Cat rcS
root:/etc/init.d# cat rcS
#!/bin/sh
Start all init scripts in /etc/init.d
executing them in numerical order.
for i in /etc/init.d/S??* ;do
Ignore dangling symlinks (if any).
! -f "$i" \] \&\& continue case "$i" in \*.sh) # Source shell script for speed. ( trap - INT QUIT TSTP set start . $i ) ;; \*) # No sh extension, so fork subprocess. $i start ;; esac done rcS 当系统启动时： 内核运行 /sbin/init init 根据 /etc/inittab（或内置逻辑）决定进入 sysinit 阶段 调用 /etc/init.d/rcS rcS 遍历 /etc/init.d/S??*，依次执行： /etc/init.d/S01syslogd start /etc/init.d/S02klogd start /etc/init.d/S02sysctl start ... /etc/init.d/S46network start ← 此时 ifup -a 才真正运行！