we have some old juniper ex4200 in our stock and it shows following warning in console :

--- JUNOS 12.3R3.4 built 2013-06-14 00:08:02 UTC

** **
** **
** 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 and if auto-snapshot feature is not **
** enabled. **
** **

maybe our old technical team set to boot from backup, so is it safe to use this? because we do not have access to old staffs.

also we tried https://kb.juniper.net/InfoCenter/index?page=content&id=KB23180 and copy snapshot from backup to primary but after reboot it boots again from backup. and there is no error when juniper wants boot up.


  • Please paste results of "sh sys stor part" Nov 25, 2019 at 17:16
  • I've had equipment do that, too. It's fairly easy to repair. (as long as the internal flash isn't damaged)
    – Ricky
    Nov 25, 2019 at 17:38
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Dec 16, 2020 at 23:47

1 Answer 1


You may have missed the most important part of the proceedure:

To go back to the Primary partition, you can use the request system reboot slice alternate media internal command. If you do not use this command, the switch will then boot from the backup partition on successive reboots; which is the current Active partition.

After request system snapshot ... completes, you have to tell it to reboot into the primary partition.

If that doesn't work, you may need to completely reinstall the system. (boot from usb / network, wipe the internal flash, install junos to both partitions.)

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