Updating & Rollback

Marchyo is a NixOS flake, so updating and rolling back use the standard Nix machinery — there is no bespoke updater or “update channel” to manage. Every nixos-rebuild switch builds a new generation you can boot back into if something breaks.

The short way: the marchyo CLI

The marchyo CLI wraps the whole loop:

marchyo update      # nix flake update in your flake
marchyo upgrade     # update inputs, then rebuild
marchyo rollback    # switch back to the previous generation
marchyo gc          # collect old generations (default: older than 14d)
marchyo diff        # what changed between generations

Update your system

Bump the pinned inputs (including marchyo itself), then rebuild:

# In the directory holding your flake.nix
nix flake update            # bump every input to its latest
# or bump just Marchyo:
nix flake update marchyo

sudo nixos-rebuild switch --flake .#yourhost

On macOS use darwin-rebuild switch --flake .#yourhost instead.

Note

nix flake update rewrites flake.lock. Commit the updated lock file so the change is reproducible and reviewable — the lock is the single source of truth for what your system is built from.

What “update” actually moves

Marchyo’s builders pick the package set for you, so an update tracks different channels depending on the system (see the Introduction):

• Linux and aarch64-darwin ride nixpkgs unstable.
• x86_64-darwin is pinned to stable nixos-26.05 (the last release supporting Intel macOS).

You do not add a separate nixpkgs input — updating the marchyo input is what advances your packages.

Roll back

If a rebuild misbehaves, roll back to the previous generation:

sudo nixos-rebuild switch --rollback

Or pick any earlier generation from the boot menu (systemd-boot / GRUB) at startup — each generation is a separate boot entry. To inspect or prune them:

sudo nix-env --list-generations --profile /nix/var/nix/profiles/system
sudo nix-collect-garbage -d      # remove old generations + free the store

Note

Unlike Btrfs snapshot systems, NixOS generations capture the system closure, not your home files. ~ is untouched by a rollback. Roll back to undo a broken system change; use your own backups for personal data.

Developing on the Marchyo repo itself

If you have a checkout of Marchyo (rather than consuming it as an input), use the just recipes — just update bumps the flake inputs and re-syncs devenv.lock to the same nixpkgs revision, and just verify checks they stay aligned:

just update    # nix flake update + sync devenv.lock
just verify    # confirm flake.lock and devenv.lock agree
just check     # nix flake check (evaluation tests)