Rootfs image builder

This repo builds an ext4 or an initrd using Docker containers.

Note: some assembly required.

Prerequisites

Your user needs to be able to run docker.

If not, run scripts with sudo: sudo build-rootfs.sh.

Building a rootfs

Simply run:

./build-rootfs.sh <rootfs-type>

Where rootfs-type is one of the root filesystem generators that starts with type-.

For example, to generate an Ubuntu 21.04 rootfs, run:

./build-rootfs.sh ubuntu21.04

Note: By default, all images are generated as sparse files.

Building an initrd

The initrd is built using ./build-initrd.sh. By default it's based on the alpine image.

Customizing the build process

Each rootfs generator consists of 3 files:

• init-rootfs.sh: creates the root filesystem and formats it. This is needed because a distribution may take a larger amount of space

• inside-container.sh: what is installed in a rootfs. Here this script usually finishes with copying the rootfs contents to a mounted rootfs.ext4 file.

• run-container.sh: controls the container lifetime. For example the Ubuntu container is started twice because systemd needs to be initialized.

Adding a new image type

Just add a new folder with the 3 files described above

Troubleshooting

• Need a larger image? Change init-rootfs.sh.