This article provides information about  the various Junos configuration files - juniper.conf.gz, juniper.db, juniper.data, juniper.data+, juniper.conf+.gz, juniper.save, juniper.conf.1.gz, and rescue.conf.gz. 

What are the various Junos configuration files and where are they located on a router?

• juniper.conf.gz :
  
  It is the router configuring. It is used for rollback 0. Note that 'juniper.conf juniper.conf.gz' and 'juniper.conf.gz.jc' are morally equivalent. It is located in /config .

• juniper.db :
  
  This is the shared candidate database. It is located in /var/run/db .

• juniper.data :
  
  This is the committed configuration database (active configuration).It is located in /var/run/db .

• juniper.data+ :
  
  A copy of the candidate DB, which is used during commit check. During commit, it becomes juniper.data, if all goes well. It is located in /var/run/db .
• juniper.conf+.gz : This is the candidate configuration and exists only during commit. It is located in /config .

• junper.save :
  
  juniper.data may contain the results of expanding groups and applied transient changes from commit scripts. In either case, juniper.save represents the committed DB, prior to these changes being applied. This is needed for seeding private edit sessions, looking at the committed config without inheritance, and so on. It is located in /var/run/db .

• juniper.conf.1.gz to juniper.conf.3.gz :
  
  Rollback configurations 1 through 3. They are located in /config .

• juniper.conf.4.gz to juniper.conf.49.gz :
  
  Rollback configurations 4 through 49. Also, on J-series, at least the balance of configurations in /config and  /var/db/config are configurable. They are located in /var/db/config .

• rescue.conf.gz :
  
  A copy of a known good and working configuration, which can be loaded in case of emergency; without having to remember which rollback number to use. It is located in /config .