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Make sure your imagePullPolicy is set to Always(this is the default).
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That means when a pod is deleted, a new pod will ensure it has the current version of the image.
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Then refresh all your pods.
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The simplest way to refresh all your pods is to just delete them and they will be recreated with the latest image.
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This immediately destroys all your pods which will cause a service outage.
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Do this with kubectl delete pod -l <name>=<value> where name and value are the label selectors your deployment uses.
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A better way is to edit your deployment and modify the deployment pod spec to add or change any annotation.
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This will cause all your pods to be deleted and rescheduled, but this method will also obey your rollingUpdate strategy, meaning no downtime assuming your rollingUpdate strategy already behaves properly.
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Setting a timestamp or a version number is convenient, but any change to pod annotations will cause a rolling update.
For a deployment named nginx, this can be done with:
PATCH='{"spec":{"template":{"metadata":{"annotations":{"timestamp":"'$(date)'"}}}}}'
kubectl patch deployment nginx -p "$PATCH"
It is considered bad practice to rely on the :latest docker image tag in your deployments, because using :latest there is no way to rollback or specify what version of your image to use.
It is better to update the deployment with an exact version of the image and use --record so that you can use:
kubectl rollout undo deployment <deployment> or other commands to manage rollouts.
