# nix-cache architecture

This repository configures `nix-cache` as a **binary cache server** and a **remote builder** for other hosts.

## Important design notes

- This is **not** a shared `/nix/store` setup.
- Every machine still keeps and uses its own local `/nix/store`.
- Clients prefer `http://nix-cache` for substitutes and keep `https://cache.nixos.org/` as fallback.
- Clients can offload builds to `nix-cache` through SSH (`nix.distributedBuilds`).

## Binary cache signing keys (on nix-cache)

```bash
sudo install -d -m 0700 /etc/nix
sudo nix-store --generate-binary-cache-key nix-cache-1   /etc/nix/cache-priv.pem   /etc/nix/cache-pub.pem
sudo chmod 0600 /etc/nix/cache-priv.pem
sudo chmod 0644 /etc/nix/cache-pub.pem
cat /etc/nix/cache-pub.pem
```

Do not commit private keys.

## Remote builder SSH keys

On each client, install the private key used to authenticate as `nixremote`:

```bash
sudo install -d -m 0700 /root/.ssh
sudo install -m 0600 ./nixremote /root/.ssh/nixremote
sudo ssh -i /root/.ssh/nixremote nixremote@nix-cache nix-store --version
```

On `nix-cache`, install the matching public key used by `nixremote` authorized keys.

## Manual verification

After deployment:

```bash
curl http://nix-cache/nix-cache-info
nix store ping --store http://nix-cache
nix show-config | grep -E 'substituters|trusted-public-keys|builders-use-substitutes'
sudo ssh -i /root/.ssh/nixremote nixremote@nix-cache nix-store --version
nix build nixpkgs#hello --builders 'ssh://nixremote@nix-cache x86_64-linux /root/.ssh/nixremote 4 2 big-parallel,kvm,nixos-test,benchmark' -L
nix path-info -r nixpkgs#hello
curl -I "http://nix-cache/$(basename "$(nix path-info nixpkgs#hello)").narinfo"
```