nixos-and-flakes-book/docs/en/nixos-with-flakes/update-the-system.md

Updating the System

With Flakes, updating the system is straightforward. Simply execute the following commands in /etc/nixos or any other location where you keep the configuration:

Note

: The /etc/nixos directory is owned by and only writable to root. Therefore, if your flake is located in this directory, you'll need to use sudo to update any configuration files.

# Update flake.lock
nix flake update

# Or update only the specific input, such as home-manager:
nix flake update home-manager

# Apply the updates
sudo nixos-rebuild switch
# Or if your flake is not located at /etc/nixos
sudo nixos-rebuild switch --flake /path/to/flake

# Or to update flake.lock & apply with one command (i.e. same as running "nix flake update" before)
sudo nixos-rebuild switch --recreate-lock-file

Occasionally, you may encounter a "sha256 mismatch" error when running nixos-rebuild switch. This error can be resolved by updating flake.lock using nix flake update.