1. Examine all options of programs 'chage', 'useradd' and 'adduser'.

 2. Create user 'mrkva' ('carrot', but in slovak;) and make the system to ask the
    user to set his password after his/her first logon (but to not ask any
    password to log in).

 3. Create group 'zelenina' (Slovak 'vegetables', for that matter;) and
    users 'mrkva' (you know that already), 'kapusta' (cabage), and 'zajac'
    (rabbit) the way that only 'mrkva' and 'kapusta' can work with directory
    'zahrada' (garden) and all its subdirectories. Other users (e.g.
    'zajac'/rabbit) can work with these directories only if they know
    password for the group 'zelenina'.

    Quite useful can be commands 'gpasswd', 'sg' and 'newgrp'. First of them
    allows you to set password for a group, another two allow user to run
    some program (e.g. new shell) with permissions extended by permissions
    of some group -- of course, only if they enter correct group password.
    If you had not seen them yet, manual page will tell you more.
 
 4. Meet program 'id' :) (hint: 'man id'). As user 'mrkva' copy program 'id'
    to your home directory and set its SUID or SGID attribute. Now, as user
    'zajac', run 'id' from the home directory of user 'mrkva'. Try all
    variations.

    Note: Try changing group of copied program to 'zelenina'. How will this
    affect output of this program?

 5. In the directory 'zahrada' create "secret" file and name it 'foliovnik'
    (greenhouse). This "secret" file should be created the way that you
    modify directory 'zahrada', so no one except 'mrkva' and 'kapusta' (so
    also not 'zajac') could delete, rename, or even know of existence of
    this file. We want to assure that anyone (also 'zajac'), who knows name
    of this file could edit it. Also, both 'mrkva' and 'kapusta' should be
    able to rename this "secret" file.

47. A question for gurus: What do you think, which of above mentioned users
    is root? ;o))