Routing Engine Boot Devices

Generally the router boots on the primary boot device, which is the flash disk. This device contains the current router configuration and the last three committed configurations in the juniper.conf, juniper.conf.1.gz, juniper.conf.2.gz, and juniper.conf.3.gz files, respectively. These files are located in the /config directory.

If the flash disk fails, the router attempts to boot from the hard disk, which is the alternate boot device.

If a removable media is installed when the router boots, the router attempts to boot the image on it. If the booting fails, the router tries the flash drive and then the hard disk.

If the router boots from an alternate boot device, the JUNOS software displays a message indicating this when you log in to the router. For example, this message shows that the software booted from the hard disk (/dev/ad2s1a):

login: username

Password: password 

Last login: date on terminal

--- JUNOS 6.4 R1 built date

---

--- NOTICE: System is running on alternate media device (/dev/ad1).