Customfs

Customfs is an early boot platform experiment for building a small, custom initramfs that can discover a future Ubuntu base_os root filesystem and fall back to a rescue shell when it is missing or invalid.

The first milestone intentionally does not require an Ubuntu rootfs. It proves that the kernel and initramfs can boot independently and provide a rescue environment.

Initial goal

UEFI/GRUB
  -> Linux kernel from the target server
  -> custom initramfs
  -> look for /dev/disk/by-label/base_os
  -> if missing, drop to rescue shell

Project layout

.
├── AGENT.md
├── Makefile
├── README.md
├── configs/
│   └── default.conf
├── docs/
│   ├── architecture.md
│   ├── layout-v1.md
│   └── roadmap.md
├── initramfs/
│   └── init
└── scripts/
    ├── build-initramfs.sh
    ├── install-deps.sh
    └── install-grub-test-entry.sh

Build on the target server

sudo ./scripts/install-deps.sh
make

The output is written to:

build/initrd-customfs.img

Install a GRUB test entry

sudo ./scripts/install-grub-test-entry.sh
sudo update-grub

Then boot the Customfs initramfs test entry.

Expected first result

Because base_os does not exist yet, the system should stop here:

=== Customfs initramfs ===
ERROR: base_os device not found.
Dropping to rescue shell.
/ #

That is the desired first milestone.