Updated: 2015-03-30 11:06 EDT

1 Due Date and Deliverables

Do not print this assignment on paper!

WARNING: Some inattentive students upload Assignment #11 into the Assignment #10 upload area. Don’t make that mistake! Be exact.

2 Purpose of this Assignment

Do not print this assignment on paper! On paper, you cannot follow any of the hyperlink URLs that lead you to hints and course notes relevant to answering a question.

This assignment is based on your weekly Class Notes.

  1. Working with tar archives from Package Management
  2. Working with Processes and Jobs
  3. Working with System Log Files
  4. Using the Crontab and At Job Schedulers (cron and at)
  5. Sending EMail and Reading EMail on the CLS.

Remember to READ ALL THE WORDS to work effectively and not waste time.

3 Introduction and Overview

This is an overview of how you are expected to complete this assignment. Read all the words before you start working.

For full marks, follow these directions exactly.

  1. Complete the Tasks listed below, in order, and don’t skip steps.
  2. Verify your own work before running the Checking Program.
  3. Run the Checking Program at the end of the task to help you find errors.
  4. Submit the output of the Checking Program to Blackboard before the due date, following the directions given below.
  5. READ ALL THE WORDS to work effectively and not waste time.

3.1 Notes on checking your work

  1. 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. 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!
  2. 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.
  3. You can modify your work and check it with the Checking Program as often as you like before you submit your final mark. You can submit your mark as many times as you like before the due date.

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.

3.2 The Source Directory

All references to the Source Directory below are to the CLS directory ~idallen/cst8207/15w/assignment11/ 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.

3.3 Searching the course notes on the CLS

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.

4 Tasks

4.1 Set Up – The Base Directory on the CLS

You must keep a list of command names used each week and write down what each command does, as described in the List of Commands You Should Know. Without that list to remind you what command names to use, you will find assignments very difficult.

  1. Do a Remote Login to the Course Linux Server (CLS) from any existing computer, using the host name appropriate for whether you are on-campus or off-campus.

  2. Make the CLS directory ~/CST8207-15W/Assignments/assignment11 in which you will create the files and scripts resulting from the following tasks.

  3. Create the check symbolic link needed to run the Checking Program, as described in the section Checking Program below.

This assignment11 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.

4.2 Part A – Disk Usage, tar Archive and Listing

You need to know Disk Usage and Package Management to do this task.

  1. Make your Base Directory your current directory and do not change directories for this task. All recorded pathnames must be relative to the Base Directory.

abcd0001

  1. In the current directory (the Base Directory), create a directory named 3maze. Without changing directories, create a symbolic link in that 3maze directory that is the name of your 8-character CLS userid. The symlink should point to the absolute path of the maze directory that is in the Assignment #03 Source Directory. The symbolic link will have a size of exactly 43 characters (the absolute path of the maze directory), e.g. for userid abcd0001 the symlink long listing would start like this:

    lrwxrwxrwx 1 abcd0001 abcd0001 43 Mar 22 12:03 3maze/abcd0001 -> 

    The rest of the symlink is the absolute path of the maze directory.

    You probably have it right if ls 3maze/abcd0001 shows about 1700 (non-hidden) pathnames from the maze.

  2. Display the sum total of disk blocks in the hidden 3maze/abcd0001/.0 sub-directory inside the maze.
    • Use your own userid, not abcd0001
    • The number printed should be larger than 6100.
    • The relative pathname beside the number should be exactly as given.
    • You will need this exact relative pathname in the next questions.

mazeblocks.txt

  1. Put the above one-line of output (the number of disk blocks) into a new file mazeblocks.txt in the 3maze directory.
    • The file will be one line long, containing two words: a number larger than 6100 and a relative pathname containing two slashes.

YYYYMMDD.tar.gz

  1. Create a gzip-style compressed tar archive in the 3maze directory containing the contents of the .0 directory from above. Use the relative pathname from above as the source of the files to archive. Name the new archive YYYYMMDD.tar.gz (no spaces) under 3maze, where YYYYMMDD is the numeric year-month-day date of the final exam in this course.
    • The gzip-style compressed archive will be approximately 20000 bytes.
    • All the pathnames in the tar archive file must be relative paths with 3maze/abcd0001/.0/ at the beginning of every name.

