Process Management

Question 1

What is a process?

Answer 1

Process is a running program.

Question 2

What does process include?

Answer 2

Binary, instance of VM, open files, one or more threads, associated user …

Question 3

What is a thread?

Answer 3

Thread is a unit of activity inside a process.

Question 4

What does each thread have?

Answer 4

Its own stack, registers and instruction pointer.

Question 5

How do we call a unique value assigned to each process?

Answer 5

Process id.

Question 6

What is the first process started after booting?

Answer 6

The init process.

Question 7

What is the pid of init process?

Answer 7

1.

Question 8

What are some of the prefered locations of init process?

Answer 8

/sbin/init, /bin/init, /etc/init

Question 9

How does the kernel behave if it can not find the init process?

Answer 9

It halts the system.

Question 10

What is the default maximum value that can be assigned as process id?

Answer 10

32768.

Question 11

How can we change the default maximum value for process id?

Answer 11

By modifying /proc/sys/kernel/pid_max.

Question 12

How does kernel allocate process ids?

Answer 12

In a linear fashion.

Question 13

What is a parent process?

Answer 13

A process that starts a new process.

Question 14

What is a child process?

Answer 14

Process spawned by some parent process.

Question 15

What does child inherit from parent in terms of resource management?

Answer 15

Parents user and group ownerships.

Question 16

What are the two steps to run a new process programatically?

Answer 16

Call to fork() followed by one of exec* calls to load the new binary.

Question 17

What does exec* function do?

Answer 17

Loads a binary image into memory by replacing currently loaded image of the running process.

Question 18

In a function execvp, what does v and p represent?

Answer 18

V denotes that a function accepts an array of arguments while p denotes that “file” argument is part of user path.

Question 19

How does exec behave on failure?

Answer 19

It returns -1 and sets an errno.

Question 20

What does fork do?

Answer 20

Creates a new process as a near duplicate of its parent.

Question 21

What does fork return to the child process?

Answer 21

0.

Question 22

What does fork return to parent process?

Answer 22

Pid of the child process.

Question 23

What is mean by copy-on-write (COW)?

Answer 23

Instead of duplicating parent resources to child process, both processes share the same resources until the moment one of the process tries to modify the resources. On first modification the process is given a resource duplicate.

Question 24

What is a zombie process?

Answer 24

Zombie is a process which is no longer running but can be found in a process table because the parent is waiting for the result of its execution.

Question 25

What is an orphan process?

Answer 25

Process whos parent is no longer running.