add-config-param

Adding a Configuration Parameter to NetBox

NetBox has two distinct kinds of configuration parameters. Choose the right one before writing any code:

Use dynamic when:

• Operators need to tune the value without a service restart
• The parameter controls UI behavior or defaults (banners, page sizes, default values)
• Examples: PAGINATE_COUNT, MAINTENANCE_MODE, BANNER_TOP

Use static when:

• The value must not change at runtime (auth backends, database config, secret keys)
• The value controls infrastructure that requires a restart anyway
• Examples: ALLOWED_HOSTS, REMOTE_AUTH_BACKEND, LOGGING

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Adding a Dynamic Configuration Parameter

Dynamic parameters are defined in netbox/netbox/config/parameters.py, stored in the ConfigRevision.data JSONField, cached in Redis, and editable via Admin > System > Configuration History.

Step 1 — Add to PARAMS

File: netbox/netbox/config/parameters.py

Add a ConfigParam entry to the PARAMS tuple, grouped logically with related parameters:

ConfigParam(
    name='MY_PARAM',
    label=_('My param'),
    default=<default_value>,
    description=_("One-sentence description of what this controls"),
    field=forms.BooleanField,   # or IntegerField, CharField, JSONField, SimpleArrayField
    # field_kwargs only when extra widget/validation config is needed:
    field_kwargs={
        'widget': forms.Textarea(attrs={'class': 'vLargeTextField'}),
    },
),

Common field choices:

The default value is returned whenever no ConfigRevision row exists and the parameter is not hard-coded in configuration.py.

Step 2 — Use the parameter in code

Access via get_config() (request-scoped, cached) or the ConfigItem callable (deferred):

from netbox.config import get_config

# One-time read:
value = get_config().MY_PARAM

# Deferred (evaluated later):
from netbox.config import ConfigItem
MY_PARAM = ConfigItem('MY_PARAM')

get_config() returns the Config object which tries:

1. Hard-coded value in Django settings (set by configuration.py)
2. Redis-cached active ConfigRevision
3. ConfigParam.default

Step 3 — Document in the configuration docs

Add a section to the appropriate file under docs/configuration/:

Template for a dynamic parameter doc section:

## MY_PARAM

!!! tip "Dynamic Configuration Parameter"

Default: `<default_value>`

One or two sentences describing what the parameter does, what values are accepted,
and any side effects.

Step 4 — Register in the dynamic params index

File: docs/configuration/index.md

Add the new parameter to the bulleted list under "Dynamic Configuration Parameters", keeping the list alphabetically ordered:

* [`MY_PARAM`](./miscellaneous.md#my_param)

Step 5 — Optionally add to the example config

If the parameter is important enough that operators should know they can hard-code it, add a commented entry to netbox/netbox/configuration_example.py:

# MY_PARAM = <default_value>

Place it near related parameters.

No migration needed

Dynamic parameters are stored in the ConfigRevision.data JSONField, which already exists. No database migration is required when adding a new ConfigParam.

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Adding a Static Configuration Parameter

Static parameters live in settings.py and are read at startup from configuration.py. They take effect only after the WSGI service is restarted.

Step 1 — Add to settings.py

File: netbox/netbox/settings.py

Add a line in the "Set static config parameters" block, alphabetically within its logical group:

MY_PARAM = getattr(configuration, 'MY_PARAM', <default_value>)

For required parameters (no default), use getattr(configuration, 'MY_PARAM') with no fallback and add the parameter name to the required check near the top:

for parameter in ('ALLOWED_HOSTS', 'MY_PARAM', 'SECRET_KEY', 'REDIS'):
    if not hasattr(configuration, parameter):
        raise ImproperlyConfigured(f"Required parameter {parameter} is missing from configuration.")

Step 2 — Add validation (if needed)

If the parameter has constrained values, add an ImproperlyConfigured check immediately after the getattr line:

MY_PARAM = getattr(configuration, 'MY_PARAM', 'option_a')
if MY_PARAM not in ('option_a', 'option_b'):
    raise ImproperlyConfigured(f"MY_PARAM must be 'option_a' or 'option_b' (found {MY_PARAM})")

For complex validation (importable paths, valid URLs, etc.) follow the patterns of PROXY_ROUTERS or RELEASE_CHECK_URL in settings.py.

Step 3 — Add to the example config

File: netbox/netbox/configuration_example.py

Add a commented entry with a brief inline comment explaining the parameter:

# MY_PARAM = 'default_value'    # Short description of what this does

Step 4 — Document

Add a section to the appropriate docs/configuration/*.md file:

## MY_PARAM

Default: `<default_value>`

One or two sentences describing the parameter, accepted values, and any constraints.

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Static parameters do not get the !!! tip "Dynamic Configuration Parameter" admonition.

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Common Gotchas

• Dynamic params don't need a migration — the value is stored in the ConfigRevision.data JSONField which already exists.
• Hard-coding a dynamic param in configuration.py overrides the UI — the loop at the bottom of settings.py (for param in CONFIG_PARAMS: ...) sets the Django setting, which Config.__getattr__ checks first. Document this behaviour in the parameter's doc page.
• forms.BooleanField with required=False: the ConfigFormMetaclass always adds required=False, so a BooleanField correctly represents a three-state (True / False / unset-use-default) UI. No extra field_kwargs needed for booleans.
• SimpleArrayField needs base_field: always pass field_kwargs={'base_field': forms.CharField()}.
• No ruff format on existing files — use ruff check only.

References

• Dynamic param definitions: netbox/netbox/config/parameters.py
• Config loading / Config class: netbox/netbox/config/__init__.py
• ConfigRevision model: netbox/core/models/config.py
• ConfigRevisionForm (metaclass): netbox/core/forms/model_forms.py
• Static config loading: netbox/netbox/settings.py lines 67–213
• Example config: netbox/netbox/configuration_example.py
• Config tests: netbox/netbox/tests/test_config.py
• Documentation: docs/configuration/