Performing a Recovery Installation
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.
Starting in Junos OS Release 14.1, you can also use a system snapshot as a bootup option
when your Junos OS or configuration is damaged. The system snapshot feature takes a
“snapshot” of the files currently used to run the device—the complete contents of the
/config directories, which include the running Juniper Networks Junos OS, the active
configuration, and the rescue configuration, as well as the host OS—and copies all of
these files into an external USB flash drive. See Understanding System Snapshot.
NOTE: System snapshot is not supported on QFX10002 switches.
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” on page 139 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.
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 QFX Series device.
2. Reboot the QFX Series device.
NOTE: Do not power off the device if it is already on.
[edit system]
user@device> request system reboot
141Copyright © 2017, Juniper Networks, Inc.
Chapter 18: Restoring Junos OS
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