You want to store a copy of a known good and working configuration that you can load in case of an emergency without having to remember which rollback number to use.
When a known stable and working configuration is loaded and running on the router, save it as the rescue configuration:
aviva@router1> request system configuration rescue save
You can also save it directly from configuration mode:
aviva@router1# run request system configuration rescue save
You create a rescue configuration to define a known working configuration or a configuration with a known state that you can roll back to at any time. This alleviates having to know the rollback number when you use the rollback command. You use the rescue configuration when you need to roll back to a known configuration or as a last resort if your router configuration and the backup configuration files become damaged beyond repair. The JUNOS software does not provide a default rescue configuration.
To return to the rescue configuration, load it with the following command:
 aviva@router1# rollback rescue  aviva@router1# commit commit complete
The JUNOS software stores the rescue configuration in the /config directory:
aviva@router1> file list /config /config: juniper.conf.1.gz juniper.conf.2.gz juniper.conf.3.gz juniper.conf.gz rescue.conf.gz
To save a different configuration as the rescue configuration, just use the request system configuration rescue save command to overwrite the existing file. If you discover that the existing rescue configuration is not correct, but you don't have something to replace it with, delete the rescue configuration so no one accidentally uses it:
aviva@router1> request system configuration rescue delete
Router Configuration and File Management
Basic Router Security and Access Control
Routing Policy and Firewall Filters