COMP 3000 Midterm exam 2010 - Revision history

Soma: /* Question 8 */

2010-11-09T14:11:17Z

Question 8

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	Q: What are three events that cause signals to be sent in UNIX?		Q: What are three events that cause signals to be sent in UNIX?

	A:		A: child process exit, divide by zero, suspend/resume process (STOP, CONT), terminate (TERM), really kill (KILL), many others

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2010-11-09T14:04:27Z

Question 7

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	Q: A solution to the producer/consumer problem must take into account many conditions. What are three of them?		Q: A solution to the producer/consumer problem must take into account many conditions. What are three of them?

	A:		A: Consumer runs out of things to consume, producer runs out of space to produce in, and to prevent the producer and consumer from accessing the same memory at the same time (corrupting the shared data structure). (Note both synchronization and mutual exclusion is required.)

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2010-11-09T13:57:55Z

Question 5

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	Q: When a process becomes undead (a zombie), who can send it to its grave permanently? What must it do?		Q: When a process becomes undead (a zombie), who can send it to its grave permanently? What must it do?

	A: The ~~ancestor of all programs is <code>init</code>~~ (~~PID = 1), and~~ its ~~job is to kill off any zombie~~ children ~~not properly killed~~ by ~~their parents before their own deaths~~. ~~Gruesome stuff~~.		A: The process's parent. (When a process dies its children are adopted by init.) The parent calls wait or waitpid to get the zombie's return value.

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2010-11-09T13:55:34Z

Question 4

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	Q: Why doesn't <code>ldd</code> report all the libraries that are listed in /proc/<PID>/maps?		Q: Why doesn't <code>ldd</code> report all the libraries that are listed in /proc/<PID>/maps?

	A: The <code>ldd</code> command only lists libraries that ~~were statically~~ linked at ~~compile time~~. The proc mapping lists those and the ones ~~linked dynamically~~ at runtime.		A: The <code>ldd</code> command only lists libraries that are dynamically linked and needed at program start. The proc mapping lists those and the ones loaded at runtime (plus other memory mapped files).

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2010-11-09T13:50:44Z

Question 3

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	''Path to executable:'' <code>/bin/chmod</code> (partly derived ... see note below)<br>		''Path to executable:'' <code>/bin/chmod</code> (partly derived ... see note below)<br>
	''Arguments:'' <code>a+r</code> <code>foo.txt</code><br>		''Arguments:'' <code>chmod</code> <code>a+r</code> <code>foo.txt</code><br>
	''Environment:'' (not shown ... depends on the shell)		''Environment:'' (not shown ... depends on the shell)

2010-11-09T13:47:59Z

Question 1

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	Q: On an x86-class processor that supports hardware virtualization, it is possible in principle to virtualize any OS that can run on the native hardware. In practice, only certain operating system types and versions will run well on a given VM platform (e.g., VirtualBox, VMWare Player). What is one reason for this discrepancy?		Q: On an x86-class processor that supports hardware virtualization, it is possible in principle to virtualize any OS that can run on the native hardware. In practice, only certain operating system types and versions will run well on a given VM platform (e.g., VirtualBox, VMWare Player). What is one reason for this discrepancy?

	A:		A: - lack of VM guest drivers (either VM specific or for simulated hardware)


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2010-10-31T13:34:21Z

clarity

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	Q: UNIX files each have permissions for three classes of users. What are those classes?		Q: UNIX files each have permissions for three classes of users. What are those classes?

	A: Owner, Group, Others. A file is typically created with owner set to the user running the program and the group set to that user's primary group. The value of the permissions (i.e. _rw_rw_r__) is ~~set~~ by the <code>umask</code> command. ~~They~~ can be changed after file creation with the <code>chown</code> command.		A: Owner, Group, Others. A file is typically created with owner set to the user running the program and the group set to that user's primary group. The value of the specific permissions (i.e. _rw_rw_r__) is determined at file creation by prior use of the <code>umask</code> command. Permissions can be changed after file creation with the <code>chown</code> command.

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2010-10-28T03:48:21Z

Question 6

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	==Question 6==		==Question 6==
	Q: UNIX files each have permissions for three classes of users. What are ~~they~~?		Q: UNIX files each have permissions for three classes of users. What are those classes?

	A: Owner, Group, Others. A file is typically created with owner set to the user running the program and the group set to that user's primary group. The value of the permissions (i.e. _rw_rw_r__) is set by the <code>umask</code> command. They can be changed after file creation with the <code>chown</code> command.		A: Owner, Group, Others. A file is typically created with owner set to the user running the program and the group set to that user's primary group. The value of the permissions (i.e. _rw_rw_r__) is set by the <code>umask</code> command. They can be changed after file creation with the <code>chown</code> command.

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	~~--[[User:Jjpwilso\|Jjpwilso]] 14:19, 27 October 2010 (UTC) This question was truncated from what we had on the midterm. I tacked on "What are they?" Was there something else here?~~

	==Question 7==		==Question 7==

2010-10-28T03:46:54Z

Question 4

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	==Question 4==		==Question 4==
	Q: Why doesn't <code>ldd</code> report all the libraries that are listed in /proc/$<$PID$>$/maps?		Q: Why doesn't <code>ldd</code> report all the libraries that are listed in /proc/<PID>/maps?

	A: The <code>ldd</code> command only lists libraries that were statically linked at compile time. The proc mapping lists those and the ones linked dynamically at runtime.		A: The <code>ldd</code> command only lists libraries that were statically linked at compile time. The proc mapping lists those and the ones linked dynamically at runtime.

2010-10-27T14:53:33Z

formatting

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	==Question 17==		==Question 17==
	Q: Describe a race condition error and a test that would catch that error in testing. (You may describe a ``well-known'' race condition or one that you make up.)		Q: Describe a race condition error and a test that would catch that error in testing. (You may describe a ''well-known'' race condition or one that you make up.)

	A:		A: