AUVFS

Atomic Upgrade over Virtual Filesystem

TLDR: Usage

git submodule update --init --recursive
make
./auvfs pacman -Syu

Why this matters?

• Common Linux package managers are not ATOMIC
• Non-atomic upgrades can render the system unusable

What do we want?

• An ATOMIC upgrade
• Users observe:
  • Either before the any package upgrade happens
  • Either the upgrade fully completed
  • But never a partially upgraded system

Why not XXX?

• Why not OSTree?
  • rpm-ostree is great, but I'm using Arch :-(
• Why not btrfs / zfs?
  • They are great too. But I'm using ext4 on my root partition :-(

How it works?

• It is divided to 3-phases:
  • Apply: build an full and working out-of-root tree, using hardlinks and symlinks
  • Commit: use rename to commit, as it is (almost) atomic.
  • Finalize: fix remaining symlinks
• As long as the Commit phase is atomic, your system won't brick.
• Q: That's still not atomic, you commit /usr etc. separately!
  • A: You're right. If we can get everything under /usr, it will work.