# Install a node-locked license

```{note}
This page only applies to **commercial use** of ACEMD. Non-commercial use is free and does not require a license file or server — see [License options](../explanation/license-options.md).
```

**You will learn:** how to install a commercial ACEMD node-locked license on a single workstation.

**Prerequisites:**

- A commercial license purchased from Acellera. The license is issued as a `license.dat` file tied to the **MAC address** you provided at purchase.

For an overview of license types (non-commercial, node-locked, floating, cloud), see [License options](../explanation/license-options.md).

## Step 1 — Place the license file

At startup ACEMD checks whether any of these env vars are defined or whether any of these files exist; if **any** of them is present it invokes the bundled `license-checker` binary, which performs the actual validation:

- Env var `$ACELLERA_LICENSE_FILE` (or the British-spelling `$ACELLERA_LICENCE_FILE`).
- `/opt/acellera/license.dat` or `/opt/acellera/licence.dat` — system-wide.
- `~/.acellera/license.dat` or `~/.acellera/licence.dat` — per-user.

Both spellings are accepted at each location. Which license actually gets used when several are present is decided by the bundled checker, not by ACEMD itself. The easiest path is to drop the file in your home directory:

```bash
mkdir -p ~/.acellera
cp license.dat ~/.acellera/license.dat
```

For a multi-user host, put it in `/opt/acellera/license.dat` (readable by all ACEMD users).

## Step 2 — (Optional) Point at a custom location with an env var

If the license lives somewhere else:

```bash
export ACELLERA_LICENSE_FILE=/path/to/license.dat
```

Add the line to your shell rc (`~/.bashrc`, `~/.zshrc`, …) so it survives new shells.

Verify it's set:

```bash
env | grep ACELLERA_LICENSE_FILE
```

## Step 3 — Verify

```bash
acemd --license
```

This runs the bundled license checker and prints its report, which tells you whether a valid license was found. Note that `acemd --license` always exits with status `0` regardless of the result — read the printed output to confirm the install rather than checking the exit code.

## Gotchas

- The license is bound to the **MAC address** of the issuing machine. Moving `license.dat` to a different host fails the validation.
- ACEMD also recognises the British spelling `ACELLERA_LICENCE_FILE` for backward compatibility, but the American spelling is preferred for new installations.

## See also

- [License options](../explanation/license-options.md)
- [Deploy a floating license server](deploy-a-floating-license-server.md)