Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Troubleshooting a Switch That Has Booted from the Backup Junos OS Image



Description: The switch boots from the backup root file partition. It is possible that the primary copy of Junos OS failed to boot properly, which could indicate that it is corrupted. This event is flagged in two ways:

  • Upon login through the console or management port, the following warning message is displayed:

  • The following alarm message is generated:

    user@switch> show chassis alarms

    If the switch is in a Virtual Chassis, the switch member number appears in the Description field, where the switch is called a host.


Install a new Junos OS image on the partition that had the corruption, or take a snapshot (use request system snapshot) of the currently active partition and use it to replace the image in the alternate partition:

If the switch is a standalone switch or a Virtual Chassis master switch, enter this command:

user@switch> request system snapshot slice alternate

If the switch is a Virtual Chassis member switch (not the master), enter this command on the Virtual Chassis:

user@switch> request system snapshot slice alternate member member-id

where member-id is the Virtual Chassis member ID number.