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Recovery Using an Emergency Boot Device

 

Emergency boot device helps your device to recover if the device’s Junos OS software is damaged.

Creating an Emergency Boot Device for Routers

If the device’s Junos OS software is damaged in some way that prevents Junos OS software from loading completely, you can use the emergency boot device to revive the device. The emergency boot device repartitions the primary disk and reloads a fresh installation of Junos OS software.

The procedures outlined in this section discuss how to create an emergency boot device for any ACX Series, M Series, MX Series, T Series, TX Matrix, and TX Matrix Plus router.

To create an emergency boot device:

  1. Use FTP to copy the installation media into the router’s /var/tmp directory.
  2. Insert the PC Card into the external PC Card slot or USB storage device into the USB port.
  3. In the UNIX shell, navigate to the /var/tmp directory:
  4. Log in as su:
  5. For Junos OS with upgraded FreeBSD only, expand the image, for example:

    where installMedia refers to the installation media ed into the /var/tmp directory. For example, for Junos OS with upgraded FreeBSD, the filename might be junos-install-media-usb-mx-x86-64-16.1R2.11.img.gz. (To determine which platforms use Junos OS with upgraded FreeBSD, see Release Information for Junos OS with Upgraded FreeBSD.)

  6. Issue the following commands:
    • For Junos OS with upgraded FreeBSD:

    • For Junos OS:

    where:

  7. Log out as su:

Creating an Emergency Boot Device for QFX Series Switches

If Junos OS on the device 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 the installation media image for your device and Junos OS release from https://www.juniper.net/customers/support/ .

Note

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:

  1. Use FTP to copy the installation media image into the /var/tmp directory on the device.
  2. Use gunzip to unzip the image file.
  3. Insert a USB device into the USB port.
  4. From the Junos OS command-line interface (CLI), start the shell:
    user@device> start shell
    %
  5. Switch to the root account using the su command:
    % su
    Password: password
    Note

    The password is the root password for the device. If you logged in to the device as root, you do not need to perform this step.

  6. Enter the following command on the device:
    root@device% dd if=/var/tmp/filename of=/dev/da1 bs=1m


    The device writes the installation media image to the USB device:

  7. Log out of the shell:
    root@device% exit
    % exit
    user@device>

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.

    Warning

    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.

Performing a Recovery Installation

If the device’s software is corrupted or otherwise damaged, you may need to perform a recovery installation, using the emergency boot device to restore the default factory installation. Once you have recovered the software, you will need to restore the router or switch’s configuration. You can either create a new configuration as you did when the device was shipped from the factory, or if you saved the device’s previous configuration, you can simply restore that file to the system.

Depending on the situation, you should try to perform the following steps before you perform the recovery installation:

  1. Ensure you have an emergency recovery disk to use during the installation. When the router or switch is first shipped, an emergency recovery disk is provided with it. For instructions on creating an emergency boot device, see Creating an Emergency Boot Device for Routers

  2. Copy the existing configuration in the file /config/juniper.conf.gz from the device to a remote system. 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).

    Warning

    The recovery installation process completely overwrites the entire contents of the fixed storage media.

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

To reinstall Junos OS:

  1. Insert the removable media emergency boot device into the device.

    Note

    You can store a configuration on installation media such as a PC Card or USB stick.

  2. Reboot the device.

    If the CLI is still active, issue the request system reboot command from command mode to reboot the device.

    If the CLI is not working, manually power off the device using the main power switch, wait 10 seconds, and then power the device back on.

  3. When the software prompts you with the following question, type y:

    Note

    Introduced in Junos OS Release 15.1, Junos OS with upgraded FreeBSD does not display the following warning. To determine which platforms use Junos OS with upgraded FreeBSD, see Release Information for Junos OS with Upgraded FreeBSD.

    The device copies the software from the removable media emergency boot device onto your system, occasionally displaying status messages. Copying the software can take up to 45 minutes, depending on the device. When the process is complete, the router boots into Amnesiac state and the login prompt is displayed.

  4. Remove the removable media emergency boot device.

  5. Log in as root on the device’s console port and issue the request system reboot command from command mode to reboot the device.

    The device reboots from the boot device on which the software was just installed. When the reboot is complete, the device displays the login prompt.

  6. Create a new configuration as you did when the device was shipped from the factory, or restore a previously saved configuration file to the system. For more information, see Creating a New Configuration on a Single Routing Engine, Creating a New Configuration with Redundant Routing Engines, and Restoring a Saved Configuration.