Kubernetes Docker logs

Question

I'm trying to check kubernetes logs on docker, using the following command:

kubectl logs pod_name -n namespace

it prints all the logs from the start

1. Is there anyway to tail the logs or check logs between the given window?
2. Is it possible to rotate docker logs based on size or date?

Answer 1

1) yes, you can tail or filter by date.

As easy as running

kubectl logs --help
Options:
  -c, --container='': Print the logs of this container
  -f, --follow=false: Specify if the logs should be streamed.
      --include-extended-apis=true: If true, include definitions of new APIs via calls to the API server. [default true]
      --interactive=false: If true, prompt the user for input when required.
      --limit-bytes=0: Maximum bytes of logs to return. Defaults to no limit.
      --pod-running-timeout=20s: The length of time (like 5s, 2m, or 3h, higher than zero) to wait until at least one
pod is running
  -p, --previous=false: If true, print the logs for the previous instance of the container in a pod if it exists.
  -l, --selector='': Selector (label query) to filter on.
      --since=0s: Only return logs newer than a relative duration like 5s, 2m, or 3h. Defaults to all logs. Only one of
since-time / since may be used.
      --since-time='': Only return logs after a specific date (RFC3339). Defaults to all logs. Only one of since-time /
since may be used.
      --tail=-1: Lines of recent log file to display. Defaults to -1 with no selector, showing all log lines otherwise
10, if a selector is provided.
      --timestamps=false: Include timestamps on each line in the log output

2) Docker stores the container logs in host in the path /var/lib/docker/containers/{ContainerId} so you could copy/truncate the logs directly.

Answer 2

To tail the logs, use the -foption

kubectl logs pod_name -n namespace -f

You can query logs x-lines ago or since a time range. Take a look at the —tail and —since options