YYYYMMDD.tar.bz2

  1. Create a bzip2-style compressed tar archive in the 3maze directory of the same .0 directory from above. Use the same name as for the gzip archive, but use the file extension .bz2 instead of the .gz extension.
    • The bzip2-style compressed archive will be approximately 6600 bytes.
  2. Look up the option to ls that gives “the allocated size of each file, in blocks” and use that option (and only that option) to display the size and name of the two tar archives you just created in the 3maze directory.
    • The output will be one line long, four words, with each tar archive name preceded by its size in blocks.
    • A GLOB pattern will be helpful to generate the two archive pathnames in the 3maze directory.

mazeblocks.txt

  1. Append the output of the above command line (the sizes and relative pathnames) to the disk blocks file you created earlier. The file will now be three lines (six words) long.
    • Note how the output of ls changes to separate lines when output is to a file instead of directly to your screen. This is one of the few commands that does this.
    • Look at the three lines in the disk blocks file and note how the compressed tar archives are much smaller (fewer disk blocks) than the original disk space used.
    • Note how the newer bzip2 compression algorithm is much better at compressing this file (fewer disk blocks) than the older gzip algorithm.
    Hint: Go back and re-read the first step in this task if you don’t have the right pathnames in your output.

tar_tvzf.txt

  1. Generate a verbose listing of your gzip-style tar archive file, showing the contents of the archive including all the owners and date/time stamps, but don’t display it directly on your screen since it’s over 1,500 lines long. Save just the first five and last five lines of the verbose listing into file tar_tvzf.txt under 3maze directory. The file word count will be 10 60 751 and the first line and last line should look like this (where abcd0001 is replaced by your userid):

    drwxr-xr-x idallen/idallen   0 2012-02-13 13:33 3maze/abcd0001/.0/
    drwxr-xr-x idallen/idallen   0 2012-02-13 13:33 3maze/abcd0001/.0/.1/.1/.1/

    Hint: You will need to use one command pipeline to generate the first five lines into the output file, and a second command pipeline to generate the last five lines and append them to the output file to make a total of ten lines in the file.

  2. The bzip2 compression algorithm is better than the gzip compression algorithm; bzip2 produces smaller compressed files. Answer this question:

    True or False: Because bzip2 is smaller than gzip, generating the verbose table of contents of the bzip2-style tar archive file will produce fewer lines than the table of contents of the gzip-style archive. Append your one-word answer true or false to the tar_tvzf.txt file. (The file will now contain 11 lines.) (The checking program will not check this answer. Your instructor will check the answer and mark it after you hand in your assignment.)

Run the Checking Program on the CLS to verify your work so far.

If you have errors, go back and re-read the first step in this task.

4.3 Part B – Process Listing

You need to know Processes and Jobs to do this task.

psbsd.txt

  1. Place a full list of all processes for all users, BSD format, all users, text user name (not numeric UID), full wide listing (not truncated at all), into file psbsd.txt in your Base Directory. It should be at least 105 lines and 9KB. The header line and one of the very long lines will be a dhclient line similar to this (use a text-searching command to find it in the output):

    USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
    root      4078  0.0  0.0   7264   388 ?        Ss   Mar15   0:00 dhclient3 -e IF_METRIC=9999 -pf /var/run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -1 eth0

psunix.txt

  1. Place a full list of all processes for all users, UNIX (System V) format, text user name (not numeric UID), full wide listing (not truncated at all), into file psunix.txt in your Base Directory. It should be at least 105 lines and 7KB. The header line and one of the very long lines will be a dhclient line similar to this (use a text-searching command to find it in the output):

    UID        PID  PPID  C STIME TTY          TIME CMD
    root      4078     1  0 Mar15 ?        00:00:00 dhclient3 -e IF_METRIC=9999 -pf /var/run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -1 eth0

mine.txt

  1. Pick off the first line (the header line) of the psbsd.txt file and put the one line into file mine.txt. (1 11 73 mine.txt)
    • There is a command that can do this easily.
    • Make sure you pick the header line from the right file.
  2. Find all lines in psbsd.txt that contain your userid anywhere in the line and append those lines to the mine.txt file. (Some of the lines in this file may be very long.)

4.3.1 Hiding command names: vi thesis

You need to know about Job Control and Background Processes to do this section.

We will now create a symbolic link named vi thesis that will run a command that has a different name. The ps command will show the vi thesis name of the symlink, not the name of the program that is the target actually being run. Users or attackers may use this symlink trick to hide the actual name of a command that they are using.

vi thesis

  1. Create a symbolic link named vi thesis in your Base Directory that points to (has as a target) the absolute pathname of the system sleep command.
    • Hints: You need to find which absolute pathname the shell uses to run the sleep command name. See “Commands related to PATH” in Search Path. You need to remember how to create a Symbolic Link.
  2. Confirm that your symlink is working by running a checksum on the vi thesis name and making sure it prints the same checksum number as a checksum of the real sleep program file.
    • If you see vi thesis: No such file or directory, you didn’t get the symbolic link correct.
    • If you see vi: No such file or directory, you forgot to hide the blank in the name from the shell. See Quoting.
  3. Run your new vi thesis command (that name is in the current directory) as a background job with a single argument of 999 (that the command will interpret as a number of seconds to sleep). Your shell will print a shell background job number and process ID similar to: [1] 12345

