Backup:
Use start shell command then:
root@% tftp 100.1.1.50
tftp> put juniper.conf.1.gz
Sent 1221 bytes in 0.0 seconds
tftp> quit
root@%
Restore:
From console with root, run
tftp> get juniper.conf.1.gz
Sent 1221 bytes in 0.0 seconds
tftp> quit
root@% cli
root>edit
root# config override juniper.conf.1.gz
root# commit