On Fri, Dec 28, 2012 at 12:53 PM, Kevin Chadwick <ma1l1i...@yahoo.co.uk> wrote: > On Thu, 27 Dec 2012 17:38:15 -0600 > Canek Peláez Valdés <can...@gmail.com> wrote: > >> In SysV, I can *write* the daemon in the init script. >> In *that* sense, the init system tells the daemon how to do things, > > Please explain, sure there is the environment that tells a daemon what > to do. No shell can tell a c daemon like sshd how to drop priviledges > or use systrace but it could do these things for it in a more fine > grained manner before it tries and fails itself or if the daemon > wishes it to like monit. It's still not telling how but duplicating or > removing the need. That's just a bonus that applies to all init > systems because shell is so powerful on unix.
Stop thinking in sshd. I can write the *whole* daemon in shell, not in another script file, but inside /etc/init.d/mystupiddaemon (or /etc/rc.whatever); shell is Turing-complete, I can write in it anything I can write in C (or in assembler, or machine code). In that sense, the init system (which uses shell for launching daemons) can be used to determine *how* the daemon behaves (because it uses shell for launching daemons). You can't do that with systemd; there is a clear and unavoidable separation between the starting/stoping/monitoring of daemons, and the daemons themselves. Such distinction doesn't really exists in SysV nor OpenRC (since they use shell, a Turing-complete language, for launching daemons), and therefore you can mixup everything. I agree, it doesn't necessarily means that it *will* happen; but even the possibility is frigthning for a system administrator in a production server. With systemd, that possibility *doesn't exist* (because it doesn't uses a Turing-complete language to start/stop/monitor daemons). Like the clear separation between content and presentation in webapps, or between the model and the view in the MVC design patter, having a clear separation between how you start/stop/monitor your daemon, and what the daemon does, is a good thing. If you don't agree with that, well, we must agree to disagree. Regards. -- Canek Peláez Valdés Posgrado en Ciencia e Ingeniería de la Computación Universidad Nacional Autónoma de México
