Editing CCU:Perstistent storage on the Kubernetes cluster (section)

== Reading/writing to the directories in the pod ==

After you have created the access pod with "kubectl apply -f <filename>.yaml", you have several options to get data to and from the container.

=== Copying data from within the container ===

You can get a root shell inside the container as usual (insert the correct pod name you used below):

<syntaxhighlight lang="yaml">
> kubectl exec -it access-pod -- /bin/bash
</syntaxhighlight>

Your pod has internet access. Thus, an option to get data to/from the pod, in particular into the persistent volume, is to use scp, which first might need to be installed inside the pod:

<syntaxhighlight lang="yaml">
# apt-get update && apt install openssh-client rsync
# cd /my-pvc-mount-path
# scp your.username@external-server:/path/to/data/. ./
</syntaxhighlight>

An even better variant would be "rsync -av" instead of scp, as this only copies files which are different or do not exist in the destination. By reversing source and destination, you can also copy data out of the container this way.

=== Copying data from your local machine ===

From the local machine which has kubectl access to the cluster, you can directly copy data to and from the container using kubectl cp, which has a very similar syntax as scp:

<syntaxhighlight lang="yaml">
# to get data into the container, substitute name with correct id obtained from kubectl get pods
> kubectl cp /path/to/data/. pvc-access-pod:/my-pvc-mount/path/data
# to get data from the container
> kubectl cp pvc-access-pod:/my-pvc-mount/path/. /path/to/output/
</syntaxhighlight>

Read up on Kubernetes "kubectl cp" documentation to check how it handles directories, it's a bit unusual and slightly different from scp.

Note: kubectl cp internally uses tar and some compression to speed up network transfer. However, this means that your access pod needs a certain amount of memory,
in particular when transferring large files. If you run into "error 137" (out of memory), increase memory limits of the access pod or use scp from within the pod.