How to know a Pod s own IP address from inside a container in the Pod

Question

Kubernetes assigns an IP address for each container  but how can I acquire the IP address from a container in the Pod  I couldn t find the way from documentations   Edit  I m going to run Aerospike cluster in Kubernetes  and the config files need its own IP address  And I m attempting to use confd to set the hostname  I would use the environment variable if it was set

User · Answer

The container s IP address should be properly configured inside of its network namespace  so any of the standard linux tools can get it  For example  try ifconfig  ip addr show  hostname -I  etc  from an attached shell within one of your containers to test it out

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kubectl describe pods  lt name of pod gt  will give you some information including the IP

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In some cases  instead of relying on downward API  programmatically reading the local IP address  from network interfaces  from inside of the container also works   For example  in golang  https   stackoverflow com a 31551220 6247478

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You could use  kubectl describe pod  hostname    grep IP   sed -E  s IP    space          which is based on what  mibbit suggested   This takes the following facts into account    hostname is set to POD s name but this might change in the future kubectl was manually placed in the container  possibly when the image was built  Kubernetes provides a service account credential to the container implicitly as described in Accessing the Cluster   Accessing the API from a Pod  i e   var run secrets kubernetes io serviceaccount in the container

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The simplest answer is to ensure that your pod or replication controller yaml json files add the pod IP as an environment variable by adding the config block defined below   the block below additionally makes the name and namespace available to the pod   env  - name  MY POD NAME   valueFrom      fieldRef        fieldPath  metadata name - name  MY POD NAMESPACE   valueFrom      fieldRef        fieldPath  metadata namespace - name  MY POD IP   valueFrom      fieldRef        fieldPath  status podIP   Recreate the pod rc and then try  echo  MY POD IP   also run env to see what else kubernetes provides you with   Cheers

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POD HOST   kubectl get pod  POD NAME --template    status podIP      This command will return you an IP

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Some clarifications  not really an answer   In kubernetes  every pod gets assigned an IP address  and every container in the pod gets assigned that same IP address  Thus  as Alex Robinson stated in his answer  you can just use hostname -i inside your container to get the pod IP address   I tested with a pod running two dumb containers  and indeed hostname -i was outputting the same IP address inside both containers  Furthermore  that IP was equivalent to the one obtained using kubectl describe pod from outside  which validates the whole thing IMO   However  PiersyP s answer seems more clean to me   Sources  From kubernetes docs      The applications in a pod all use the same network namespace  same IP and port space   and can thus    find    each other and communicate using localhost  Because of this  applications in a pod must coordinate their usage of ports  Each pod has an IP address in a flat shared networking space that has full communication with other physical computers and pods across the network    Another piece from kubernetes docs      Until now this document has talked about containers  In reality  Kubernetes applies IP addresses at the Pod scope - containers within a Pod share their network namespaces - including their IP address  This means that containers within a Pod can all reach each other   s ports on localhost

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Even simpler to remember than the sed approach is to use awk   Here is an example  which you can run on your local machine   kubectl describe pod   lt podName gt     grep IP   awk   print  2     The IP itself is on column 2 of the output  hence  2

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kubectl get pods -o wide   Give you a list of pods with name  status  ip  node

[kubernetes] How to know a Pod's own IP address from inside a container in the Pod?

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