Operating Systems 2021F: Assignment 3 - Revision history

Soma at 15:10, 30 November 2021

2021-11-30T15:10:27Z

← Older revision		Revision as of 15:10, 30 November 2021
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	chroot .		chroot .
	</syntaxhighlight>		</syntaxhighlight>

			==Solutions==

			[https://homeostasis.scs.carleton.ca/~soma/os-2021f/solutions/assign3-sol.txt Assignment 3 solutions]

Soma at 02:57, 23 November 2021

2021-11-23T02:57:47Z

← Older revision		Revision as of 02:57, 23 November 2021
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	Please submit the answers to the following questions via Brightspace by November 22, 2021 by 11:59 PM. There are 20 points in 10 questions (and one 4 point bonus question).		Please submit the answers to the following questions via Brightspace by November <del>22</del> 28, 2021 by 11:59 PM. There are 20 points in 10 questions (and one 4 point bonus question).

	Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2021f/templates/comp3000-a3-template.txt this template]. Name your answer file "<username>-comp3000-assign3.txt" (where username is your MyCarletonOne username).		Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2021f/templates/comp3000-a3-template.txt this template]. Name your answer file "<username>-comp3000-assign3.txt" (where username is your MyCarletonOne username).

Soma: /* Tasks/Questions */

2021-11-20T04:03:44Z

Tasks/Questions

← Older revision		Revision as of 04:03, 20 November 2021
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	# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.		# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.
	# [2] Copy and make nano work in the new environment. What files did you have to copy to get it to work? How did you know to copy them?		# [2] Copy and make nano work in the new environment. What files did you have to copy to get it to work? How did you know to copy them?
	# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "login confined" and be logged in as the user confined.		# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "login confined" and be logged in as the user confined. Confirm this by running whoami.
	# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?		# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?
	# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!) Rather than use openssh as ubuntu uses by default, you may want to try dropbear. Don't install it on the VM using apt, though, as that could mess up regular ssh access.		# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!) Rather than use openssh as ubuntu uses by default, you may want to try dropbear. Don't install it on the VM using apt, though, as that could mess up regular ssh access.

Soma: /* Tasks/Questions */

2021-11-20T04:02:17Z

Tasks/Questions

← Older revision		Revision as of 04:02, 20 November 2021
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	# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.		# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.
	# [2] Copy and make nano work in the new environment. What files did you have to copy to get it to work? How did you know to copy them?		# [2] Copy and make nano work in the new environment. What files did you have to copy to get it to work? How did you know to copy them?
	# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "~~su -~~ confined" and be logged in as the user confined.		# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "login confined" and be logged in as the user confined.
	# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?		# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?
	# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!) Rather than use openssh as ubuntu uses by default, you may want to try dropbear. Don't install it on the VM using apt, though, as that could mess up regular ssh access.		# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!) Rather than use openssh as ubuntu uses by default, you may want to try dropbear. Don't install it on the VM using apt, though, as that could mess up regular ssh access.

Soma: /* Tasks/Questions */

2021-11-14T15:51:37Z

Tasks/Questions

← Older revision		Revision as of 15:51, 14 November 2021
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	# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "su - confined" and be logged in as the user confined.		# [3] How can you add a user "confined" to 3000fs? Make sure the user also is in a new group "confined" and has a home directory /home/confined (in 3000fs). This user should only be visible when you're in 3000fs's special shell. (If you run id when you regularly log in as student to your VM, there should be no user confined.) Make sure you can run "su - confined" and be logged in as the user confined.
	# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?		# [2] How can you mount the main root filesystem inside of the confined environment? What does this say about the security properties of a chroot'd environment?
	# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!)		# '''[4 EC]''' Make sshd work inside of the confined environment, listening in on port 2222. You should be able to ssh via localhost into the confined environment. (Outside access probably won't be possible due to restrictions on openstack. Note that I haven't gotten this working yet!) Rather than use openssh as ubuntu uses by default, you may want to try dropbear. Don't install it on the VM using apt, though, as that could mess up regular ssh access.

	==Code==		==Code==

Soma at 03:58, 13 November 2021

2021-11-13T03:58:05Z

← Older revision		Revision as of 03:58, 13 November 2021
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	~~'''This assignment is not yet finalized.'''~~

	Please submit the answers to the following questions via Brightspace by November 22, 2021 by 11:59 PM. There are 20 points in 10 questions (and one 4 point bonus question).		Please submit the answers to the following questions via Brightspace by November 22, 2021 by 11:59 PM. There are 20 points in 10 questions (and one 4 point bonus question).

