Feature request: Add a generic customization layer or allow custom commands in config

[johanehnberg]

To facilitate simpler customization and easier adoption of the tool, I suggest creating a generic customization layer or config extension that can accommodate the most common customization cases. The cases I recognize are:

1. Running commands on target
2. Running commands on host
3. Pushing files to the target

With a built-in customization layer, it could look something like this:

customizer:
  chroot:
  - useradd -m -s /bin/bash -u 4000 $IGconf_device_user1
  command:
  - date > $1/etc/imagetime
  file1source: ../myconf
  file1target: /etc/myconf

If the config file format would accommodate the same directly instead, it could essentially pass through mmdebstrap same as layers:

mmdebstrap:
  customize-hooks:
  - chroot $1 sh -c "useradd -m -s /bin/bash -u 4000 $IGconf_device_user1"
  - date > $1/etc/imagetime
  - cp ../myconf $1/etc/myconf

[Sefran007]

You can take a look at the layer/rpi/user-credentials.yaml file.
I think we need a separate user creation layer...

[johanehnberg]

The useradd case in the issue description serves merely as a command example. The expectation would be that the desired command is something not found in existing layers.