Re: interesting claims

From: fungal-net <fungalnet_at_obarun.org>
Date: Fri, 17 May 2019 11:21:00 +0000

Laurent Bercot:
> I'm not sure I understand your question, but I think there are
> really two different questions here; I'll try to reformulate them,
> correct me if I'm wrong.
>
> 1. Is booting a system a linear process where every step is
> reversible?

Well, assuming it wasn't from experience I was asking if it could
possibly be reversible. The answer did help me understand that what may
be theoretically possible it is most likely unnecessary, like having
very busy one-way streets around a building block and a parking space
became available 5 car lengths behind you. It may be quicker to go
around the block (big fat luck).

> 2. Is it possible to restart a system "from scratch" without
> rebooting?
>
> The answer to both questions is "not really, but it doesn't matter".
>
>. . . .
>. . . . .
>
> Stage 1 isn't reversible; once it's done, you never touch it again,
> you don't need to "reverse" it. It would be akin to also unloading
> the kernel from memory before shutting down - it's just not necessary.

But if you can unload it you can reload it or load a different one?

> . . . . .
> . . . .
>
> - If you want to kill every process but pid 1 and have the system
> reconstruct itself from there, then yes, it is possible, and that is
> the whole point of having a supervision tree rooted in pid 1. When
> you kill every process, the supervision tree respawns, so you always
> have a certain set of services running, and the system can always
> recover from whatever you throw at it. Try it: grab a machine with
> a supervision tree and a root shell, run "kill -9 -1", see what
> happens.

Very interesting:
Runit: I've never seen anything poweroff so fast (void faster than artix)
OpenRC: Nice,
  init
   |_ zsh
  when I exited the shell there was nothing but a dead cursor on my screen

S6/66: Goodmorning, it is like I had rebooted and was looking at my login:

sysV: init and 6 ttys with shell ... nothing can kill it that I know off.

sys.239.D: I hate to say, same behavior as s6/66

***BSD: I must research to find the equivalent to kill -9 -1 but it
seemed like openrc behavior.

>
> --
> Laurent
>
>
Received on Fri May 17 2019 - 11:21:00 UTC