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Chapter 45. Introduction to Nmstate

Nmstate is a declarative network manager API. The nmstate package provides the libnmstate Python library and a command-line utility, nmstatectl, to manage NetworkManager on RHEL. When you use Nmstate, you describe the expected networking state using YAML or JSON-formatted instructions.

Nmstate has many benefits. For example, it:

  • Provides a stable and extensible interface to manage RHEL network capabilities
  • Supports atomic and transactional operations at the host and cluster level
  • Supports partial editing of most properties and preserves existing settings that are not specified in the instructions
  • Provides plug-in support to enable administrators to use their own plug-ins

45.1. Using the libnmstate library in a Python application

The libnmstate Python library enables developers to use Nmstate in their own application

To use the library, import it in your source code: 

import libnmstate

Note that you must install the nmstate package to use this library.

Example 45.1. Querying the network state using the libnmstate library

The following Python code imports the libnmstate library and displays the available network interfaces and their state: 

import json
import libnmstate
from libnmstate.schema import Interface

net_state = libnmstate.show()
for iface_state in net_state[Interface.KEY]:
    print(iface_state[Interface.NAME] + ": "
          + iface_state[Interface.STATE])

45.2. Updating the current network configuration using nmstatectl

You can use the nmstatectl utility to store the current network configuration of one or all interfaces in a file. You can then use this file to:

  • Modify the configuration and apply it to the same system.
  • Copy the file to a different host and configure the host with the same or modified settings.

For example, you can export the settings of the enp1s0 interface to a file, modify the configuration, and apply the settings to the host.

Prerequisites

  • The nmstate package is installed.

Procedure

  1. Export the settings of the enp1s0 interface to the ~/network-config.yml file: 

    # nmstatectl show enp1s0 > ~/network-config.yml

    This command stores the configuration of enp1s0 in YAML format. To store the output in JSON format, pass the --json option to the command.

    If you do not specify an interface name, nmstatectl exports the configuration of all interfaces.

  2. Modify the ~/network-config.yml file using a text editor to update the configuration.

  3. Apply the settings from the ~/network-config.yml file: 

    # nmstatectl apply ~/network-config.yml

    If you exported the settings in JSON format, pass the --json option to the command.

45.3. Network states for the network RHEL System role

The network RHEL system role supports state configurations in playbooks to configure the devices. For this, use the network_state variable followed by the state configurations.

Benefits of using the network_state variable in a playbook:

  • Using the declarative method with the state configurations, you can configure interfaces, and the NetworkManager creates a profile for these interfaces in the background.
  • With the network_state variable, you can specify the options that you require to change, and all the other options will remain the same as they are. However, with the network_connections variable, you must specify all settings to change the network connection profile.

For example, to create an Ethernet connection with dynamic IP address settings, use the following vars block in your playbook:

Playbook with state configurations

Regular playbook 

vars:
  network_state:
    interfaces:
    - name: enp7s0
      type: ethernet
      state: up
      ipv4:
        enabled: true
        auto-dns: true
        auto-gateway: true
        auto-routes: true
        dhcp: true
      ipv6:
        enabled: true
        auto-dns: true
        auto-gateway: true
        auto-routes: true
        autoconf: true
        dhcp: true
 
vars:
  network_connections:
    - name: enp7s0
      interface_name: enp7s0
      type: ethernet
      autoconnect: yes
      ip:
        dhcp4: yes
        auto6: yes
      state: up

For example, to only change the connection status of dynamic IP address settings that you created as above, use the following vars block in your playbook:

Playbook with state configurations

Regular playbook 

vars:
  network_state:
    interfaces:
    - name: enp7s0
      type: ethernet
      state: down
 
vars:
  network_connections:
    - name: enp7s0
      interface_name: enp7s0
      type: ethernet
      autoconnect: yes
      ip:
        dhcp4: yes
        auto6: yes
      state: down

Additional resources

  • /usr/share/ansible/roles/rhel-system-roles.network/README.md file

45.4. Additional resources

  • /usr/share/doc/nmstate/README.md
  • /usr/share/doc/nmstate/examples/