    Hints: You need to remember how to execute a command in the current directory, and how to run a job in the background. You need to know how to hide blanks (in the command name) from the shell. If you got the symlink correct, you can use the TAB key to ask the shell to complete the command name in the current directory. You do not need any “seconds” qualifier on the 999 number; the number defaults to seconds. If you create more than one background job, the job number will be bigger than [1].

thesis.txt

  1. Confirm that your vi thesis command is running by asking the shell for a listing of jobs of the shell that includes the process ID of the jobs. It will look similar to this (note the process ID is included by using an option):

    [1]+ 12345 Running                 ./vi\ thesis 999 &

    Redirect the above output (showing the PID number) into file thesis.txt in your Base Directory. If you have more than one background job, the job numbers will be bigger than [1].

  2. Run the ps command and you should see output similar to this:

      PID TTY          TIME CMD
    12345 pts/5    00:00:00 vi thesis
    15000 pts/5    00:00:00 ps
    22460 pts/5    00:00:00 bash

    Note the vi thesis command, which is really sleep, and could be made to be any command you like if you change the symlink target. (The command name shown by ps is not necessarily accurate.)

  3. Append the above ps output to your thesis.txt file. The file will have at least five lines in it.

  4. Kill the job, using the special shell syntax for its job number. When you next push the [Enter] key, you should see: [1]+ Terminated ./vi\ thesis 999 If you have more than one background job, the job numbers will be bigger than [1].

Run the Checking Program on the CLS to verify your work so far.

4.4 Part C – System Log Files

You need to know System Log Files to do this task.

syslog.txt

  1. What is the actual name of the syslog program on the CLS? Search for and extract the one line from each file psbsd.txt and psunix.txt that contains this name and redirect the results (two lines, one from each file) into file syslog.txt. (The result will be 2 lines, 21 words.)

authlog.txt

  1. The system authentication log file is named auth.log in the system log directory. Generate an ls long listing showing inode number of this file using the full absolute pathname, and put the results of the ls (the output of ls) into file authlog.txt. (The result of the ls command should be 1 line, 9 words, at least 60 characters.)

    (Optional: You may find it convenient to set a shell variable to this absolute pathname, so that you can use the short variable name rather than the long absolute pathname in the rest of these exercises. Or, you could make a short symbolic link to this file.)

id.txt

  1. Use one command name to put a list (one line) of your numeric UID, your userid, your numeric GID, your group name, and your additional group names into the file id.txt. The result will be 1 (long) line, 3 words. See Permissions for the command to use to do this. Do not edit the output of the command.

myperms.txt

  1. Look at the contents of the id.txt and authlog.txt files. Note that your account is in a group that matches the group of the system auth.log file, giving you group permissions on this file. Using a text editor, put the matching group name, the symbolic group permissions (three characters), and the octal group permissions (one digit), onto three lines in file myperms.txt. (The result will be 3 lines, 3 words, 10 characters. Do you remember why a file containing seven alphanumeric characters on three lines is counted as a 10-character file on Linux? Review Line End Differences.)

authhead.txt

  1. The system auth.log file contains (March 2015) over 2,222,310 lines. Use a command to extract just the first line (one line) from the head of this file and redirect that one line into new file authhead.txt. (The result will be 1 line 14 words 111 chars.) The time and date at the start of this line is when this copy of the log file was started.

failedpass.txt

  1. If you count the number of lines in the system auth.log containing the exact text string Failed password, the count is more than 7,820 lines (March 2015). Of those lines (the lines containing that exact text string), extract just lines 100 through 110 (inclusive) and put only those lines into file failedpass.txt. The word count for the file will be 11 174 1279. Every line should contain the exact text string somewhere.

Run the Checking Program on the CLS to verify your work so far.

4.5 Part D – Crontab

You need to know Crontab and At Job Schedulers to do this task. Re-read the Notes on checking your work before you continue.

crontab.txt

  1. Create a personal crontab entry that uses a command to update the (access and) modification time on file crontab.txt in your Base Directory (not in your HOME directory) every minute of every day. Use the shortest relative pathname to your crontab.txt file. Do not use an absolute pathname. Verify that the time of the file changes every minute.

    Hints: If it doesn’t work, read your Linux EMail for EMail messages from the Cron daemon showing possible errors. See Reading EMail for help. The single working crontab line should be seven words: five for the date/time, a command name, and a relative file name.

crontab1.txt

  1. List your personal crontab (one entry, with perhaps some comment lines) and redirect the output into file crontab1.txt in your Base Directory. This entry should run every minute.

