copy from one folder to another not working in terminal

Question

I'm new to Ubuntu. I installed it because i'm using it in my operating systems class in college. One thing needed to do is copy. This is the lecturers notes on how to do this:
Change to your home directory

cd

Display a listing of the files contained within it in long format

ls -al

Make a directory here called test

mkdir test

Below test create two directories x and y

cd test
mkdir x
mkdir y

Copy the file fstab from the /etc directory to the directory y

cd y
cp /etc/fstab .

But it's not working. Can anyone help me with this?

Answer 1

In order to copy a file you must have read permission on the parent directory of the file and write permission on the destination.

Think of directory as a container with a lock and file as contents of the container.

You must have an access to the keys of the lock in order to access the file inside the directory(container).

File Permissions:-

r - can read the file.

w - can write to a file.

x - can run the file as a program.

Directory Permissions:- 

r - can read the contents of the directory.

w - can make changes to files inside the directory/ add or delete the files.

x - can cd to a directory.

Directory permissions are important and can override the file permissions.

Even if you're file doesn't have read permissions but the parent directory of the file has a read permission than you can copy the file assuming that you're copying the file to a location where you can write.

I assume this might be helpful.