How to make /etc writable inside user namespace for kubelet in userns

Question

In the kubernetes documentation for running kubelet in user namespace, https://kubernetes.io/docs/tasks/administer-cluster/kubelet-in-userns/, one of the requirements is:

At least, the following directories need to be writable in the namespace (not outside the namespace):

/etc

How can this be achieved in a user namespace?

Answer 1

The part of the documentation right above where you quoted explains that:

After unsharing the user namespace, you will also have to unshare other namespaces such as mount namespace.

You do not need to call chroot() nor pivot_root() after unsharing the mount namespace, however, you have to mount writable filesystems on several directories in the namespace.