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Recovering the Installation Using an Emergency Boot Device

 

If Junos OS on your device is damaged in some way that prevents the software from loading correctly, you may need to perform a recovery installation using an emergency boot device (for example, a USB flash drive) to restore the default factory installation. Once you have recovered the software, you need to restore the device configuration. You can either create a new configuration as you did when the device was shipped from the factory, or if you saved the previous configuration, you can simply restore that file to the device.

If at all possible, you should try to perform the following steps before you perform the recovery installation:

  1. Ensure that you have an emergency boot device to use during the installation. See Creating an Emergency Boot Device for QFX Series Switches for information on how to create an emergency boot device.

  2. Copy the existing configuration in the file /config/juniper.conf.gz from the device to a remote system, such as a server, or to an emergency boot device. For extra safety, you can also copy the backup configurations (the files named /config/juniper.conf.n, where n is a number from 0 through 9) to a remote system or to an emergency boot device.

    You can use the system snapshot feature to complete this step. The system snapshot feature takes a “snapshot” of the files currently used to run the QFX Series switch—the complete contents of the /config and /var directories, which include the running Juniper Networks Junos OS, the active configuration, and the rescue configuration—and copies all of these files into a memory source. See Creating a Snapshot and Using It to Boot a QFX Series Switch.

    Note

    System snapshot is not supported on QFX10000 and QFX5200 switches.

    Caution

    The recovery installation process completely overwrites the entire contents of the internal flash storage.

  3. Copy any other stored files to a remote system as desired.

To reinstall Junos OS:

  1. Insert the emergency boot device into the device.

  2. Power cycle the device.

    The emergency boot device is detected. At this time, you can load the Junos OS from the emergency boot device onto the internal flash storage.

  3. The software prompts you with the following option if you have a snapshot saved on the emergency boot device:

    Select Install Junos Snapshot to install the snapshot.

    The software prompts you with the following option if you have Junos OS software from the factory installed on the emergency boot device.

    Select Install Juniper Linux Platform to install the Junos OS software from the emergency boot device.

  4. The device copies the software from the emergency boot device, occasionally displaying status messages. Copying the software can take up to 12 minutes.

    When the software is finished being copied from the emergency device to the device, the device reboots from the internal flash storage on which the software was just installed. When the reboot is complete, the device displays the Junos OS login prompt:

  5. Create a new configuration as you did when the device was shipped from the factory, or restore the previously saved configuration file to the device.

  6. Remove the emergency boot device.