Software Installation Overview

The JUNOS Internet software is preinstalled on the router. Once the router is powered on, it is ready to be configured. The primary copy of the software is installed on a nonrotating flash disk. Two backup copies are included, one on the router's rotating hard disk and a second on the removable media (either an LS-120 floppy disk [a 120-MB disk] or a PC Card) that is shipped with the router.

When the router boots, it first attempts to start the software image from the removable media if one is installed in the router. If this fails, the router next tries the flash disk, then finally the hard disk. Normally, you want the router to boot from the flash disk.

To upgrade the software, you copy a set of software images over the network to the router's flash disk using SCP or another similar utility. The JUNOS software set consists of three images, one for the software processes, a second for the kernel, and the third for the Packet Forwarding Engine. You normally upgrade all images simultaneously.