This repository contains early experimental tooling for working with concepts of Ubuntu Core 20. Core 20 will ship around April 2020 and will feature a new recovery system and full disk encryption.
This repository contains extremely early prototype for a piece of code that runs in the initial ram disk (initramfs), responsible for performing boot mode selection and setting up initial mount namespace.
At the heart of the recovery is a new partitioning scheme. The existing "writable" partition is accompanied by a new, yet officially unnamed, "systems" partition. The systems partition contains sets of (base, kernel, gadget, snapd) snaps, any of which can be selected at boot using the platform native bootloader.
The system will differentiate RUN mode, which is similar to what Ubuntu Core systems did since the 16 release from RECOVERY modes. In the RUN mode a most-recent set of snaps is used and the system boots normally, unlocking access to the writable partition and the data stored therein.
In the RECOVERY mode access to the writable partition is retained but the partition can be also wiped and re-created, from the set of snaps stored in the systems partition.
This design can be expanded to create additional sub-modes of RECOVERY, where certain data is retained while other data is reset, but the general idea stands.
To work with this repository you will need snap, make, uuidgen, sdisk,
grub2-editenv, qemu-system-x86_64 as well as the ovmf UEFI firmware for
qemu. The snap command is only used to download the pc-kernel snap. Having
done this (the results can be safely cached) builds are entirely offline.
Reading the Makefile is recommended as it explains many things in greater
detail.
The build system is highly parallel and incremental, being able to build a bootable hard disk image under ten seconds. Subsequent changes to files in the repository trigger incremental rebuilds, supporting very fast, offline iteration.
There is no support for testing yet, though a rudimentary set of tests, both unit and integration, is planned soon.
The experiments stages a disk image consisting of EFI-only (legacy mode is not supported yet) GRUB boot loader, using an embedded configuration file to run a kernel and initrd coming from the pc-kernel snap. The initramfs is augmented with an all new snapd-initrd-boot executable, that drives the early boot process.
In the experiment it spawns shell, in the final design it will pass on to the real init system.