How to Rollback Changes¶

System Manager keeps track of previous configurations as "generations." If something goes wrong after applying a new configuration, you can rollback to a previous working state.

List Available Generations¶

See all available generations:

sudo nix-env --profile /nix/var/nix/profiles/system-manager-profiles --list-generations

Rollback to the Previous Generation¶

Quickly revert to the last working configuration:

# Switch to the previous generation
sudo nix-env --profile /nix/var/nix/profiles/system-manager-profiles --rollback

# Activate the rollback
nix run 'github:numtide/system-manager' -- activate --sudo

Rollback to a Specific Generation¶

To rollback to a specific generation number:

# Switch to generation 42
sudo nix-env --profile /nix/var/nix/profiles/system-manager-profiles --switch-generation 42

# Activate it
nix run 'github:numtide/system-manager' -- activate --sudo

Cleaning Up Old Generations¶

Over time, old generations consume disk space. Remove them with:

# Remove all old generations (keeps current)
sudo nix-env --profile /nix/var/nix/profiles/system-manager-profiles --delete-generations old

# Run garbage collection to reclaim space
sudo nix-collect-garbage -d

Keeping Recent Generations¶

To keep the last N generations instead of deleting all old ones, use +N. For example, to keep the last 5 generations:

sudo nix-env --profile /nix/var/nix/profiles/system-manager-profiles --delete-generations +5