Reply to post: Re: Honest inquiry

systemd-free Devuan Linux hits version 1.0.0

Peter Gathercole Silver badge

Re: Honest inquiry

Um. Monitoring processes is exactly what SysVinit does, but it requires you to actually have processes directly created by init that stick around.

Look at the entries in /etc/inittab. See field 3 in each line, the one that says wait, once or respawn. Respawn allows you to have a service that will be re-stared if the process dies.

What you are referring to as SysVinit is actually the /etc/rc script that is called from init on runlevel change, that runs the scripts from /etc/rc.d (although different SysV UNIX ports actually implement it slightly differently). While this is part of the init suite, it is not init itself.

The concept of init in UNIX goes back to before SysV. I have a copy of the Lyons Edition 6 commentary, and that references an init process, although I think that the /etc/inittab file did not exist at that time. I will fire up my Nordier Intel port of Edition 7 VM at some point to refresh my memory about how Edition 7 started the initial processes.

The rc.d directory heirarchy of scripts appeared at some point between SVR2 and SVR3 IIRC. The first UNIX I remember seeing it in was R&D UNIX 5.2.6 (which was an internal AT&T release).

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