ICT246: Usage of Virtual Machine is Getting more Important in the Modern World: Operating Systems Assignment, SUSS, Singapore

Question 1
(a) Usage of virtual machine is getting more important in the modern world. Determine and explain whether Type 1 or Type 2 hypervisor is more suitable for the following scenario.

“A company has recently purchased a high-end physical server, and the server is to be used to host 4 virtual machines. 2 virtual machines will be running Redhat Enterprise Linux which will be used for a real-time system. The other 2 virtual machines will be running Windows Server 2019 Standard and will be used for training purposes.”

(b) File management uses different file allocation methods. Two of the file allocation methods are chain allocation method and contiguous allocation method.

Referring to Figure Q1(b), which the shaded blocks indicate blocks that are already used by existing files. Figure Q1(b)

Sketch and demonstrate how the disk diagram (with a file allocation table that only indicates the new file) looks like if a new file that has a length of 6, and starts at block 1, are to be written to the disk for each of the following method.

(i) chain allocation method

(ii) contiguous allocation method

State your reasons if the new file cannot be written to the disk.

(c) Contrast the following two devices on their “operating system” using the ability to evolve the objective of the operating system.
– A traditional microwave oven
– An iPad

Question 2

(a) Create ONE (1) bash shell script (using a “for” loop) to implement the following tasks which are related to file and folder access control. All the tasks need to be implemented inside the “for” loop and the root user will execute the bash shell script.

• Create THREE (3) files (Happy1, Happy2, Happy3) in the current folder
• Write today’s date (with the format of YYYY-MM-DD) in each of the file
• Append another line “keep a 2m distance” in each of the file
• Change the owner of the file to ‘Tony’ (assume that there is a user “Tony” and you do not have to create this user)
• Change the permission of each file such that the owner can read, write and execute, the group can read and write, whereas all others can read
• Move each of the file to the /tmp folder if the file does not already exist in /tmp
• Display the owner and permissions of file Happy2 in the /tmp folder (only display once for the execution of the whole script)

(b) Two countermeasures to security threats are authentication and access control. Justify the validity of the following statement.
“Authentication system is useless without access control system”

Question 3

(a) Paging is an important concept in memory management. Sketch the page tables for process A, B, C, D and free frame list for Figure Q3(a).

Figure Q3(a)
(b) Short-term scheduling determines which process will be executed by the processor. Illustrate by sketching the execution pattern to describe the Shortest Remaining Time scheduling algorithm by referring to Table Q3(b).

Question 4

(a) Explain why programmed I/O is slow by using an example.

(b) A server comes with 5 hard disks and each hard disk is having a storage size of 500GB.

Calculate the usable space (in TB, 2 decimal places) if the server is using the following RAID system.
(i) RAID 0
(ii) RAID 5
(iii) RAID 6

(c) Contrasting the different layers of an OS involves understanding the different layers. Hard disk is an example in the hardware layer that is controlled by the OS. Ability to calculate metrics related to hard disk is thus an important task.

A disk is having an average seek time of 6 ms, and 2000 sectors per track with each sector having 512 bytes. The total time to read a file of 1000 sectors is 22 ms. Calculate the rotational speed of the disk in rps (revolution per second).

Question 5
(a) Executing system tasks in Linux OS include configuring and monitoring of disk quota.

A company Optimus Prince Pte Ltd has recently configured a Debian Server with ZFS installed. The server contains five hard disks (sda, sdb, sdc, sdd, sde) with Debian OS installed in one of the hard disks (sda). Each Hard disk is having the size of 1TB.

Optimus Prince Pte Ltd wants to perform the following tasks in sequence using ZFS

– Create a pool (use your initial as pool name) using RAID 5 for the remaining four hard disks
– Create two file systems (use “social”, “distance” as filesystem name) under the pool
– Set a disk quota of 500GB to “distance”
– Set a disk reservation of 800GB to “social”
– Check the quota of the file system “distance”
– Check the reservation of the file system “social”
Create the set of commands to help you fulfil the above tasks.

(b) Android is frequently compared with iOS, and it is the most widely used mobile OS.

Discuss the correctness of the following sentences on Android OS.

“I’m using an Android mobile phone and the kernel is similar to the standard Linux kernel. The Android kernel is usually bigger as it has enhanced the kernel with features that are tailored to the mobile environment. The Android system libraries contain an activity manager that manages the lifecycle of applications.