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Network Automation with Nornir

Nornir is a pure-Python automation framework designed for network engineers and operators. It provides an extensible, plugin-driven approach to inventory management, task execution, and parallel device interactions without requiring an external orchestrator or agent on target devices.

Why Nornir?

  • Pythonic Workflow: Everything is native Python—no DSL required.
  • Extensible Plugin System: Swap inventory, connection, and task plugins (Netmiko, Scrapli, Napalm, etc.) without rewriting core logic.
  • Parallelism: Built-in support for executing tasks concurrently across your inventory.
  • Reusability & Testing: Break automation steps into Python functions, importable and testable in isolation.

Core Concepts

  1. Inventory

    • Defines hosts, groups, and defaults.
    • Managed via Inventory plugins (e.g., SimpleInventory, YAMLInventory).

  2. InitNornir

    • Bootstraps the Nornir engine by loading inventory and defaults.

  3. Tasks & Plugins

    • Tasks are Python functions that perform actions on devices (send CLI commands, retrieve telemetry, apply configs).
    • Task Plugins (e.g., nornir_netmiko, nornir_scrapli) provide pre-built tasks like send_command or send_config.

  4. Runner

    • Invokes tasks across hosts, managing concurrency, result aggregation, and error handling.

  5. Results

    • Each task run returns a structured result object (MultiResult), containing per-host Result entries with .result, .failed, and .exception fields.

Example USage

Similar to ansible and netmiko example we will use nornior to do exact same thing! Backing up the nokia router

  1. Register Inventory & Init Nornir: Load your nornir-simple-inventory.yml.
  2. Generate Timestamp: One timestamp for all hosts.
  3. For Each Host (backup_config):
  4. Disable paging (screen-length 0 temporary)
  5. Run bash cat /etc/opt/srlinux/config.json to grab the running config
  6. Save to config__<YYYYMMDD_HHMMSS>.json
  7. Run the Task across all hosts with nr.run(task=backup_config).
#!/usr/bin/env python3
"""
back-nornir.py

Use Nornir + Scrapli to backup SR Linux config with detailed logs.
"""

import datetime
from nornir import InitNornir
from nornir.core.plugins.inventory import InventoryPluginRegister
from nornir.plugins.inventory.simple import SimpleInventory
from nornir_scrapli.tasks import send_command

print("=== Nornir SR Linux Config Backup Script ===")

# 1) Register the SimpleInventory plugin so Nornir can find it by name
print("Registering SimpleInventory plugin...")
InventoryPluginRegister.register("SimpleInventory", SimpleInventory)
print("Plugin registered successfully.\n")

# 2) Create a shared timestamp for all output files
ts = datetime.datetime.now().strftime("%Y%m%d_%H%M%S")
print(f"Timestamp for this run: {ts}\n")

# 3) Initialize Nornir, pointing at your existing inventory file
inventory_file = "/home/netopschic/Documents/practicals/clab/clab-srlceos01/nornir-simple-inventory.yml"
print(f"Initializing Nornir using inventory file:\n  {inventory_file}\n")
nr = InitNornir(
    inventory={
        "plugin": "SimpleInventory",
        "options": {
            "host_file": inventory_file,
        },
    }
)
print("Nornir initialization complete.\n")

def backup_config(task):
    print(f"[{task.host.name}] ➤ Starting backup task")

    # 4) Disable paging so the device streams the full output
    print(f"[{task.host.name}] ➤ Disabling paging...")
    task.run(task=send_command, command="screen-length 0 temporary")
    print(f"[{task.host.name}] ✓ Paging disabled")

    # 5) Retrieve the JSON-config file from disk
    print(f"[{task.host.name}] ➤ Retrieving configuration JSON...")
    result = task.run(task=send_command, command="bash cat /etc/opt/srlinux/config.json")
    print(f"[{task.host.name}] ✓ Retrieved {len(result.result)} bytes of data")

    # 6) Save it locally
    filename = f"config_{task.host.name}_{ts}.json"
    print(f"[{task.host.name}] ➤ Saving configuration to {filename}...")
    with open(filename, "w") as fd:
        fd.write(result.result)
    print(f"[{task.host.name}] ✓ Configuration saved\n")

if __name__ == "__main__":
    print("▶ Running Nornir tasks...\n")
    nr.run(task=backup_config)
    print("▶ All tasks complete.")

Execute and install the plugins related to nornior

pip install nornir nornir-scrapli scrapli
python3 back-nornior.py

Output:

=== Nornir SR Linux Config Backup Script ===
Registering SimpleInventory plugin...
Plugin registered successfully.

Timestamp for this run: 20250717_151054

Initializing Nornir using inventory file:
  /home/netopschic/Documents/practicals/clab/clab-srlceos01/nornir-simple-inventory.yml

Nornir initialization complete.

▶ Running Nornir tasks...

[srl] ➤ Starting backup task
[srl] ➤ Disabling paging...
[srl] ✓ Paging disabled
[srl] ➤ Retrieving configuration JSON...
[srl] ✓ Retrieved 107479 bytes of data
[srl] ➤ Saving configuration to config_srl_20250717_151054.json...
[srl] ✓ Configuration saved

▶ All tasks complete.

The config file again will be saved in working directory.

Reference