https://github.com/Nekroze/vms.nix

NixOS module for QEMU VM's using a similar interface to nixos-containers.
https://github.com/Nekroze/vms.nix

Last synced: 3 months ago
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NixOS module for QEMU VM's using a similar interface to nixos-containers.

• Host: GitHub
• URL: https://github.com/Nekroze/vms.nix
• Owner: Nekroze
• Created: 2019-09-01T03:50:57.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2019-09-01T05:11:07.000Z (about 5 years ago)
• Last Synced: 2024-05-31T08:35:41.511Z (6 months ago)
• Language: Nix
• Size: 6.84 KB
• Stars: 33
• Watchers: 5
• Forks: 8
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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README

        
# vms.nix

A [NixOS][1] module that provides [QEMU][2] based virtual machines using a similar

configuration interface to the `containers` [NixOS][1] options.

## Usage

Before proceeding you must first import this module. Simply clone this

repository and place it under `/etc/nixos/` then in your

`/etc/nixos/configuration.nix` add the following imports:

```nix

{

  imports = [

    ./vms.nix

  ];

}

```

### Enabling

Everything this module does can be enabled or disabled with the

`boot.enableVirtualMachines`, so the first step is to set that to true

somewhere in your [NixOS][1] configuration.

```nix

{

  boot.enableVirtualMachines = true;

}

```

If we later set this option to `false` all virtual machines will be stopped and

their services removed, although any data will persist.

### First Virtual Machine

Let's test the waters by starting a dead simple VM that we can remotely connect to:

```nix

{

  boot.enableVirtualMachines = true;

  virtualMachines.guest = {

    autoStart = true;

    config = {

      system.stateVersion = "19.03";

      services.openssh.enable = true;

      users.users.root.openssh.authorizedKeys.keyFiles = [

        /root/.ssh/authorized_keys

      ];

    };

    qemuSwitches = [

      "nic user,hostfwd=tcp::10022-:22"

    ];

  };

}

```

Here we have defined a virtual machine called `guest` that runs `openssh`,

allowing in to root anyone that has been given remote access to the root user

of the [NixOS][1] host machine via the `/root/.ssh/authorized_keys` files.

Finally we add an extra switch to [QEMU][2] to be used when the VM starts that

sets up network forwarding from `localhost:10022` on the host machine to port

`22` in the guest machine.

Now we can run `nixos-rebuild switch` and the VM will come online ready for

connection. First we will check the VM service's status where we should be able

to see the boot log.

```bash

systemctl status vm@guest

```

All `virtualMachines` are managed via a systemd service named `vm@$VM_NAME`. We

can also stop, start, or restart this service.

Before a machine starts (other than its first time) it will attempt to migrate

the backing store of the disk image, this means that the config is deployed

onto a disk image in your `/nix/store` but any changes to the VM once it is

running are stored on the root disk image at

`/var/lib/vms/$VM_NAME.$VM_ROOT_IMAGE_FORMAT` so if we wanted to erase any

state that has built up for the `guest` VM I can delete

`/var/lib/vms/guest.qcow2`. This path can be changed via the

`virtualMachines.guest.rootImagePath` option.

Let's get on with it and get in there, assuming you have a key in

`/root/.ssh/authorized_keys`:

```bash

ssh -p 10022 root@localhost

```

[1]: https://nixos.org/nixos

[2]: https://www.qemu.org/

[3]: https://nixos.org/nix