From KB11194 http://kb.juniper.net/InfoCenter/index?page=content&id=KB11194
JUNOS Command Line interface allows the user to export the configuration file into an FTP server and to import it back to the switch. The information below describes the steps to backup and restore JUNOS configuration file on FTP server.
Backup configuration file on FTP.
The following configuration sample shows how to backup the JUNOS configuration file on FTP server.
On every commit applied on CLI, the EX switch will transfer a copy of the configuration file to an ASCII file on FTP server. The filename created on the FTP server contains hostname, date and time signature.