Introduction

Distribution installers, cloud instantiation, image builds for particular devices, or any other way to deploy an operating system put its desired network configuration into YAML configuration file(s). During early boot, the netplan "network renderer" runs which reads /{lib,etc,run}/netplan/*.yaml and writes configuration to /run to hand off control of devices to the specified networking daemon.

General structure

netplan's configuration files use the YAML format. All /{lib,etc,run}/netplan/*.yaml are considered. Lexicographically later files (regardless of in which directory they are) amend (new mapping keys) or override (same mapping keys) previous ones. A file in /run/netplan completely shadows a file with same name in /etc/netplan, and a file in either of those directories shadows a file with the same name in /lib/netplan.

The top-level node in a netplan configuration file is a network: mapping that contains version: 2 (the YAML currently being used by curtin, MaaS, etc. is version 1), and then device definitions grouped by their type, such as ethernets:, wifis:, or bridges:. These are the types that our renderer can understand and are supported by our backends.

Each type block contains device definitions as a map where the keys (called "configuration IDs") are defined as below.

Device configuration IDs

The key names below the per-device-type definition maps (like ethernets:) are called "ID"s. They must be unique throughout the entire set of configuration files. Their primary purpose is to serve as anchor names for composite devices, for example to enumerate the members of a bridge that is currently being defined.

There are two physically/structurally different classes of device definitions, and the ID field has a different interpretation for each:

Physical devices

(Examples: ethernet, wifi) These can dynamically come and go between reboots and even during runtime (hotplugging). In the generic case, they can be selected by match: rules on desired properties, such as name/name pattern, MAC address, driver, or device paths. In general these will match any number of devices (unless they refer to properties which are unique such as the full path or MAC address), so without further knowledge about the hardware these will always be considered as a group.

It is valid to specify no match rules at all, in which case the ID field is simply the interface name to be matched. This is mostly useful if you want to keep simple cases simple, and it's how network device configuration has been done for a long time.

If there are match: rules, then the ID field is a purely opaque name which is only being used for references from definitions of compound devices in the config.

Virtual devices

(Examples: veth, bridge, bond) These are fully under the control of the config file(s) and the network stack. I. e. these devices are being created instead of matched. Thus match: and set-name: are not applicable for these, and the ID field is the name of the created virtual device.

Common properties for physical device types

match (mapping)

This selects a subset of available physical devices by various hardware properties. The following configuration will then apply to all matching devices, as soon as they appear. All specified properties must match.

name (scalar)
Current interface name. Globs are supported, and the primary use case for matching on names, as selecting one fixed name can be more easily achieved with having no match: at all and just using the ID (see above). Note that currently only networkd supports globbing, NetworkManager does not.
macaddress (scalar)
Device's MAC address in the form "XX:XX:XX:XX:XX:XX". Globs are not allowed.
driver (scalar)
Kernel driver name, corresponding to the DRIVER udev property. Globs are supported. Matching on driver is only supported with networkd.

Examples:

set-name (scalar)

When matching on unique properties such as path or MAC, or with additional assumptions such as "there will only ever be one wifi device", match rules can be written so that they only match one device. Then this property can be used to give that device a more specific/desirable/nicer name than the default from udev’s ifnames. Any additional device that satisfies the match rules will then fail to get renamed and keep the original kernel name (and dmesg will show an error).

wakeonlan (bool)

Enable wake on LAN. Off by default.

Common properties for all device types

renderer (scalar)

Use the given networking backend for this definition. Currently supported are networkd and NetworkManager. This property can be specified globally in networks:, for a device type (in e. g. ethernets:) or for a particular device definition. Default is networkd.

dhcp4 (bool)

Enable DHCP for IPv4. Off by default.

dhcp6 (bool)

Enable DHCP for IPv6. Off by default.

addresses (sequence of scalars)

Add static addresses to the interface in addition to the ones received through DHCP or RA. Each sequence entry is in CIDR notation, i. e. of the form addr/prefixlen. addr is an IPv4 or IPv6 address as recognized by inet_pton(3) and prefixlen the number of bits of the subnet.

