#import "@preview/polylux:0.4.0": *
#import "@preview/metropolis-polylux:0.1.0" as metropolis

#show: metropolis.setup
#show: metropolis.setup.with(footer: [NixOS on routers])

#slide[
  #set page(header: none, footer: none, margin: 3em)

  #text(size: 1.3em)[*NixOS on routers*]

  Fosdem 2026

  #metropolis.divider

  #set text(size: .8em, weight: "light")
  Karel Kočí

  31.01.2026
]

#metropolis.new-section[Why?]

#slide[
= Why?

#toolbox.side-by-side[
- Unified deployment
- Unified management
- Unified monitoring
- Unified tools
][
#set align(center)
#image("unified.png")
]
- Reproducible
]

#slide[
  #set page(header: none, footer: none, margin: 0em)

  #set align(center)
  #grid(
    columns: (50%, 50%),
    rows: (47%, 53%),
    image("omnia.jpg"),
    image("mox.jpg"),
    image("ssh-omnia.png"),
    image("ssh-mox.png"),
  )
]

#metropolis.new-section[Network Setup]

#slide[
= SystemD Networkd
#set text(18pt)
```nix
boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = 1;
networking.useNetworkd = true;
systemd.network = {
  "eth1" = {
    matchConfig.Name = "eth1";
    networkConfig = {
      Address = "192.168.1.1/24";
      IPv4Forwarding = "yes"; DHCPServer = "yes"; DHCPPrefixDelegation = "yes";
      IPv6Forwarding = "yes"; IPv6SendRA = "yes"; IPv6AcceptRA = "no";
    };
    dhcpServerConfig = {
        UplinkInterface = "eth0";
        PoolOffset = 100; PoolSize = 100;
    };
    dhcpPrefixDelegationConfig = {
      UplinkInterface = "eth0"; SubnetId = 1; Announce = "yes";
    };
  };
};
```
]

#slide[
= Resolved
#set text(18pt)
```nix
services.resolved = {
  enable = true;
  settings.Resolve = {
    DNSStubListenerExtra=["192.168.1.1"];
    FallbackDNS = ["1.1.1.1" "8.8.8.8"];
  };
};

systemd.network."eth1".dhcpServerConfig = {
  EmitDNS = "yes";
  DNS = "192.168.1.1";
};
```
]

#slide[
= Firewall
#set text(18pt)
```nix
networking.firewall = {
  interfaces."eth1".allowedUDPPorts = [
    53 67 68
  ];

  nat = {
    enable = true;
    externalInterface = "eth0";
    internalInterfaces = ["eth1"];
  };
};
```
]

#metropolis.new-section[Choosing Hardware]

#slide[
= Hardware Requirements

- 2-\? Ethernet interfaces
- Wi-Fi?
- Storage (NixOS at least 16G): NVMe / mSD card
- CPU architecture: Watts vs. support
]

#slide[
= SOHO Router
#set align(top)
Commonly ARMv7l or AArch64.
#toolbox.side-by-side[
== Advantages
- Small form factor
- Lower power consumption
][
== Disadvantages
- Harder to get running
- Requires cross-compilation
- ARMv7l on NixOS is pain
]
]

#slide[
= x84_64 with PCIe cards
#set align(top)
#toolbox.side-by-side[
== Advantages
- Architecture fully supported
- Not different from server
- More powerful for service hosting
][
== Disadvantages
- Possibly higher power consumption
- Large form factor
]

#set align(horizon)
Most likely better paired with SOHO for Wi-Fi and non-NixOS switch.
]

#slide[
= Bonus: Porting to ARM

```nix
nixpkgs.hostPlatform.system = "armv7l-linux";
boot = {
  loader = {
    grub.enable = false;
    systemd-boot.enable = false;
    generic-extlinux-compatible.enable = true;
  };
  kernelPackages = pkgs.linuxPackagesFor pkgs.linux_6_1_turris_omnia;
  initrd.includeDefaultModules = false;
  kernelParams = [ "earlyprintk" "console=ttyS0,115200" ];
  kernelModules = [ "leds_turris_omnia" ];
  initrd.availableKernelModules = [ "ahci_mvebu" "rtc_armada38x" ];
};
```
]

#slide[
  #show: metropolis.focus
  Thank you

  Karel Kočí

  #metropolis.divider

  #text(size: 0.7em)[
    https://gitlab.com/Cynerd/nixos-personal

    https://git.cynerd.cz/presentations/tree/2026-fosdem
  ]
]