Accessing Logs and Investigating Container Restarts in Kubernetes

![](https://4.bp.blogspot.com/-BI3zOVlrHwA/Vxf0KwcqtCI/AAAAAAAAAbw/vzv8X8vQrso9Iycx4qQHuOslE8So7smLgCLcB/s400/27gf-counter.png)](https://4.bp.blogspot.com/-BI3zOVlrHwA/Vxf0KwcqtCI/AAAAAAAAAbw/vzv8X8vQrso9Iycx4qQHuOslE8So7smLgCLcB/s1600/27gf-counter.png) When the pod status changes to Running we can use the kubectl logs command to view the output of this counter pod. ``` $ kubectl logs counter 0: Tue Jun 2 21:37:31 UTC 2015 1: Tue Jun 2 21:37:32 UTC 2015 2: Tue Jun 2 21:37:33 UTC 2015 3: Tue Jun 2 21:37:34 UTC 2015 4: Tue Jun 2 21:37:35 UTC 2015 5: Tue Jun 2 21:37:36 UTC 2015 ``` This command fetches the log text from the Docker log file for the image that is running in this container. We can connect to the running container and observe the running counter bash script. ``` bash $ kubectl exec -i counter bash ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 17976 2888 ? Ss 00:02 0:00 bash -c for ((i = 0; ; i++)); do echo "$i: $(date)"; sleep 1; done root 468 0.0 0.0 17968 2904 ? Ss 00:05 0:00 bash root 479 0.0 0.0 4348 812 ? S 00:05 0:00 sleep 1 root 480 0.0 0.0 15572 2212 ? R 00:05 0:00 ps aux ``` What happens if for any reason the image in this pod is killed off and then restarted by Kubernetes? Will we still see the log lines from the previous invocation of the container followed by the log lines for the started container? Or will we lose the log lines from the original container’s execution and only see the log lines for the new container? Let’s find out. First let’s stop the currently running counter. ``` $ kubectl stop pod counter pods/counter Now let’s restart the counter. $ kubectl create -f counter-pod.yaml pods/counter ``` Let’s wait for the container to restart and get the log lines again. ``` $ kubectl logs counter 0: Tue Jun 2 21:51:40 UTC 2015 1: Tue Jun 2 21:51:41 UTC 2015 2: Tue Jun 2 21:51:42 UTC 2015 3: Tue Jun 2 21:51:43 UTC 2015 4: Tue Jun 2 21:51:44 UTC 2015 5: Tue Jun 2 21:51:45 UTC 2015

This section illustrates how to access the logs of a running pod using 'kubectl logs' and how to execute commands inside the container using 'kubectl exec'. It then explores the behavior of logs when a container within a pod is stopped and restarted, demonstrating that the logs from the previous container instance are not retained by default. The user stops the pod and restarts it to verify the log behavior.