[SRX] Recovering a device stuck at "Can't load Kernel" or in boot loop state

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Summary:

This article discusses how to restore a device if the Junos image on CF is corrupted, and you are seeing the error message Can't Load Kernel or the device keeps going into a continuous boot loop. To recover the faulty device, take a snapshot of a healthy device; this creates a fresh Junos image to be loaded on the faulty device.

Symptoms:

While upgrading the following error is seen:

###Entering boot mastership relinquish phase
KDB: enter: panic

This either leads into a boot loop or else the error message Can't Load Kernel is seen. The snapshot method can be tried to recover the faulty device.

Cause:
 
Solution:
  1. Plug a USB drive into a known healthy SRX which is of the same model and configuration as the faulty device. Run the following command:

  2. >request system snapshot media usb

  3. When the snapshot is complete, power down the faulty SRX. Remove the USB from the healthy SRX and plug it into the faulty SRX.

  4. Power on the faulty device on and see if it will boot from the USB drive.

  5. If it does, then snapshot the image from the USB drive back onto the compact flash (CF) with the following command:

  6. >request system snapshot media internal

    This will load the image from the USB onto the SRX's internal compact flash.

  7. Then reboot the device from the compact flash. Use the following command:

  8. >request system reboot media internal

Note: Taking a snapshot of the healthy device will also take a snapshot of the configuration, and will load the same configuration on the faulty device.

If you need to install the Junos image from the loader prompt please refer to the following document: Installing Junos OS on SRX Series Devices From the Boot Loader Using an USB Storage Device

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