Installing Junos OS on SRX Series Devices from the Boot Loader Using a USB Storage Device


To install Junos OS Release 10.0 or later from the boot loader using a USB storage device:

  1. Format a USB storage device in MS-DOS format.
  2. Copy the Junos OS image onto the USB storage device.
  3. Plug the USB storage device into the SRX Series device.
  4. Stop the device at the loader prompt and issue the following command:

    An example of a command is as follows:

    This formats the internal media and installs the new Junos OS image on the media with dual-root partitioning.

  5. Once the system boots up with Junos OS Release 10.0 or later, upgrade the U-boot and boot loader immediately. See Upgrading the Boot Loader on SRX Series Devices for more information.
  6. Remove the USB flash drive.

On SRX300, SRX320, SRX340, SRX345, and SRX550M devices, frequent plug and play of USB keys is not supported. You must wait for the device node creation before removing the USB key.


If an installation error occurs, the LEDs turn red, which might indicate that the Junos OS image on the USB flash drive is corrupted. An installation error can also occur if the current configuration on the SRX Series device is not compatible with the new Junos OS version on the USB or if there is not enough space on the SRX Series device to install the image. You must have console access to the SRX Series device to troubleshoot an installation error.