UNIX treats file directories in the same fashion as files; that is, both are defined by the same type of data structure, called an inode. As with files, directories include a nine-bit protection strong. If care is not taken, this can create access control problems. For example, consider a file with protection mode 644(octal) contained in a directory with protection mode 730. How might the file be compromised in this case? What can we do to stop this vulnerability without changing the protection mode 730 for the directory?

The following four requests could come in to an operating system as it is running on a computer system: The clock in the computer has just “ticked,” and we need to update a seconds counter. The program running on processor 2 is trying to perform an illegal operation code. Someone pulled the plug on the power supply, and the system will run out of power in 50 msec. The disk has just read the character that passed under the read/write head, and it wants to store it in memory before the next one arrives. In what order should the operating system handle these requests?

For this assignment, write a pair of programs, in C or as shell scripts, to send and receive a message. Your programs will: Send and receive a message by a covert channel on a MINIX 3 system. Hint: A permission bit can be seen even when a file is otherwise inaccessible, and the sleep command or system call is guaranteed to delay for a fixed time, set by its argument. Measure the data rate on an idle system. Create an artificially heavy load by starting up numerous different background processes and measure the data rate again.

Assuming 4K clustering for a 500-byte file, what is the size (in bytes) of the File Slack? O 12 bytes O 1536 bytes O 3584 bytes O 4096 bytes

Minix Suppose a file is on a filesystem using a 1K block size. This file is maintained on thedisk using i-nodes as is typical on many UNIX filesystems (as described on pages 286-287 and789-790 of your text). Suppose there are seven direct pointers, and then a pointer to one singlydirect block, a pointer to a doubly indirect block, and a pointer to a triply indirect block. Suppose aprogram creates and opens a file in this filesystem, and then seeks to the following positions,writes a character, and then exits. Identify how many disk blocks, (both data and indirect blocks)must be allocated to store the data for the file. (Note that a-c each represent a different file.)a. Seek to 9000b. Seek to 300000c. Seek to 67,000,000How big would a file need to be to require the triply indirect pointer?

Load infile using one byte per channel and save it as a PNG, using outfile for the file name. Use one byte per channel. graphics.cpp 1 #define STB IMAGE IMPLEMENTATION 2 #define STB IMAGE WRITE IMPLEMENTATION #include "stb_image.h" #include "stb_image_write.h" 3 4 #include #include 7 using namespace std; 8 9. int main() 10 { string infile = "pete.png"; string outfile = "out.png"; 11 12 13 14 15 16 17 } CodeCheck Reset

Given the following data file: STUDENT(ID, SNAME, ADDRESS, LEVEL, GPA, …) Suppose that: record size R = 200 bytes block size B = 512 bytes r = 2000 records            Then, Find out: Blocking factor(Bfr)   Bfr=B/R  Number of file blocks(b)   b=r/bfr

- Let's assume that a system can handle 2,000 users. a UNIX security system that permits 1,990 users to view a single file called "MPX.pdf" is suggested. Do you have any plans for the other ten people who don't have access to the file?

What would happen if a directive were disregarded? In the following circumstances, a software-managed TLB is faster than a hardware-managed TLB:

The beginning of a free space bitmap looks like this after the disk partition is first formatted: 1000 0000 0000 0000 (the first block is used by the root directory). The system always searches for free blocks starting at the lowest-numbered block, so after writing file A, which uses six blocks, the bitmap looks like this: 1111 1110 0000 0000. Show the bitmap after each of the following additional actions: (A) File A is deleted (B) File C is written, using eight blocks (C) File B is deleted.