umask
Updated: 2017-01-20 00:52 EST
Do not print this assignment on paper!
- On paper, you will miss updates, corrections, and hints added to the online version.
- On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.
- On paper, scrolling text boxes will be cut off and not print properly.
23h59 (11:59pm) Saturday November 19, 2016 (end of Week 11)
WARNING: Some inattentive students upload Assignment #08 into the Assignment #07 upload area. Don’t make that mistake! Be exact.
This assignment is based on your weekly Class Notes and covers these topics:
As noted above in the Prerequisites, parts of this assignment come from your answers in Worksheet #08 PDF.
For full marks, follow these directions exactly:
These tasks must be done in your account via Remote Login to the Course Linux Server.
Do the tasks in order, from top to bottom. Do not skip steps. Most tasks are independent, but some depend on successful completion of a previous task.
READ ALL THE WORDS in each task before you begin the task, especially all the Hints and links.
Verify your own work before running the Checking Program. You won’t have a checking program at your job interview and the Checking Program is not guaranteed to check everything.
Run the Checking Program at the end of the task to grade your work and help you find some of your errors. A perfect mark from the Checking Program does not mean your answers are correct.
When you are done with this Assignment, submit the output of the Checking Program to Blackboard before the due date, following the directions given at the end of this Assignment.
You can use the Checking Program to check your work after you have completed each task.
Most task sections below require you to finish the whole task section before running the Checking Program. You may not always be able to run the Checking Program successfully in the middle of a task or after every single task sub-step. The assignment tells you where you can safely check your work.
You will create file system structure in your CLS home directory containing various directories and files. When you are finished the tasks, leave the files and directories in place on the CLS as part of your deliverables for your instructor to verify.
Assignments may be re-marked at any time on the CLS; you must have your term work available on the CLS right until term end. Do not delete any assignment work until after the term is over!
You can modify your work and check it with the Checking Program as often as you like before you submit your final mark to Blackboard. You can upload your marks to Blackboard as many times as you like before the due date. Partial marks are accepted.
Your instructor will also mark on the due date the work you do in your account on the CLS. Leave all your work on the CLS and do not modify it after you have submitted your final mark to Blackboard.
All course notes are available on the Internet and also on the CLS. You can learn about how to read and search these CLS files using the command line on the CLS under the heading Copies of the CST8207 course notes near the bottom of the page Course Linux Server.
All references to the Source Directory below are to the CLS directory ~idallen/cst8207/16f/assignment08/
and that name starts with a tilde character ~
followed by a user name with no intervening slash. The leading tilde indicates to the shell that the pathname starts with the HOME directory of the account idallen
(seven letters).
You do not have permission to list the names of all the files in the Source Directory, but you can access any files whose names you already know.
Have you completed all the prerequisites, before attempting these tasks?
As mentioned in List of Commands You Should Know, you must keep a list of command names used each week and write down what each command does. Without that list to remind you of what command names to use, you will find assignments very difficult.
Do a Remote Login to the Course Linux Server (CLS). All work in this assignment must be done on the CLS.
Base Directory: Create the CLS directory ~/CST8207-16F/Assignments/assignment08
in which you will create the files and scripts resulting from the following tasks. (You do not have to create any directories that you have already created in a previous assignment.) Spelling and capitalization must be exactly as shown:
check
check
symbolic link needed to run the Checking Program, as you did in your last assignment and as described in the section Checking Program below.This assignment08
directory is called the Base Directory for most pathnames in this assignment. Store your files and answers in this Base Directory, not in your HOME directory or anywhere else.
Use the symbolic link to run the Checking Program to verify your work so far.
You need to understand Permissions for this task.
Record the permissions you set on each of the directories and files you create in the next Part, below. You will record these permissions by copying and editing a file that you get from your instructor.
You can record each of the permissions as you create things step-by-step in the next Part below, or you can record all of the permissions after you have finished the Part below, before you run the Checking Program.
You will need to complete the next Part, below, before you can finish recording all the permissions in this Part. The two Parts go together.
abcd0001.txt
Copy the file record.txt
from the Source Directory into your own file abcd0001
.txt
(no spaces) where the text abcd0001
userid is replaced by your own eight-character userid in the file name. This file copy should be located directly under your Base Directory.
Fix the permissions on the file so that you can edit it and nobody else (group or other) has any permissions at all.
Note on the verb edit: To edit a file, you need to be able to read the contents of the file, change the contents, and write them back into the file. You do not need to execute the contents of the file unless you are editing a script file.
You will need to edit your copy of the file with a Linux command-line text editor. The VI Text Editor is recommended, since that is the universal text editor for system administrators.
abcd0001.txt
file you just created and replace the KEY
line in the file with the output of running the program named key
located in the Source Directory. When you run the key
program, give it a single argument that is the basename of the file you are editing, i.e. abcd0001.txt
Hints on replacing the
KEY
line in the file:
First, run the
key
program with the correct argument.
