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Example Kubernetes pod for the multi-container sidecar design pattern
# Example YAML configuration for the sidecar pattern.
# It defines a main application container which writes
# the current date to a log file every five seconds.
# The sidecar container is nginx serving that log file.
# (In practice, your sidecar is likely to be a log collection
# container that uploads to external storage.)
# To run:
# kubectl apply -f pod.yaml
# Once the pod is running:
# (Connect to the sidecar pod)
# kubectl exec pod-with-sidecar -c sidecar-container -it bash
# (Install curl on the sidecar)
# apt-get update && apt-get install curl
# (Access the log file via the sidecar)
# curl 'http://localhost:80/app.txt'
apiVersion: v1
kind: Pod
name: pod-with-sidecar
# Create a volume called 'shared-logs' that the
# app and sidecar share.
- name: shared-logs
emptyDir: {}
# In the sidecar pattern, there is a main application
# container and a sidecar container.
# Main application container
- name: app-container
# Simple application: write the current date
# to the log file every five seconds
image: alpine # alpine is a simple Linux OS image
command: ["/bin/sh"]
args: ["-c", "while true; do date >> /var/log/app.txt; sleep 5;done"]
# Mount the pod's shared log file into the app
# container. The app writes logs here.
- name: shared-logs
mountPath: /var/log
# Sidecar container
- name: sidecar-container
# Simple sidecar: display log files using nginx.
# In reality, this sidecar would be a custom image
# that uploads logs to a third-party or storage service.
image: nginx:1.7.9
- containerPort: 80
# Mount the pod's shared log file into the sidecar
# container. In this case, nginx will serve the files
# in this directory.
- name: shared-logs
mountPath: /usr/share/nginx/html # nginx-specific mount path
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RealKanashii commented Jan 12, 2022

to send any command to a container inside a pod that is not default (there's more than 1) use -c "containerName". Example:
kubectl exec -it pod-with-sidecar -c sidecar-container -- ls -la /usr/share/nginx/html

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