Creating an Emergency Boot Disk

If the router’s Junos OS is damaged in some way that prevents the Junos OS from loading completely, you can use the emergency boot disk to revive the router. The emergency boot disk repartitions the primary disk and reloads a fresh installation of the Junos OS.

The procedures outlined in this section discuss how to create an emergency boot disk for any M Series, MX Series, T Series, TX Matrix, or TX Matrix Plus router.

To create an emergency boot disk:

1. Use FTP to copy the installation media into the router’s /var/tmp directory.
2. Insert the PC Card into the external PC Card slot.
3. In the UNIX shell, navigate to the /var/tmp directory:

   start shell
   cd /var/tmp

4. Log in as su:

   su [enter]
   password: [enter SU password]

5. issue the following commands:

   dd if=/dev/zero of=/dev/externalDrive count=20
   dd if=installMedia of=/dev/externalDrive bs=64k

   where:

   • externalDrive—Refers to the removable media name. For example, the removable media name on the M120 is da0 for both Routing Engines. For the names of the storage media, see Routing Engines and Storage Media Names (M Series, MX Series, T Series, TX Matrix, and TX Matrix Plus Routers).
   • installMedia—Refers to the installation media downloaded into the /var/tmp directory. For example, install-media-9.0R2.10–domestic.tgz.

   The following code example can be used to create an emergency boot disk using a PC Card on an M20 router:

   dd if=/dev/zero of=/dev/ad3 count=20
   dd if=install-media-9.0R2.10–domestic.tgz of=/dev/ad3 bs=64k

   The following code example can be used to create an emergency boot disk using a USB storage device on an M120 router or a TX Matrix Plus router:

   dd if=/dev/zero of=/dev/da0 count=20
   dd if=install-media-9.0R2.10–domestic.tgz of=/dev/da0 bs=64k

6. Log out as su:

   exit