You can make a symlink to or alias for thekey
program and run it that way; or, you can run it using its full absolute pathname, just as you have been running the Checking Program in the same directory. The output of thekey
program with the correct argument looks similar to this:
KEY:
abcd0001 BMf8xNDc4NDU0Mjky/2NzdDgyMDdi/zEwMDP/Zm9v/w==
You must pass the
key
program one argument that is yourabcd0001.txt
basename file name. The correct output will be 1 line, 3 words, and approximately 72 characters including the newline.- Edit the
key
program output into theabcd0001.txt
file, replacing just theKEY
line that is already in that file. Edit theabcd0001.txt
file and replace theKEY
line in that file with your newkey
program output.
- You could run the
key
program and put its output into a temporary file, and then edit theabcd0001.txt
file and read in that temporary file. (You did this in VIMvimtutor
Lesson 5.4. RETRIEVING AND MERGING FILES.)- You could append the output of the
key
program to the bottom of theabcd0001.txt
file and then edit the file to delete the oldKEY
line and replace it with the new one that you appended to the bottom of the file. (VIM makes moving lines easy.)- You could also replace just the
KEY
line using the VIM!!
method from section 2.1 #10 in Worksheet #06 PDF. (This is my favourite method; this is how I would do it.)- You could copy-and-paste the
key
program output into your editor, replacing just theKEY
line in the file.
Run the Checking Program to verify your work so far.
___
” in the file with the correct three-digit numeric (octal) permission value that you use in the next Part below.Be careful not to make other accidental changes to the file. Note the word count at the bottom of the file. Your count must match exactly, at all times. If not, re-copy the file and start over.
diff
between the original and your edited version will be helpful in knowing what you changed.You need to understand Permissions for this task. Do the permissions section of Worksheet #08 PDF before continuing. Record all your answers for later quizzes.
Now you will create some directories and files, then set the correct permissions on them. The permissions to set are described below.
Because you are applying permissions to directories as a non-
root
user, be careful not to lock yourself out of directories by restricting permissions on them too soon. First, create all the file and directory structure from the top of the directory tree down, and then apply restrictive permissions afterward from the bottom of the tree upward, after you have created all the structure.If you don’t apply permissions last, from the bottom up, you will deny yourself permissions that will prevent you from entering some directories lower down. Assign permissions from the bottom toward the top.
Create this set of directories and files, and set the permissions as given. Make sure you create directories where directories are required and files where files are required.
head
head
under your Base Directory:
head
allows the group to use ls
to see the content, but the group cannot create files or cd
into the directory. The user has full permissions. Others have permission to access files if they know their names, but no permission to see or change the names. Record the permissions for head
in the Record file.Usr Grp Ohr
head
create three three-letter directories named: Usr Grp Ohr
Usr
has no permissions for group or other. The user can cd
into it, but cannot create any new content nor use ls
to see any files in it. Record the permissions.Grp
has no permissions for user or other. The group can cd
into it and use ls
in it, but cannot create any new content. Record the permissions.Ohr
has no permissions for user or group. Others have full permissions. Record the permissions.rf wf xf
Usr
create three two-letter files named: rf wf xf
rf
has read permission (only) for the user. Record the permissions.wf
has write permission (only) for the user. Record the permissions.xf
has execute permission (only) for the user. Record the permissions.rd wr xc
Grp
create three two-letter files named: rd wr xc
rd
has read and write permission (only) for the group. Record the permissions.wr
has write and execute permission (only) for the group. Record the permissions.xc
has read and execute permission (only) for the group. Record the permissions.oth *** ???
Ohr
create three three-character files named: oth *** ???
(Some characters are meta-characters that are special to the shell and will need careful handling. Review Quoting.)
oth
has full permissions for other. Record the permissions.***
has no permissions for other. Record the permissions.???
has only write permission for other. Record the permissions.Remember to Read All The Words above about working from top to bottom and then from bottom to top in this Part.
Run the Checking Program to verify your work so far.
You need to understand Permissions for this task. Do the permissions section of Worksheet #08 PDF before continuing. Record all your answers for later quizzes.
minimal.txt
Copy the file minimal.txt
from the Source Directory into your Base Directory.
Fix the permissions on the file so that only you and your group can edit it. (See the Hints about the edit verb in Part A.)
Edit the file and replace the KEY
line in the file with the output of running the program named key
located in the Source Directory. Give the program a single argument that is the file basename, i.e. minimal.txt
(To execute this program, see the Hints from Part A.)
Run the Checking Program to verify your work so far.
_
” with your answers from Worksheet #08 PDF. Missing permissions should be given as dashes so that each set of three underscores is replaced with exactly three other characters, e.g. replace ___
with -w-
not with -w
or w
.Be careful not to make other accidental changes to the file. Note the word count at the bottom of the file. Your count must match exactly, at all times. If not, re-copy the file and start over.
rwx
permissions.diff
between the original and your edited version will be helpful in knowing what you changed.Run the Checking Program to verify your work so far.
umask
to mask default permissionsIndexYou need to understand Umask for this task. Do the umask
section of Worksheet #08 PDF before continuing. Record all your answers for later quizzes.
umask.txt
Copy the file umask.txt
from the Source Directory into your Base Directory.
