Operating Systems Assignment ​ ​10 ​-​ ​Part ​One Solution

CS 3423 Operating Systems

Assignment 10 - Part One
● The programming assignment will be posted separately with its own due date.
1. [30 points] Problem Set
1. [20 points] 11.2 Contrast the performance of the three techniques for allocating disk
blocks (contiguous, linked, and indexed) for both sequential and random file access.
You must elaborate to receive full credit.
2. [10 points] 11.8 Consider a file system that uses inodes to represent files. Disk
blocks are 8 KB in size, and a pointer to a disk block requires 4 bytes. This file
system has 12 direct disk blocks, as well as single, double, and triple indirect disk
blocks. What is the maximum size of a file that can be stored in this file system?
You must show your calculation to receive credit.
2. [30 points] Programming Problems
Strictly speaking, this is not really a programming problem, but more like an interactive
experimentation.
11.13 [modified preparation instruction] Before starting this problem, create two text files
named file1.txt, file3.txt (but not file2.txt !!) in a Unix or Linux-like system (i.e.,
uses inodes in its file system) with unique contents. Next, obtain the inode number of this file
with the command
ls -li file1.txt
This will produce output similar to the following:
16980 -rw-r--r-- 2 os os 22 Sep 14 16:13 file1.txt
where the inode number is boldfaced. (The inode number of file1.txt is likely to be
different on your system.)
The UNIX ln command creates a link between a source and target file. This command
works as follows:
ln [-s] <source file <target file UNIX provides two types of links: (1) hard links and (2) soft links. A hard link creates a
separate target file that has the same inode as the source file. Enter the following command
to create a hard link between file1.txt and file2.txt:
ln file1.txt file2.txt
2.1 [5 points]
What are the inode values of file1.txt and file2.txt? Are they the same or different? Do
the two files have the same—or different— contents?
2.2 [5 points]
Next, edit file2.txt and change its contents. After you have done so, examine the
contents of file1.txt. Are the contents of file1.txt and file2.txt the same or different?
2.3 [5 points]
Next, enter the following command which removes file1.txt:
rm file1.txt
Does file2.txt still exist as well?
2.4 [5 points]
Now examine the man pages for both the rm and unlink commands. Afterwards, remove
file2.txt by entering the command
strace rm file2.txt
The strace command traces the execution of system calls as the command rm file2.txt
is run. What system call is used for removing file2.txt?
2.5 [10 points]
A soft link (or symbolic link) creates a new file that “points” to the name of the file it is linking
to. In the source code available with this text, create a soft link to file3.txt by entering the
following command:
ln -s file3.txt file4.txt
After you have done so, obtain the inode numbers of file3.txt and file4.txt using the
command
ls -li file*.txt
Are the inodes the same, or is each unique? Next, edit the contents of file4.txt. Have the
contents of file3.txt been altered as well? Last, delete file3.txt. After you have done
so, explain what happens when you attempt to edit file4.txt.3. Programming Exercise - to be posted separately with its
own due date