Recovering System Booted From Backup JUNOS Image

The following alarm message is generated:

user@switch> show chassis alarms
1 alarms currently active
Alarm time Class Description
2011-02-17 05:48:49 PST Minor Host 0 Boot from backup root

***********************************************************************
**                                                                   **
**  WARNING: THIS DEVICE HAS BOOTED FROM THE BACKUP JUNOS IMAGE      **
**                                                                   **
**  It is possible that the primary copy of JUNOS failed to boot up  **
**  properly, and so this device has booted from the backup copy.    **
**                                                                   **
**  Please re-install JUNOS to recover the primary copy in case      **
**  it has been corrupted.                                           **
**                                                                   **
***********************************************************************

To verify if the primary partition is rebuilt, run one of the following show commands. The same commands also inform about which partition is the current active partition.

show system storage partitions

Sample output:

root> show system storage partitions 
fpc0:
--------------------------------------------------------------------------
Boot Media: internal (da0)
Active Partition: da0s1a
Backup Partition: da0s2a <-- this is the backup slice 
Currently booted from: backup (da0s2a) <-- shows booted from that slice
Partitions information:
Partition Size Mountpoint
s1a 184M altroot 
s2a 184M / 
s3d 369M /var/tmp 
s3e 123M /var 
s4d 62M /config 
s4e unused (backup config)

Copy the Junos image from the backup partition to the primary partition, by using the following snapshot command:

For EX Switches:

request system snapshot media internal slice alternate

For SRX Routers:

request system snapshot slice alternate

You will see the following message as the media is copied over:

Formatting alternate root (/dev/da0s2a)...
Copying '/dev/da0s1a' to '/dev/da0s2a' .. (this may take a few minutes)
The following filesystems were archived: /

_{Note: This step ensures that you have consistent images on both the primary and backup partitions. This operation can take 5 to 10 minutes to complete.}

The above command ensures that the alternate partition is repaired, without requiring a reboot. You can verify both the partitions by using the following command:

show system snapshot media internal

This will show the time/date stamp for both partitions, which should show the current date/time on the (primary) partition which has been restored.  See sample output below:

For EX Switches:

root@ex> show system snapshot media internal
fpc0:
--------------------------------------------------------------------------
Information for snapshot on       internal (/dev/da0s1a) (backup)
Creation date: Dec 17 16:58:29 2015 <-- Displays current date/time of operation in step 3.1
JUNOS version on snapshot:
  jbase  : ex-12.3R11.2
  jkernel-ex-2200: 12.3R11.2
  jcrypto-ex: 12.3R11.2
  jdocs-ex: 12.3R11.2
  jswitch-ex: 12.3R11.2
  jpfe-ex22x: 12.3R11.2
  jroute-ex: 12.3R11.2
  jweb-ex: 12.3R11.2
  fips-mode-arm: 12.3R11.2
Information for snapshot on       internal (/dev/da0s2a) (primary)
Creation date: Dec 16 17:13:15 2015
JUNOS version on snapshot:
  jbase  : ex-12.3R11.2
  jkernel-ex-2200: 12.3R11.2
  jcrypto-ex: 12.3R11.2
  jdocs-ex: 12.3R11.2
  jswitch-ex: 12.3R11.2
  jpfe-ex22x: 12.3R11.2
  jroute-ex: 12.3R11.2
  jweb-ex: 12.3R11.2
  fips-mode-arm: 12.3R11.2

For SRX Routers:

root@srx> show system snapshot media internal
Information for snapshot on       internal (/dev/da0s1a) (primary)
Creation date: Jan 22 23:48:47 2016 <-- Displays current date/time of operation in step 3.1
JUNOS version on snapshot:
  junos  : 12.1X44-D15.5-domestic
Information for snapshot on       internal (/dev/da0s2a) (backup)
Creation date: Jan 1 06:08:27 2000
JUNOS version on snapshot:
  junos  : 12.1X44-D15.5-domestic

If there is no risk to the network or customer, the system can be rebooted immediately. To get rid of the above alarm, use the following command to ensure that the switch boots from the primary partition:

For EX Switches:

request system reboot slice alternate media internal

For SRX Routers:

request system reboot

The system, after the above command is executed, will reboot from the primary partition. The alarm or the warning message will no longer be displayed.

If the system needs to be rebooted after-hours, contact the customer and schedule the maintenance window. You may use the following command to schedule the reboot after X amount of minutes:

For EX Switches:

request system reboot slice alternate media internal in 480

For SRX Routers:

request system reboot in 480

Change the value after "in" to be the amount of minutes to reach the maintenance window scheduled with the customer.  In this scenario, the system would reboot in 8 hours from the time the command is issued (60 minutes x 8 hours = 480)