Soma: /* Background */

2021-11-13T03:39:18Z

Background

← Older revision		Revision as of 03:39, 13 November 2021
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	In this assignment you'll be working with a "chrooted" environment. We'll create a filesystem, mount it, populate it, and then change the current root directory to it so we can use this environment as if it was a completely separate system.		In this assignment you'll be working with a "chrooted" environment. We'll create a filesystem, mount it, populate it, and then change the current root directory to it so we can use this environment as if it was a completely separate system.

	This mini system is rather bare bones initially and many things won't work. You'll be studying how it is put together and figuring out how to add functionality.		This mini system is rather bare bones initially and many things won't work. You'll be studying how it is put together and figuring out how to add functionality. ''You should understand what every line in 3000makefs.sh does, even if there isn't a specific question about it.''

	==Tasks/Questions==		==Tasks/Questions==

Soma: /* Tasks/Questions */

2021-11-13T03:31:15Z

Tasks/Questions

← Older revision		Revision as of 03:31, 13 November 2021
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	# [2] Lines 55-59 of 3000makefs.sh is several echo commands. What are these lines doing? Do these lines relate to any other parts of the script?		# [2] Lines 55-59 of 3000makefs.sh is several echo commands. What are these lines doing? Do these lines relate to any other parts of the script?
	# [2] What are lines 26-30 for? Is it missing anything? Explain briefly.		# [2] What are lines 26-30 for? Is it missing anything? Explain briefly.
	# [2] What is the largest file we can create in the confined environment? What determines this limit?		# [2] What is the largest file we can create in the confined environment (once initialized by 3000makefs.sh)? What determines this limit?
	# [2] If you create files in the confined environment, does it reduce the space available outside of it? How do you know?		# [2] If you create files in the confined environment, does it reduce the space available outside of it? How do you know?
	# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.		# [2] Many files in our confined environment are symbolic links. How did these files get created? Why are they symbolic links and not regular files? Explain their purpose.

Soma at 03:19, 13 November 2021

2021-11-13T03:19:53Z

← Older revision		Revision as of 03:19, 13 November 2021
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	'''This assignment is not yet finalized.'''		'''This assignment is not yet finalized.'''

	Please submit the answers to the following questions via Brightspace by November 23, 2021 by ~~10 AM~~. There are 20 points in 10 questions (and one 4 point bonus question).		Please submit the answers to the following questions via Brightspace by November 22, 2021 by 11:59 PM. There are 20 points in 10 questions (and one 4 point bonus question).

	Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2021f/templates/comp3000-a3-template.txt this template]. Name your answer file "<username>-comp3000-assign3.txt" (where username is your MyCarletonOne username).		Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2021f/templates/comp3000-a3-template.txt this template]. Name your answer file "<username>-comp3000-assign3.txt" (where username is your MyCarletonOne username).
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	# [1] Run 3000makefs.sh. After 3000makefs.sh runs, you're put in a new shell where / is now the contents of 3000fs, and you can't see anything that wasn't in 3000fs. Exiting the shell gets you back to where you were. After exiting, how do you get back to the modified environment?		# [1] Run 3000makefs.sh. After 3000makefs.sh runs, you're put in a new shell where / is now the contents of 3000fs, and you can't see anything that wasn't in 3000fs. Exiting the shell gets you back to where you were. After exiting, how do you get back to the modified environment?
	# [2] Lines 55-59 of 3000makefs.sh is several echo commands. What are these lines doing? Do these lines relate to any other parts of the script?		# [2] Lines 55-59 of 3000makefs.sh is several echo commands. What are these lines doing? Do these lines relate to any other parts of the script?
	# [2] What are lines 26-29 for? Is it missing anything? Explain briefly.		# [2] What are lines 26-30 for? Is it missing anything? Explain briefly.
	# [2] What is the largest file we can create in the confined environment? What determines this limit?		# [2] What is the largest file we can create in the confined environment? What determines this limit?
	# [2] If you create files in the confined environment, does it reduce the space available outside of it? How do you know?		# [2] If you create files in the confined environment, does it reduce the space available outside of it? How do you know?
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	umount -q $MP/proc		umount -q $MP/proc
	umount -q $MP		umount -q $MP
			rm -rf $MP
	fi		fi

	~~rm -rf $MP~~
	mkdir $MP		mkdir $MP
	mount $IMAGE $MP		mount $IMAGE $MP

Soma: /* 3000makefs.sh */

2021-11-12T20:25:56Z

3000makefs.sh

← Older revision		Revision as of 20:25, 12 November 2021
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	==Code==		==Code==

	===3000makefs.sh===		===[https://homeostasis.scs.carleton.ca/~soma/os-2021f/code/3000makefs.sh 3000makefs.sh]===
	<syntaxhighlight lang="sh" line>		<syntaxhighlight lang="sh" line>
	#!/bin/bash		#!/bin/bash