The Junos PyEZ Config utility is the primary tool for managing device configurations. By default, it operates in private edit mode. When a configuration session is initiated, PyEZ creates a private copy of the candidate configuration. This allows an automation script to load, modify, and commit changes without interfering with other users or automation processes that might be simultaneously editing the shared candidate configuration. This behavior provides a safe and isolated environment for programmatic configuration changes, preventing potential conflicts.

A. shared: This is the default configuration mode for interactive CLI users, not for PyEZ. Using this mode in automation could lead to conflicts with other users.

B. dynamic: The dynamic database is used for transient configuration information, such as that provided by DHCP, and is not the default target for user-initiated configuration changes.

D. ephemeral: The ephemeral database is a powerful feature for automation but is not the default. It must be explicitly specified to be used by PyEZ for configuration updates.

1. Juniper Networks TechLibrary, Junos PyEZ APIs, jnpr.junos.utils.config Module.

Reference: In the documentation for the Config class constructor (init), the mode parameter is described as: "The configuration mode. The supported modes are 'private', 'exclusive', 'batch', and 'dynamic'. The default is 'private'."

Link: https://www.juniper.net/documentation/us/en/software/junos-pyez/junos-pyez-developer/junos-pyez/topics/ref/api/jnpr.junos.utils.config.html

2. Juniper Networks TechLibrary, Using the Junos PyEZ Configuration Utility.

Reference: Under the section "Lock the Configuration," the documentation states: "By default, the Config utility uses private edit mode when it locks the configuration." This explicitly confirms the default behavior.

Link: https://www.juniper.net/documentation/us/en/software/junos-pyez/junos-pyez-developer/junos-pyez/topics/task/junos-pyez-configuration-utility-using.html