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nixos/docs/beszel.md
beatzaplentyandClaude Sonnet 4.6 f22ff7db79
Check NixOS configurations / eval-hosts (pull_request) Successful in 10m59s
refactor(beszel): move KEY and TOKEN fully into enable-agent.nix
KEY (hub's SSH public key) is now stored in variables.nix as beszelHubKey
and set by enable-agent.nix — no host file ever needs to touch it.
TOKEN was already universal; this removes the last per-host beszel config.

Importing enable-agent.nix in a build type is now the only step needed to
add a new host to beszel monitoring.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-07-29 12:37:54 +10:00

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Markdown

# Beszel agent
[Beszel](https://github.com/henrygd/beszel) is the monitoring dashboard used
in this LAN. The hub runs as a Docker container on `docker.sweet.home` (port
`vars.ports.beszelHub`, 8090). Each monitored NixOS host runs a
`beszel-agent` that connects back to the hub.
---
## How it works
Everything is handled by a single module:
**`modules/beszel/enable-agent.nix`** — imported by a build type. It:
- Enables `beszel-agent`
- Sets `HUB_URL` to `docker.sweet.home:8090`
- Sets `KEY` from `vars.beszelHubKey` (`variables.nix`) — the hub's SSH
public key, shared by every agent. Update `beszelHubKey` if the docker
host is ever rebuilt and the hub generates a new keypair.
- Reads the universal `beszel-token` from `secrets/common.yaml` via sops
and passes it to the agent as `TOKEN` in an env file
- Fixes an upstream bug where the agent couldn't persist its hub-pairing
fingerprint across restarts (adds a real `StateDirectory`)
A host file needs no beszel configuration at all — just import the module
in the build type and add the system in the hub UI.
---
## Adding beszel to a new build type
Add `../beszel/enable-agent.nix` to the `imports` list in
`modules/build-types/<type>.nix`:
```nix
imports = [
../beszel/enable-agent.nix
# ... other imports
];
```
That's the only change required. The host file needs nothing.
---
## Adding a new system to the hub
1. Rebuild and deploy the host with its build type importing `enable-agent.nix`.
2. Open the beszel hub (`http://docker.sweet.home:8090`).
3. Go to **Systems → Add system**, enter the host's IP and the default port
(45876). The agent will connect and the system will appear as active.
---
## One-time setup: add the token to `secrets/common.yaml`
The universal token is stored once in the common secrets file, shared by all
agents. Only needed once, not per-host:
```sh
sops secrets/common.yaml
```
Add:
```yaml
beszel-token: <token from the beszel hub Settings → Keys>
```
`secrets/common.yaml` is already a sops recipient for every host via their
SSH host keys, so no additional sops recipient setup is needed.
---
## Optional: monitoring extra filesystems
To report disk usage for a mount beyond the root filesystem, add
`EXTRA_FILESYSTEMS` in the host file:
```nix
services.beszel.agent.environment = {
EXTRA_FILESYSTEMS = "/mnt/data"; # colon-separated for multiple paths
};
```
The `server` host uses this to expose its ZFS data pool:
```nix
services.beszel.agent.environment = {
EXTRA_FILESYSTEMS = "${vars.storageRoot}/${vars.nfsShares.dockerVolumes.subpath}";
LOG_LEVEL = "debug";
};
```
---
## Optional: monitoring Docker containers
`enable-agent.nix` has a commented-out line for Docker monitoring:
```nix
#DOCKER_HOST = "tcp://docker-socket-proxy:2375";
```
Uncomment it if the host runs docker-socket-proxy and you want per-container
stats. Hosts without Docker should leave it commented out.
---
## If the hub key changes
If the docker host is ever rebuilt and beszel generates a new SSH keypair,
update `beszelHubKey` in `variables.nix` and rebuild all beszel-enabled hosts.
The new key is visible in the beszel hub under **Settings → Keys**.