Specifically, this question refers to the possibility of fixing a damaged system partition (causing "Cannot start the PS4" on boot) on a storage device (with many hours of game save data) by writing a cloned, healthy system partition from a new formatted storage device with a fresh install of the same level of firmware. This assumes however, that the PS4 hardware and the storage device are both healthy, and the only issue being a logically damaged partition.
On the psdevwiki, psdevwiki.com/ps4/Partitions the author(s) state that there are 15 partitions total. Only one of which is the User Data partition, which is the partition that needs to be untouched, in order to preserve that sensitive user data.
The theory is this:
The PS4 is initialized with a new, formatted storage device.
The same 15 partitions are created.
Using Clonezilla (or similar software), the healthy system partitions are cloned from that newly initialized, healthy storage device, to the storage device that is unable to boot.
The Playstation4 system accepts the healthy system partitions and allows the operating system to boot, and as such, the sensitive user data is able to be backed up.
There are limitations and considerations to this theory, however there is not much information available to be conclusive:
It is theorized that Playstation4 has hardware-level keyed encryption per storage device installed, which means there is a good chance cloning will not work due to differing keys between partitions. (the psdevwiki makes light of this in many categories, it appears that /system partitions are keyed with /user partitions)
The PS4 reacts to differing keys by reformatting the drive, erasing the User Data. (confirmed in many forum posts where users manually cloned partitions from one drive to the next)
This theory considers that the user has attempted to do any and all possible steps recommended by Sony. This includes all non-destructive options in Safe Mode.
What is my reason for asking this question to a ReverseEngineering community?
I simply want to know this: is there any possibility that user data on a healthy Playstation4 storage device can be recovered in the event of a logical system failure?
This is a major issue seen across many message boards on the internet. It extremely irresponsible of Sony to not have a viable way of recovering the system. Every other widely-used operating system in the world has a means of repairing itself, even from catastrophic corruption of system files.
I personally am a recent victim of Sony's unnecessary brute encryption measures. My personal saves were not affected, however, my partner's save data (of many thousands of hours) is now lost, even though they are intact inside the encrypted partition. This event has driven me to learn; in future I will have a dedicated USB storage device connected to the PS4 at all times, and backup user data on a scheduled interval.
However, I do not believe this loss (as insignificant as it is) is acceptable, which is why I am asking (for the sake of everyone who has gone through this) if it is even possible to restore the /user partition (by whatever means). Users deserve to have some possible recourse in the event of a logical system failure.