There are four questions that need answering prior to awarding points: Week 4 DQ
ID: 3547819 • Letter: T
Question
There are four questions that need answering prior to awarding points:
Week 4 DQ 1
Write a short essay in which you discuss the different program errors that are likely to occur and how they should be handled within scripts.
Week 4 DQ 2
Write a 200- to 300-word response that discusses the different reasons for terminating a process and the commands used for this purpose.
Week 4 DQ 3
Compare and contrast using the command line versus a graphical user interface (GUI) for systems administration functions. What are the advantages and disadvantages of each?
Week 4 DQ 4
What are the advantages and disadvantages to the large number of Linux variants? Which Linux variants might be most advantageous in a business environment? Explain your reasoning.
Explanation / Answer
There are several commands that can be used to control processes. They are:
While it may seem that this subject is rather obscure, it can be very practical for the average user who mostly works with the graphical user interface. You might not know this, but most (if not all) of the graphical programs can be launched from the command line. Here's an example: there is a small program supplied with the X Windows system called xload which displays a graph representing system load.
While the kill command is used to "kill" processes, its real purpose is to send signals to processes. Most of the time the signal is intended to tell the process to go away, but there is more to it than that. Programs (if they are properly written) listen for signals from the operating system and respond to them, most often to allow some graceful method of terminating. For example, a text editor might listen for any signal that indicates that the user is logging off, or that the computer is shutting down. When it receives this signal, it saves the work in progress before it exits. The kill command can send a variety of signals to processes. Typing:
will give you a list of the signals it supports. Most are rather obscure, but several are useful to know:
Signal #
Name
Description
Hang up signal. Programs can listen for this signal and act (or not act) upon it.
Interrupt signal. This signal is given to processes to interrupt them. Programs can process this signal and act upon it. You can also issue this signal directly by typing control-c in the terminal window where the program is running.
Termination signal. This signal is given to processes to terminate them. Again, programs can process this signal and act upon it. You can also issue this signal directly by typing control-c in the terminal window where the program is running. This is the default signal sent by the kill command if no signal is specified.
Kill signal. This signal causes the immediate termination of the process by the Linux kernel. Programs cannot listen for this signal.
Signal #
Name
Description
1 SIGHUPHang up signal. Programs can listen for this signal and act (or not act) upon it.
2 SIGINTInterrupt signal. This signal is given to processes to interrupt them. Programs can process this signal and act upon it. You can also issue this signal directly by typing control-c in the terminal window where the program is running.
15 SIGTERMTermination signal. This signal is given to processes to terminate them. Again, programs can process this signal and act upon it. You can also issue this signal directly by typing control-c in the terminal window where the program is running. This is the default signal sent by the kill command if no signal is specified.
9 SIGKILLKill signal. This signal causes the immediate termination of the process by the Linux kernel. Programs cannot listen for this signal.
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