Le 31/03/2014 20:26, Bruce Dubbs a écrit : > I've been working on rewriting Chapter 7 to incorporate systemd. I've > come up with the following text in the introduction and would like > feedback. Thanks, > > -- Bruce > > 7.1.1. System V > > System V is the classic boot process that has been used in Unix and > Unix-like systems such as Linux since about 1983. It consists of a small > program, init, that sets up basic programs such as login (via getty) and > runs a script. This script, usually named rc, controls the execution of > a set of additional scripts that perform the tasks required to > initialize the system. > > The init program is controlled by the /etc/inittab file and is organized > into run levels that can be run by the user: > > 0 — halt > 1 — Single user mode > 2 — Multiuser, without networking > 3 — Full multiuser mode > 4 — User definable > 5 — Full multiuser mode with display manager > 6 — reboot > > The usual default run level is 3 or 5. > > Advantages > > + Established, well understood system. > > + Easy to customize. > > Disadvantages > > - Slower to boot. A medium speed base LFS system takes 8-12 seconds > where the boot time is measured from the first kernel message to the > login prompt. Network connectivity is typically established about 2 > seconds after the login prompt. > > - Serial processing of boot tasks. This is related to the previous > point. A delay in any process such as a file system check, will deleay > the entire boot process. > > - Does not directly support advanced features like control groups > (cgroups), and per-user fair share scheduling. > > - Adding scripts requires manual, static sequencing decisions. > > 7.1.2. Systemd > > Systemd is a group of interconnected programs that handles system and > individual process requests. It provides a dependency system between > various entities called "units". It automatically addresses dependencies > between units and can execute several startup tasks in parallel. It > provides login, inetd, logging, time, networking services, and other tasks. > > Advantages > > + Used on many extablished distributions by default. > > + There is extensive documentation. > > + Parallel execution of boot processes. A medium speed base LFS > system takes 6-10 seconds from kernel start to a login prompt. Network > connectivity is typically established about 2 seconds after the login > prompt. More complex startup procedures may show a greater speedup when > compared to System V. > > + Implements advanced features such as control groups to manage > related processes. > > + Maintains backward compatibility with System V programs and > scripts. > > Disadvantages > > - There is a substantial learning curve. > > - Some advanced features such as dbus or cgroups cannot be diabled > if they are not otherwise needed. Systemd knows better than the user. > > - Logging is done in a binary format. Extra tools must be used to > process logs or additional processes must be implemented to duplicate > traditional logging programs. > > - Systemd violates two of the points of traditional Unix philosophy: > > Write programs that do one thing and do it well. > Write programs to work together. > Write programs to handle text streams, because that is a > universal interface. > > -You have three points in "two of the points of traditional Unix philosophy"... Maybe violates ids to strong?
- Pointers to the "extensive documentation"? - Serial processing of boot tasks is traditional in sysv, but not mandatory. One could imagine creating some Makefile style processing, (actually, Debian does, I think). Then if the equivalent of make is called with the equivalent of -jN, some parallelism could be achieved. s/extablished/established s/diabled/disabled/ Regards Pierre -- http://linuxfromscratch.org/mailman/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
