I don't mean file system snapshot, I mean the system state that is saved by the hibernate procedure (or deep sleep), to be recovered after a shutdown, so that I I'm able to restart from the situation (opened windows, running processes, etc) as it was when I did the save operation.
This is possible with Virtual Machines (yeah, I know it's physically different, cause they save the virtual hardware and don't rely on the OS capabilities) and basically, it should be the functionality run upon hibernation, without the final power off step.
I need this because my old Mac has started shutting down out of nothing, with the system restarting from scratch after that (so, all previous app have to be reopened, all unfinished jobs need to be restarted).
Note also I don't mean the "reopen apps" functionality that is available as a login option: that just relaunch apps, but they restart from scratch, not from their previous state.
SafeSleepfunction. These might be helpful links https://apple.stackexchange.com/questions/51725/do-macbooks-have-a-true-hibernate-option and https://superuser.com/questions/139354/how-can-i-manually-put-a-macbook-pro-to-hibernate-without-going-to-sleep-mode-fi/630985#630985. I can't say for sure there is or isn't a way to do this without also hibernate or sleeping the computer. – Unassuming Guy Apr 07 '18 at 00:02