Question

1)Consider a file system in which a file can be deleted and its disk space reclaimed while links to that file still exist. What problems may occur if a new file is created in the same storage area or with the same absolute path name? How can these problems be avoided?

2)Consider a file systemthat uses a modified contiguous-allocation scheme with support for extents.A file is a collection of extents, with each extent corresponding to a contiguous set of blocks. A key issue in such systems is the degree of variability in the size of the extents. What are the advantages and disadvantages of the following schemes? a. All extents are of the same size, and the size is predetermined. b. Extents can be of any size and are allocated dynamically. c. Extents can be of a few fixed sizes, and these sizes are predetermined.

3)If all the access rights to an object are deleted, the object can no longer be accessed. At this point the object should also be deleted, and the space it occupies should be returned to the system. Suggest an efficient implementation of this scheme

4)What commonly used computer programs are prone to man-in-the-middle attacks? Discuss solutions for preventing this form of attack.

5)Discuss the following with neat diagrama.

Virtualization and its types

b.Hypervisor

(Operating system ,Computer Science)

Answer 1

1)This is a good question, which addresses some corner cases that are - luckily - handled by all filesystems I’m aware of. As I saw it, you described two related but separated.

1. A file is deleted but it kept open and another file is created in the same storage area, i.e. occupying the same blocks on the disk at a same time.

This scenario can’t happen, since as long as the file is open, its inode “has a reference” to it. As long as there are references to the inode, its blocks are marked as “used”, and will not be allocated to another file.

Once the file is closed and there are no more references to the inode, the blocks are marked as “free” and can be allocated to another file.
BTW, this is how different “undelete” utilities work - as long as the blocks haven’t been allocated to another file, the original file’s contents can be recovered.

2. A file is deleted and another file is created with the same name in the same directory.

This is an acceptable scenario, since as soon as the file is deleted (even if it’s still kept open), its directory entry is removed - which allows another file to be created with the same name under the same directory.

Note that this new file will be a separate file with a different index node and will occupy different blocks (once those are allocated to it) - the only similarity will be the file name, which will not be in use at the time of the new file’s creation

4)A man in the middle (MITM) attack is a general term for when an attacker positions himself in a conversation between a victim either to eavesdrop or to impersonate one of the victims, making it appear as if a normal exchange of information is underway.

The goal of an attack is to steal personal data, such as login credentials, account details and credit card numbers. Targets are typically the victims of financial applications, SaaS businesses, e-commerce sites and other websites where logging in is required.

Data obtained during an attack could be used for many purposes, including identity theft, unapproved fund transfers or an illicit password change.

Blocking MITM attacks requires some practical steps on the part of victims or users, as well as a combination of encryption and verification methods for applications.

For users, this means:

Avoiding open WiFi connections that are not password protected.
Paying attention to browser notifications visiting a website as being unsecured.
Instantly logging out of a secure application when it’s not in use.
Not using public networks (e.g., coffee shops, hotels) when conducting sensitive or important transactions.

5) Virtulization and its Type

Hypervisor

Due To the limitation of text, I unable to answer all question