Lab Functions

1. Create a simple file named "try" with just an "echo" command like this:
   Important: Use either the /home/square (default) directory or "cd /tmp" to use the /tmp directory. Do not use your hdrive. Network drives do not support permissions normally!

   echo echo Here in try > try
   

2. Attempt to execute your "try" command:

   try
   

   What happens? __________________________

3. What are the permissions of file try? (use "ls -l try")

   Owner: _______

   Group: _______

   Other: ______

4. Add execute permission for the owner (ourself).

     chmod u+x try
   

5. Display permissions again. What changed? _____________________

6. Attempt to execute the file again (it is a script).

   try
   

   What happened this time? _________________________

7. Add a line to the file with:

   echo echo Second command >> try
   

8. Execute the "try" command again. What happens? _______________

9. Remove write permission for the user.

   chmod u-w try
   

10. Now attempt to add a third line to the file:

    echo echo Third one >> try
    

    What happens? _____________________

11. Check the permissions of the "grep" command file. The name is /bin/grep.

    Who owns the file? ________________________

    What are the permissions for other users (like you)? __________

    Can you write to the file? _________________ (you can try with "echo junk >> /bin/grep").

12. Make /tmp your current directory. We will create some files and work with permissions.

    Now make a new subdirectory in /tmp named /tmp/ptest. (e.g. if /tmp is your current directory, mkdir ptest).

    Make /tmp/ptest your current directory.

13. Create a file named /tmp/ptest/p1 using echo or vi.

    What userid owns the file? _______________________

    What group has group ownership of the file? _____________________

14. Make the permissions on the file 600 (6=rw) with:

    chmod 600 p1
    

    See text for use of numeric permissions.

15. Prove to yourself that you can read (e.g. vi) and write (e.g. echo with >> or vi and save) the file.

16. Change the owner of the file p1 to "extra". Try the chown command without sudo. What happens? ___________________________

    Now use sudo to change ownership of p1 to "extra". (e.g. sudo chown extra p1.

17. Use ls -l to verify ownership. What are the permissions?

    ________________________

18. Try to read from the file p1 (using (cat or vi).

    What happens? __________________________

19. Try to write to the file p1 (using echo or vi).

    What happens? __________________________

20. Do these functions. Write the command you use for each function:
    1. Make /tmp your current directory: ________________________

    2. Make a new directory in /tmp: _________________________

    3. Make the permissions on the directory drwxr--r-- _____________________________________

    4. Change the ownership of the directory to userid "extra". ___________________________________________

    5. Try to make your new directory the current directory.

       Command: ______________________________

       What happens: ____________________________________

    6. Change the permissions on the directory to drwxr-xr-x (you will need to use sudo since your userid, "square", is no longer the owner). ____________________________________

    7. Now make the directory your current directory. ___________________________

    8. Try to create a file (e.g. vi or echo) in this directory. _________________________________

       What happens? _____________________________________

       Why? ____________________________________

To Turn in

This handout with answers filled in (handwritten).