How the Configuration Is Stored

hen you edit a configuration, you work in a copy of the current configuration to create a candidate configuration. The changes you make to the candidate configuration are visible in the CLI immediately, so if multiple users are editing the configuration at the same time, all users can see all changes.

To have a candidate configuration take effect, you commit the changes. At this point, the candidate file is checked for proper syntax, activated, and marked as the current, operational software configuration file. If multiple users are editing the configuration, when you commit the candidate configuration, all changes made by all the users take effect.

In addition to saving the current configuration, the CLI saves the current operational version and the previous nine versions of committed configurations. The most recently committed configuration is version 0 (the current operational version, which is the default configuration that the system returns to if you roll back to a previous configuration), and the oldest saved configuration is version 9. The currently operational JUNOS software configuration is stored in the file juniper.conf, and the last three committed configurations are stored in the files juniper.conf.1, juniper.conf.2, and juniper.conf.3. These four files are located in the directory /config, which is on the router's flash drive. The remaining six previous versions of committed configurations, the files juniper.conf.4 through juniper.conf.9, are stored in the directory /var/db/config on the hard disk.

PIC 2 illustrates the various router configuration states and the configuration mode commands you use to load, commit, copy, save, or roll back the configuration.

PIC 2 : Commands for Storing and Modifying the Router Configuration

pic2