Differences between System V and BSD in Linux

Linux or Unix has two startup modes: System V and BSD.

The biggest difference is that System V can define which services to start for different running levels, such:
#0-stop (do not set initdefault to 0)
#1-single-user mode
#2-multiple users, but no NFS
#3-full multi-user mode (unbounded black box)
#4-useless
#5-X11 (graphic interface)
#6-Restart (do not set initdefault to 6)
The Startup Mode of System V can be flexibly defined to start the FTP service at the running level 3, but not at the running level 5.
Using BSD has no concept of running level.

Different startup scripts:

BSD Startup Mode: in/etc/rc. d and/usr/local/etc/rc. d. in Conf, set xxx_enable = "yes" or xxx_enable = "no" to start or stop the service with the system. The file is/etc/defaults/RC. A subset of conf. The BSD startup method has no running level, which is simple but lacks diversity.

System V Startup Mode: that is, the Linux Startup Mode. The script for starting the service is stored in/etc/rc. d/init. d. the d directory contains many directories similar to rc0.d or rc2.d. This defines the directories of services to be started for each different running level. The number 0 1 2 indicates the running level, access these directories and you will see many linked files. Files starting with S or K indicate whether to enable the Service at the current running level. These files are linked to/etc/rc respectively. d/init. d/Many executable files below.


Note: In some operating systems in System V Startup Mode (such as redhat9), except for/etc/rc. d/init. d/directory, and/etc/init. d/This directory, in fact, LS-l, you can see,/etc/init. d/The Directory is originally linked to/etc/rc. d/init. d.
From: http://f543711700.iteye.com/blog/1167656