Adds component troubleshooting

component_troubleshooting.md

+# Component Troubleshooting
+
+Components may fail for different reasons. In this guide, we will show you how to troubleshoot in the kubernetes cluster.
+
+## Table of contents
+- [Accessing the kubernetes cluster](#accessing-the-kubernetes-cluster)
+- [Kubeconfig](#kubeconfig)
+- [Logs](#logs)
+- [Exec](#exec)
+- [Run](#run)
+- [Copy](#copy)
+
+## Accessing the kubernetes cluster
+
+The kubernetes cluster includes a rancher server that allows you to access the kubernetes cluster. The rancher server is available at https://k8so.emerald.digital.tecnalia.dev/. 
+
+![Rancher Welcome Page](.media/image04.png)
+![Rancher Cluster Selection](.media/image05.png)
+
+There you can access the kubernetes cluster and check the deployment of the component.
+
+![Rancher UI](.media/image08.png)
+
+## Kubeconfig
+For troubleshooting in a terminal with kubectl, you need to download the kubeconfig file. 
+
+To get the kubeconfig login into kubernetes https://k8so.emerald.digital.tecnalia.dev/ and download the kubeconfig. **Be aware that the kubeconfig is valid for one month**.
+
+![Kubeconfig Download](.media/image03.png)
+![Kubeconfig deadline](.media/image06.png)
+
+The kubeconfig should be stored in the `~/.kube/config` file. 
+
+```bash
+cat << EOF > ~/.kube/config
+<content of the kubeconfig file>
+EOF
+```
+![alt text](.media/image07.png)
+
+```bash
+kubectl config get-contexts
+kubectl config use-context local
+```
+
+The above is valid for one kubernetes cluster. If you have more than one kubernetes cluster, you can store the kubeconfig in different files and use the `KUBECONFIG` environment variable to select the kubeconfig file.
+
+## Logs
+
+Logs of a pod of a can be accessed using the rancher UI or the kubectl command.
+
+```bash
+kubectl -n emerald-dev logs –f <pod-name>
+```
+
+We can also access using the deployment name.
+
+```bash
+kubectl -n emerald-dev logs –f deployment/<deployment-name> -c <container-name>
+```
+
+## Exec
+
+To check what has inside a container, install packages, curl, nslookup, …
+
+```bash
+kubectl -n emerald-ext exec -it <pod-name>
+ -- /bin/bash
+```
+
+`/bin/bash` is the shell that will be executed in the container. If the container does not have `/bin/bash`, you can try to use `/bin/sh`. This will depend on the base image of the container.
+
+## Run
+
+Sometimes we need to run a container in the same internal network to check services, pods, ports, etc.
+
+```bash
+kubectl -n emerald-ext run -i --tty --rm --image busybox --restart=Never -- /bin/bash
+```
+
+Replace `busybox` with the image you want to run. Remember that the `/bin/bash` is the shell that will be executed in the container. If the container does not have `/bin/bash`, you can try to use `/bin/sh`. This will depend on the base image of the container.
+
+## Copy
+
+To copy files from a container to the local machine, we can use the `kubectl cp` command. This can be handy for backup purposes.
+
+```bash
+kubectl -n emerald-ext cp <pod-name>:<path-in-container> <path-in-local-machine>
+```
+
+For example, to copy the file `/etc/hosts` from the pod `my-pod` to the local machine, we can use the following command:
+
+```bash
+kubectl -n emerald-ext cp my-pod:/etc/hosts /tmp/hosts
+```
+
+You can also copy files from the local machine to the container.
+
+```bash
+kubectl -n emerald-ext cp /tmp/hosts my-pod:/etc/hosts
+```