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Boot from USB and Recovering from a Failed Software Upgrade



Article ID: KB10386 KB Last Updated: 27 Feb 2020Version: 10.0

Junos devices have the capability of booting from a USB Sandisk formatted memory device for software recovery, software upgrades, or for formatting the disk of the Junos device.


Junos device environments for booting from USB:

  • If the Junos software loads but the CLI is not working for any reason.

  • If the switch has no software installed, you can use a recovery installation procedure to install the Junos software. 

  • Format the disk prior to software installation.
Booting from USB Sandisk or recovering from a Failed Software Upgrade on a Junos device.

If the Junos software loads but the CLI is not working for any reason, or if the switch has no software installed, you can use this recovery installation procedure to install the Junos software.

If there is already a Junos image on the system, you can either install the new Junos package in a separate partition and both Junos images will remain on the system, or you can wipe the disk clean before the new installation proceeds.

To perform a recovery installation:
  1. Power on the switch. The loader script starts.

  2. After the Loading /boot/defaults/loader.conf displays, you are prompted with:
    Hit [Enter] to boot immediately, or space bar for command prompt.
  3. Hit the space bar to enter the manual loader. The loader> prompt displays. 
    (NOTE: There is a 1 second delay for hitting the space bar)

  4. Enter the following command:
    install source

    • source: Represents the name and location of the Junos software package either on a server on the network or as a file on an external USB drive:
      • Network address of the server and the path on the server.

      • The Junos package on a USB device is commonly stored in the root drive as the only file.

  5. The installation proceeds as normal and ends with a login prompt.

For additional information, refer to Booting an EX Series Switch Using a Software Package Stored on a USB Flash Drive.
Modification History:

2020-02-27: Added related links to KB12880 and KB20643
2020-02-03: Added related link to tech doc on Recovery Using an Emergency Boot Device.

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