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> It's not like systemd is the first system to come to that conclusion, either. [...] Earlier than that, djb also wrote an init replacement called daemontools, [...] daemontools gained svscan in 1998, and svscanboot in 2001. Years earlier, in AIX version 3.2 released in January 1992, IBM introduced its (then) new System Resource Controller. This was, and still is, a service manager that is spawned by the initial user process, that has the task of supervising daemon processes, bringing them up and down in response to administrative command, logging control activity, and notifying about failures to run. You'll find things like the srcmstr process; the startsrc, stopsrc, and lssrc commands for starting, stopping, and listing services; the whole notion of signals to control daemons (SIGTERM, SIGNORM, SIGFORCE, et al.); entry 5.2.1 in the Usenet comp.mail.sendmail FAQ which talks about how fork-and-exit-the-main-process by Sendmail breaks service management; all of the "How do I get my too-clever-for-its-own-good daemon to work with this new service management system?" discussions in the mid-1990s; and IBM's documented advice from at least as early as 1995 on how to write daemons properly, achingly familiar. One can look to mainframe and minicomputer operating systems before that, and also to Windows NT 3.1 which had the initial user process spawning the Service Control Manager, released in 1993. But in the narrow Unix+Linux worldview, credit should go to AIX for being the first operating system released where people had come to that conclusion, approaching a quarter of a century ago. |