We can inject a sidecar proxy in a running deployment of pods. Envoy is the default proxy for Istio.

We could use the "istioctl kube-inject" command to inject a sidecar proxy into a deployment, for example the below nginx deployment:

We create our deployment using the below command:

Then, we check our nginx pods using the below command: 

Then, we use the below command to create an envoy side container in each pod:

We recheck our pods to see if the sidecar containers have been successfully added to our deployment as follows:

We see that we have two containers in each pod.

Remark:

Using the above method, the original Yaml file of our deployment remains unchanged.