From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.comp.sysutils.supervision.general/2608 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: fungal-net Newsgroups: gmane.comp.sysutils.supervision.general Subject: Re: interesting claims Date: Fri, 17 May 2019 11:21:00 +0000 Organization: Obarun.Org Message-ID: <5f5b6035-240b-e6d6-497d-d9bb945d135f@obarun.org> References: <11997211556565598@myt6-27270b78ac4f.qloud-c.yandex.net> <20190501033355.6e41e707@mydesk.domain.cxm> <20190515132206.03f9736e@mydesk.domain.cxm> <20190516012214.15ffcf2e@dickeberta> <20190515210717.27b002ba@mydesk.domain.cxm> Reply-To: fungalnet@obarun.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="199344"; mail-complaints-to="usenet@blaine.gmane.org" To: supervision@list.skarnet.org Original-X-From: supervision-return-2198-gcsg-supervision=m.gmane.org@list.skarnet.org Fri May 17 13:22:25 2019 Return-path: Envelope-to: gcsg-supervision@m.gmane.org Original-Received: from alyss.skarnet.org ([95.142.172.232]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1hRawS-000pfR-GB for gcsg-supervision@m.gmane.org; Fri, 17 May 2019 13:22:24 +0200 Original-Received: (qmail 13636 invoked by uid 89); 17 May 2019 11:22:48 -0000 Mailing-List: contact supervision-help@list.skarnet.org; run by ezmlm Original-Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Original-Received: (qmail 13629 invoked from network); 17 May 2019 11:22:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=obarun.org; s=default; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version :Date:Message-ID:From:References:To:Subject:Reply-To:Sender:Cc:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=S4Ymxmorsiw3sBwuuhIkDR7Y7mhIsgK/eYU49uoFNd4=; b=jYWYyxhkCAz+db14gJT/HH8WwW +98ETzXu1MlGD4OUowemWXJET5qA55y/wdkiUdmo5GaQ4i+kC0UpGM+3LXWgnqQLUzr+h1rG1RYDN PgBZqbW+uJhaECnOPtGJQ7KHRH6A6vvJxKQGDuOnHdAtVknAN31WACRYHohECIhLUQK6t2OqH5wta FoSv13JXjjeRxOeedY3+PdDOSQ870y9LYTWVjihSp4jjNAM1RfX5vhyH2ELFkZRXfpgZNPGfRSkzj JK9gyv2FLIS9w1FLePLl+lLibRkkDa31XzDArJ+PFhOOib8+gDG1l24JM+o/veuAW7Ny11EJGdgzL KRkW/CLg==; In-Reply-To: Content-Language: en-US X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - sv75.ifastnet.com X-AntiAbuse: Original Domain - list.skarnet.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - obarun.org X-Get-Message-Sender-Via: sv75.ifastnet.com: authenticated_id: fungalnet@obarun.org X-Authenticated-Sender: sv75.ifastnet.com: fungalnet@obarun.org Xref: news.gmane.org gmane.comp.sysutils.supervision.general:2608 Archived-At: 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 > >