yaml
Edit the file. Change the name, around line 70 and the update strategy around line 101, back to the default
RollingUpdate.
vim ds2.yaml
.... name: ds-two .... type: RollingUpdate
Create the new DaemonSet and verify the nginx version in the new pods.
kubectl create -f ds2.yaml
daemonset.apps/ds-two created
kubectl get pod
NAME READY STATUS RESTARTS AGE ds-one-qc72k 1/1 Running 0 28m ds-one-z31r4 1/1 Running 0 57m ds-two-10khc 1/1 Running 0 5m ds-two-kzp9g 1/1 Running 0 5m
kubectl describe po ds-two-10khc | grep Image:
Image: r.deso.tech/library/nginx
Edit the configuration file and set the image to a newer version such as 1.16.1-alpine. Include the --record option.
kubectl edit ds ds-two --record
.... - image: r.deso.tech/library/httpd .....
View the age of the DaemonSets. It should be around ten minutes old, depending on how fast you type.
kubectl get ds ds-two
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE-SELECTOR AGE ds-two 2 2 2 2 2 <none> 10m
Now view the age of the Pods. Two should be much younger than the DaemonSet. They are also a few seconds apart
due to the nature of the rolling update where one then the other pod was terminated and recreated.
kubectl get pod
NAME READY STATUS RESTARTS AGE ds-one-qc72k 1/1 Running 0 36m ds-one-z31r4 1/1 Running 0 1h ds-two-2p8vz 1/1 Running 0 34s ds-two-8lx7k 1/1 Running 0 32s
Verify the Pods are using the new version of the software.
kubectl describe po ds-two-8lx7k | grep Image:
Image: r.deso.tech/library/httpd
View the rollout status and the history of the DaemonSets.
kubectl rollout status ds ds-two
daemon set "ds-two" successfully rolled out
kubectl rollout history ds ds-two
REVISION CHANGE-CAUSE 1 <none> 2 kubectl edit ds ds-two --record=true
View the changes in the update they should look the same as the previous history, but did not require the Pods to be deleted for the update to take place.
kubectl rollout history ds ds-two --revision=2
... Image: r.deso.tech/library/httpd
Clean up the environment by removing the DaemonSets.
kubectl delete ds ds-one ds-two
daemonset.apps "ds-one" deleted daemonset.apps "ds-two" deleted