onechart/website/docs/examples/custom-command.md

OneChart settings for overriding the default command to run:

image:
  repository: debian
  tag: stable-slim

command: |
  while true; date; sleep 2; done

Check the Kubernetes manifest:

cat << EOF > values.yaml
image:
  repository: debian
  tag: stable-slim

command: |
  echo "hello"
EOF

helm template my-release onechart/onechart -f values.yaml