Creating an Emergency Boot Device for a QFX Series Device
If Junos OS on the QFX Series is damaged in some way that prevents the software from loading properly, you can use an emergency boot device to repartition the primary disk and load a fresh installation of Junos OS. Use the following procedure to create an emergency boot device.
Before you begin, you need to download the installation media image for your device and Junos OS release from https://www.juniper.net/customers/support/ .
 | Note: In the following procedure, we assume that you are creating the emergency boot device on a QFX3500 device. You can create the emergency boot device on another Juniper Networks switch or router, or any PC or laptop that supports Linux. The steps you take to create the emergency boot device vary, depending on the device. |
To create an emergency boot device from a QFX3500 device:
- Use FTP to copy the installation media image into the
/var/tmpdirectory on the QFX3500 device. - Insert a USB device into the USB port.
- From the Junos OS command-line interface (CLI), start
the shell:
user@device> start shell% - Switch to the root account using the su command:
% suPassword: passwordNote: The password is the root password for the QFX3500 device. If you logged in to the device as root, you do not need to perform this step.
- Enter the following command:
root@device% dd if=/var/tmp/filename of=/dev/da1 bs=16kThe device writes the installation media image to the USB device:
root@device% dd if=/var/tmp/install-media-qfx3500.junos_11.1 of=/dev/da1 bs=16k 11006+1 records in 11006+1 records out 180332544 bytes transferred in 71.764266 secs (2512846 bytes/sec)
- Log out of the shell:
root@device% exit% exituser@device>
