This Device has Booted from the Backup JunOS Image EX and SRX

Recently I encounter weird issue with JunOS. While Cold Booting the Juniper ex4200 switch its shows following message.

I do nothing just first boot the device thus face unknown reason message. Then I dig the google however some command doesn't work except below one. This JunOS version was 12.3.

sw1@jpudasaini>show system storage partition

Solution
EX
root>request system reboot slice alternate media internal 

SRX
root>request system reboot media internal 

Now reboot your device and the error message is already gone. To verify the which boot partition do used by your device use the following command.