What is the purpose of the rollback command in Junos?

The rollback command in Junos is designed to discard changes made to the candidate configuration. When you make configuration changes in Junos, those changes are initially applied to a candidate configuration, which is a temporary working copy of the configuration that is not yet active.

When the rollback command is executed, it effectively reverts the candidate configuration to a previous state, which allows the administrator to discard any uncommitted changes and restore the configuration to a known good state. This is particularly useful when a series of modifications have been made but are no longer desired or if they have introduced issues.

In contrast, the other options do not accurately describe the functionality of the rollback command. While it does not apply configuration changes immediately (as that would be the commit command), it also does not create a backup of the current configuration, as Junos provides different methods for backing up configurations. Additionally, the rollback command is not used to discard changes in the active configuration, since changes made to the active configuration are only affected once they are committed.