如何判断我的容器是否在 Kube.netes 集群中运行？

Question

How can I tell whether or not I am running inside a kube.netes cluster? With docker I can check if /.dockerinit exist. Is there an equivalent?

Answer 1

You can check for KUBERNETES_SERVICE_HOST environment variable.

This variable is always exported in an environment where the container is executed.

Refer to https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/#environment-variables

Answer 2

You can pass environment variables to your containers in the pod spec. You can even expose some pod information to the containers via environment variables using the downward API .

Answer 3

With the default configuration, Kubernetes will mount the serviceaccount secrets into pods. Simply check for the existence of this folder: /var/run/secrets/kubernetes.io . No need to set environment variables. In ruby I would do the following:

if File.exists?('/.dockerenv')
  puts "I'm running in a docker container"
end

if File.exists?('/var/run/secrets/kubernetes.io')
  puts "I'm also running in a Kubernetes pod"
end

Answer 4

One option is to check the /etc/hosts file - there is by default the comment that the file is maintained by K8s.

Anyway the best way is to def your own env variable in deployment, so use some template tools like helm to gen deployment and define some general template.