Cannot run `useradd` command in a container created by nerdctl+kata.

### Description

I cannot run the command `useradd` in my host, as seen below:

For the purpose of learning, I want to create new user in my server. Hence, I use nerdctl + kata container to create a container in rootfull mode. However, in this container, I still cannot run the `useradd` command, as seen below:

So how to fix it? Thank you very much!

### Steps to reproduce the issue

1. run `nerdctl run -it --runtime io.containerd.kata.v2 ubuntu:20.04 sh` to enter a container.
2. run `su` to enter the root mode in the container.
3. execute `useradd`, and then it raises the problem.

### Describe the results you received and expected

I want to have the totally full root authority in my container created by nerdctl + kata.

### What version of nerdctl are you using?

nerdctl: 1.7.5
kata: 3.3.0

### Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

### Host information

_No response_