Example: addresses: [192.168.14.2/24, 2001:1::1/64]

gateway4, gateway6 (scalar)

Set default gateway for IPv4/6, for manual address configuration. This requires setting addresses too. Gateway IPs must be in a form recognized by inet_pton(3).

Example for IPv4: gateway4: 172.16.0.1
Example for IPv6: gateway6: 2001:4::1

nameservers (mapping)

Set DNS servers and search domains, for manual address configuration. There are two supported fields: addresses: is a list of IPv4 or IPv6 addresses similar to gateway*, and search: is a list of search domains.

Example:

ethernets:
  id0:
    [...]
    nameservers:
      search: [lab, home]
      addresses: [8.8.8.8, FEDC::1]

Properties for device type ethernets:

Ethernet device definitions do not support any specific properties beyond the common ones described above.

Properties for device type wifis:

Note that systemd-networkd does not natively support wifi, so you need wpasupplicant installed if you let the networkd renderer handle wifi.

access-points (mapping)

This provides pre-configured connections to NetworkManager. Note that users can of course select other access points/SSIDs. The keys of the mapping are the SSIDs, and the values are mappings with the following supported properties:

password (scalar)
Enable WPA2 authentication and set the passphrase for it. If not given, the network is assumed to be open. Other authentication modes are not currently supported.
mode (scalar)
Possible access point modes are infrastructure (the default), ap (create an access point to which other devices can connect), and adhoc (peer to peer networks without a central access point). ap is only supported with NetworkManager.

Properties for device type bridges: and bonds:

interfaces (sequence of scalars)

All devices matching this ID list will be added to the bridge/bond.

Example:

  ethernets:
    switchports:
      match: {name: "enp2*"}
  [...]
  bridges:
    br0:
      interfaces: [switchports]

Properties for device type vlans:

id (scalar)

VLAN ID, a number between 0 and 4094.

link (scalar)

netplan ID of the underlying device definition on which this VLAN gets created.

Example:

ethernets:
  eno1: {...}
vlans:
  en-intra:
    id: 1
    link: eno1
    dhcp4: yes
  en-vpn:
    id: 2
    link: eno1
    address: ...

Examples

Configure an ethernet device with networkd, identified by its name, and enable DHCP:

network:
  version: 2
  ethernets:
    eno1:
      dhcp4: true

This is a complex example which shows most available features:

network:
  version: 2
  # if specified, can only realistically have that value, as networkd cannot
  # render wifi/3G.
  renderer: NetworkManager
  ethernets:
    # opaque ID for physical interfaces, only referred to by other stanzas
    id0:
      match:
        macaddress: 00:11:22:33:44:55
      wakeonlan: true
      dhcp4: true
      addresses:
        - 192.168.14.2/24
        - 2001:1::1/64
      gateway4: 192.168.14.1
      gateway6: 2001:1::2
      nameservers:
        search: [foo.local, bar.local]
        addresses: [8.8.8.8]
    lom:
      match:
        driver: ixgbe
      # you are responsible for setting tight enough match rules
      # that only match one device if you use set-name
      set-name: lom1
      dhcp6: true
    switchports:
      # all cards on second PCI bus; unconfigured by themselves, will be added
      # to br0 below
      match:
        name: enp2*
      mtu: 1280
  wifis:
    all-wlans:
      # useful on a system where you know there is only ever going to be one device
      match: {}
      access-points:
        "Joe's home":
          # mode defaults to "managed" (client)
          password: "s3kr1t"
    # this creates an AP on wlp1s0 using hostapd; no match rules, thus ID is
    # the interface name
    wlp1s0:
      access-points:
        "guest":
           mode: ap
           channel: 11
           # no WPA config implies default of open
  bridges:
    # the key name is the name for virtual (created) interfaces; no match: and
    # set-name: allowed
    br0:
      # IDs of the components; switchports expands into multiple interfaces
      interfaces: [wlp1s0, switchports]
      dhcp4: true
  routes:
   - to: 0.0.0.0/0
     via: 11.0.0.1
     metric: 3