Creating an Emergency Boot Disk


You want to create a boot disk to use in an emergency if the software and filesystems on the router become so damaged that you just want to reconfigure the router from scratch.


Create a PCMCIA boot flash card that contains the JUNOS install media. First, copy the install media from the JUNOS software download page on the Juniper Networks support site ( On M-series and T-series routers, copy this file to the router's /var/tmp directory. Then, insert a PC card into the router's drive and copy the install media to the PC card:

	aviva@router1> start shell
	aviva@router1% cd /var/tmp
	aviva@router1% su
dd if=/dev/zero of=/dev/rad3 count=20
	root@router1% dd if=install-media-7.4R1.7-domestic of=/dev/rad3 bs=64k

To create a boot flash card for a J-series router, copy the install media to a Windows or Unix PC and uncompress it with gzip or WinZip. Connect a PCMCIA adapter or USB card reader to the PC and insert a compact flash card into the device. On a Unix PC, use the following commands to copy the image to the compact flash:

	root@RouterJ# dd if=junos-jseries-7.4R1.7-export-cf256. of=/dev/hde
	250368+0 records in
	250368+0 records out

On a Windows XP or Windows 2000 PC, use either the Norton Ghost utility or the dd command shown previously.


One of the tasks you can do to prepare for router disaster recovery is to create an emergency PCMCIA boot media. This is a bootable media that contains an image of a specific JUNOS software release. When you boot the router from this media, it installs the complete router from scratch, first doing a full reformat of the hard disk and flash, then completing a full new install of all the JUNOS software.

Use the PCMCIA boot media in disaster recovery when a router is hosed and you need to execute a complete reinstall from scratch. To boot from this media, the PCMCIA must first be inserted into the slot on the Routing Engine. When the router boots, the first thing it looks for is a PCMCIA in the slot. If it's not there, it moves on to the flash drive. If the PCMCIA is there, the router stops and waits for a user with console access to the router to press Enter to continue. The router does not automatically execute the reformat and reinstallation; you must tell it to do so. That way, if someone inserts the PCMCIA in the slot by mistake, the router doesn't format and reinstall when you didn't plan for it to do so.

The J-series router follows the same procedure but uses a compact flash card instead of a PCMCIA card. This recipe shows the commands to use for a 256-MB compact flash.J-series install media are also available for other sizes, including 128, 512, and 1,024 MB.

See Also

Juniper Networks web site (

Router Configuration and File Management

Basic Router Security and Access Control





Router Interfaces

IP Routing

Routing Policy and Firewall Filters







IP Multicast

JUNOS Cookbook
Junos Cookbook (Cookbooks (OReilly))
ISBN: 0596100140
EAN: 2147483647
Year: 2007
Pages: 290
Authors: Aviva Garrett © 2008-2020.
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