This happens when the main image is corrupt or has failed a boot.  When this happens you may or may not have a functional switch.

Did I mention I love this message!!!

** **
** **
** 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. **
** **

What should happen is that you have a backup image which is the same as your primary image and you boot up and everything is OK.

Sometimes I have run into the instance where the configuration partition is corrupt and you cannot write to it because it booted as a read only.  The switch may still function correctly if it is a member of a virtual chassis however you cannot commit any new changes.

You have to take the switch down for maintenance and correct the primary image.

Some times the method of just copying the alternate image to primary with the command request system snapshot slice alternate does not copy because of the corruption.

You can try and download a new image form a tftp, ftp or web sever using request system software add url:\\server/path

There is time when this will not work because either the networking or virtual chassis is not up on the individual switch so there is no network access, you can try using a USB stick.

If all else fails you can do the following, boot into the loader and then tftp a new image


1- Reboot the Switch

2- Interrupt the boot at the loader prompt

Hit [Enter] to boot immediately, or space bar for command prompt.

3- You will now be at the boot loader prompt


4- Set the following info up at the loader prompt

set ipaddr=x.x.x.x

set netmask=x.x.x.x

set serverip=x.x.x.x

Where ipaddr is the switch temporary IP address, netmask is the netmask for the switch, serverip is the tftp server address, note the tftp server should be on the same L2 lan segment.

5- Then issue the install command with a path and image, you can add the option  –format  for example

install –format tftp://

At this point the switch is factory default reload your config or add it back to your virtual chassis and your back up and running.  By using the format option you add the image to both the primary and secondary image slices.

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