Removing device nodes breaks MicroVM RootFS setup

[carlvoller]

Hi,

I'm not sure if my use case is an intended use case for minideb, but I currently use minideb to build the base of rootfs images to be used with MicroVMs like Firecracker.

Unfortunately a recent PR #173 breaks my current set up process for building my RootFS images.

It appears that apt-key relied on a /dev/null existing in the minideb tar archive in order to work.

Steps to reproduce the issue:

1. Run make bookworm to get a bookworm.tar
2. Create an empty ext4 file system

dd if=/dev/zero of=rootfs.ext4 bs=1M count=1024
sudo mkfs.ext4 rootfs.ext4

3. Mount the empty ext4 file system and dump the contents of bookworm.tar into the file system

sudo mkdir -p /tmp/debian
sudo mount -o loop rootfs.ext4 /tmp/debian
sudo tar -xvf bookworm.tar -C /tmp/debian/

4. Chroot into the file system to install and setup the bare minimum required to continue setup in the MicroVM.

sudo chroot /tmp/debian /bin/bash

# Inside chroot shell
apt-get update

Describe the results you received:

I now get a number of /dev/null Permission Denied errors and many gpg verification errors.

Describe the results you expected:

By checking out to a commit before #173, the build works as expected with apt-get working as intended.

Additional information you deem important (e.g. issue happens only occasionally):

My kernel version is 5.10.0-33-cloud-amd64 if that helps.

Additional environment details (AWS, VirtualBox, Docker for MAC, physical, etc.):

I am running this on a GCP Compute Engine VM (n2-standard-4) with Nested Virtualisation enabled. I do not have Docker or any other hypervisor installed on this machine other than Qemu installed by Minideb.