Fix the permissions on the file so that you can edit it and your group and others can only read it.
Edit the file and replace the KEY
line in the file with the output of running the program named key
located in the Source Directory. Give the program a single argument that is the file basename, i.e. umask.txt
Run the Checking Program to verify your work so far.
_
” with the correct three-digit umask
value that would result in each set of symbolic permissions for a new directory. (Optionally check your work by setting your umask
to the above value and then creating and examining the permissions of a new directory.)Be careful not to make other accidental changes to the file. Note the word count at the bottom of the file. Your count must match exactly, at all times. If not, re-copy the file and start over.
diff
between the original and your edited version will be helpful in knowing what you changed.umask
set incorrectly after this exercise.Run the Checking Program to verify your work so far.
That is all the tasks you need to do.
Read your CLS Linux EMail and remove any messages that may be waiting. See Reading EMail for help.
Check your work a final time using the Checking Program below and save the standard output of that program into a file as described below. Submit that file (and only that one file) to Blackboard following the directions below.
When you are done, log out of the CLS before you close your laptop or close the PuTTY window, by using the shell exit
command:
$ exit
Summary: Do some tasks, then run the Checking Program to verify your work as you go. You can run the Checking Program as often as you want. When you have the best mark, upload the single file that is the output of the Checking Program to Blackboard.
Since I also do manual marking of student assignments, your final mark may not be the same as the mark submitted using the current version of the Checking Program. I do not guarantee that any version of the Checking Program will find all the errors in your work. Complete your assignments according to the specifications, not according to the incomplete set of the mistakes detected by the Checking Program.
check
There is a Checking Program named assignment08check
in the Source Directory on the CLS. Create a symbolic link named check
in your Base Directory that links to the above Checking Program in the Source Directory, as you did in a previous assignment.
Execute the above Checking Program as a command line on the CLS. The checking program will check your work, assign you a mark, and display the output on your screen:
$ ./check | less
You may run the Checking Program as many times as you wish, allowing you to correct mistakes and get the best mark. Some task sections require you to finish the whole section before running the Checking Program at the end; you may not always be able to run the Checking Program successfully after every single task step.
When you are done with this assignment, and you like the mark displayed on your screen by the Checking Program, you must redirect only the standard output of the Checking Program into the text file assignment08.txt
in your Base Directory on the CLS, like this:
$ ./check >assignment08.txt
$ less assignment08.txt
assignment08.txt
file name.YOUR MARK for
assignment08.txt
(containing the output from the Checking Program) from the CLS to your local computer.
YOUR MARK for
assignment08.txt
file from your local computer to the correct Assignment area on Blackboard (with the exact name) before the due date:
assignment08.txt
file from your local computer. Make sure the assignment file has the correct name on your local computer before you attach it. Attach only your assignment08.txt
file for upload. Do not attach any other file names.assignment08.txt
file on the Upload Assignment page, scroll down to the bottom of the page and use the Submit button to actually upload your attached assignment08.txt
file to Blackboard.Use only Attach File, Browse My Computer on the Upload Assignment page. Do not enter any text into the Write Submission or Add Comments boxes on Blackboard; I do not read them. Use only the Attach File, Browse My Computer section followed by the Submit button. If you need to comment on any assignment submission, send me EMail.
You can revise and upload the file more than once using the Start New button on the Review Submission History page to open a new Upload Assignment page. I only look at the most recent submission.
You must upload the file with the correct name from your local computer; you cannot correct the name as you upload it to Blackboard. Make sure the file name on Blackboard is correct!
You will also see the Review Submission History page any time you already have an assignment attempt uploaded and you click on the underlined assignment08 link. You can use the Start New button on this page to re-upload your assignment as many times as you like.
You cannot delete an assignment attempt, but you can always upload a new version. I only mark the latest version.
Your instructor may also mark files in your directory in your CLS account after the due date. Leave everything there on the CLS. Do not delete any assignment work from the CLS until after the term is over!
I do not accept any assignment submissions by EMail. Use only the Blackboard Attach File, Browse My Computer. No word processor documents. Plain Text only.
Use the exact file name given above. Upload only one single file of Linux-format plain text, not HTML, not RTF, not MSWord. No fonts, no word-processing. Linux plain text only.
NO EMAIL, WORD PROCESSOR, PDF, RTF, or HTML DOCUMENTS ACCEPTED.
No marks are awarded for submitting under the wrong assignment number or for using the wrong file name. Use the exact 16-character, lower-case name given above.
WARNING: Some inattentive students don’t Read All The Words. Don’t make that mistake! Be exact.
READ ALL THE WORDS. OH PLEASE, PLEASE, PLEASE READ ALL THE WORDS!