Answers of 6 questions from problem set 3 about linux user and group permission.

linuxuser.txt

1.  
For adding a new user, in this case which
is 'mahabub', I will use 'adduser'.
Also I will put the 'gecos' option in order to 
do the task non-interactively.

command:    adduser --disabled-password --gecos "" mahabub

2.
In order to grant root permission to the user
mahabub I need to edit a file. using the 'visudo'
command I can open that file. And then grant root permission
to the user mahabub in a wayso that he doesn't have 
to use password.

command:    sudo visudo
            mahabub ALL=(ALL) NOPASSWD:ALL

3.
I will use 'mkdir' command for making a .ssh folder in user's (mahabub's)
home directory.

command:    mkdir /home/mahabub/.ssh

4.
I will use 'touch' command for making a .ssh folder in user's (mahabub's)
home directory

command:    touch /home/mahabub/.ssh/id_rsa

5.
In order to grant the READ-ONLY permission to a user which is not root i will
use 644 (rw-r--r--) permission which is read write for owner, read only for group and user. 

command:    chmod 644 /home/mahabub/.ssh/id_rsa

6.
I will use 'chown' command to chage the owner of the directory. Also use -R
option in order to make it applicable for all files.

command:    sudo chown -R mahabub:group /home/mahabub