SRX340 upgrade process

There's a few different methods to upgrade and SRX security gateway cluster. You can go the traditional route, loading the new code on each cluster member node, staging the upgrade on both boxes, then synchronizing your reboot. You can also use a special "minimal downtime" method in which you isolate node members from each other, upgrading them out-of-band. And finally, for those chassis with dual routing-engines, you can perform an in-service upgrade. The method shown here is the traditional one and can be applied to any cluster comprised of two firewalls with a single RE each. In this example, I'm upgrading my SRX340 cluster at home from 18.something-or-other to 19.something-or-other. Update: Thanks to user High Pitch for pointing out that I forgot to include the link for copying files between cluster nodes. Here it is! https://forums.juniper.net/t5/SRX-Services-Gateway/Copy-and-login-from-node-0-to-node-1/m-p/103354#M12878