Web server address - # for I in `echo $*` do for
# for I in `echo $*` do for J in 15 2 1 9 do kill -$J $I && sleep 1 done done exit 0 This script cycles through a list of process IDs specified on the command line. To ensure that the process has been terminated, several signals are sent to the process in increasing levels of severity. The first signal attempted is 15 (signal number 15 is SIGTERM), which requests the termination of the process. The next signal is 2 (signal 2 is SIGINT), representing an attempted interrupt from the keyboard (i.e., a Ctrl+C sequence or similar action). Signal 1, SIGHUP, is then tried, which attempts to kill the process by indicating that the controlling terminal has “hung up,” terminology left over from when serial consoles were more prevalent. Finally, signal 9, SIGKILL, is sent to the process. This last resort signal doesn t allow the process to perform any activities on exiting it just tries to “kill with impunity.” A one-second delay, induced only if previous attempts to kill the process have failed, gives the process some time to trap each signal and exit properly. For a complete list of signals, refer to the signal 7 manual page (type man 7 signal). More advanced scripts are examined throughout the course of this chapter. System Initialization In the boot process, the transfer from the kernel phase (the loading of the kernel, probing for devices, and loading drivers) to init is indicated by the following lines: INIT: version 2.78 booting Welcome to Red Hat Linux The init program, part of the SysVinit RPM package, is now in control. Known as the father of all processes, the output from ps always lists init as PID (process identifier) 1. Its actions are directed by the /etc/inittab file, which is reproduced next. The inittab file The following text shows the contents of the /etc/inittab file as it is delivered with Red Hat Linux: # # inittab This file describes how the INIT process should set up # the system in a certain run level. # # Author: Miquel van Smoorenburg,
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