  2. Delete your personal crontab (the one that runs every minute).

crontab.txt

  1. Create a personal crontab entry that redirects the current date and time into the same file crontab.txt at The Crontab Time. Also use a relative pathname, not an absolute pathname.

crontab2.txt

  1. List your personal crontab (one entry, with perhaps some comment lines) and redirect the output into file crontab2.txt. Do not delete this personal crontab entry; leave it for marking. Make sure your displayed cron job is scheduled at The Crontab Time.

Run the Checking Program on the CLS to verify your work so far.

Re-read the Notes on checking your work if you are trying to check your work in the middle of a task instead of at the end of a task.

4.6 Part E – At Job Reminder

You need to know Crontab and At Job Schedulers to do this task.

  1. Create an at job that prints the list of users on the system, one per line, at The Crontab Time in the year 2016. You can use any of several commands to show the list of users one per line; see the List of Commands You Should Know.

    Hints: You need to get the order of the date correct on the at command line; see the Crontab and At Job Schedulers course notes or RTFM to find out how to specify both a time and a date for an at job. No pipes are needed for this at job; it’s just one command name.

  2. Display your list of at jobs to confirm the correct scheduling date and time in 2016.

  3. Create an at job that runs the command that prints the name of this computer at The Crontab Time in the year 2016.

    Hints: You used this same command name in an assigment shell script recently.

  4. Create an at job that echoes the one line of text Exam 11am Today to your Algonquin Live EMail account at 1 AM on the date of your final exam in this course. The EMail message sent at 1am must have the exact three-word echo text and exact five-word subject: CST8207 Final Exam 11AM Today

    Hints: A pipe will be needed to connect the one-line output of echo with the standard input of the mail program. See Sending EMail for help in sending EMail with a subject line. Did you use the exact words given to you for the echo and Subject texts?

  5. Check the queue of at jobs and make sure the scheduled times are correct.

  6. Delete the at job that shows the list of users.

atjob.txt

  1. Display both your queued at jobs and redirect the output into file atjob.txt. You will only have two jobs – two lines. If you have more than two lines, delete the other jobs.

  2. Leave these two jobs queued on the CLS for marking.

Run the Checking Program on the CLS to verify your work so far.

4.7 When you are done

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

5 Checking, Marking, and Submitting your Work

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.

  1. There is a Checking Program named assignment11check in the Source Directory on the CLS. You can execute this program by typing its (long) pathname into the shell as a command name:

    $ ~idallen/cst8207/15w/assignment11/assignment11check

    You learn one way to make this shorter in the current assignment.

  2. Execute the above Checking Program as a command line on the CLS. This program will check your work, assign you a mark, and display the output on your screen.

    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.

  3. 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 assignment11.txt in your Base Directory on the CLS, like this:

    $ ~idallen/cst8207/15w/assignment11/assignment11check >assignment11.txt
    $ cat assignment11.txt
    • Use output redirection with that exact assignment11.txt file name.
    • Use that exact name. Case (upper/lower case letters) matters.
    • Be absolutely accurate, as if your marks depended on it.
    • Do not edit the output file.
    • Make sure the file actually contains the output of the Checking Program!
    • The file should contain, near the bottom, a line starting with: YOUR MARK for
    • Really! MAKE SURE THE FILE HAS YOUR MARKS IN IT!
  4. Transfer the above single file assignment11.txt (containing the output from the Checking Program) from the CLS to your local computer.
    • You may want to refer to the File Transfer page for how to transfer the file.
    • Verify that the file still contains all the output from the Checking Program.
    • Do not edit this file! No empty files, please! Edited or damaged files will not be marked. Submit the file exactly as given.
    • The file should contain, near the bottom, a line starting with: YOUR MARK for
    • Really! MAKE SURE THE FILE YOU UPLOAD HAS YOUR MARKS IN IT!
  5. Upload the assignment11.txt file from your local computer to the correct Assignment area on Blackboard (with the exact name) before the due date:
    1. On your local computer use a web browser to log in to Blackboard and go to the Blackboard page for this course.
    2. Go to the Blackboard Assignments area for the course, in the left side-bar menu, and find the current assignment.
    3. Under Assignments, click on the underlined assignment11 link for this assignment.
      1. If this is your first upload, the Upload Assignment page will open directly; skip the next sentence.
      2. If you have already uploaded previously, the Review Submission History page will be open and you must use the Start New button at the bottom of the page to get to the Upload Assignment page.
    4. On the Upload Assignment page, scroll down and beside Attach File use Browse My Computer to find and attach your assignment file from your local computer. Make sure the assignment file has the correct name on your local computer before you attach it.
    5. After you have attached the file on the Upload Assignment page, scroll down to the bottom of the page and use the Submit button to actually upload your attached assignment file to Blackboard.

    Use only Attach File on the Upload Assignment page. Do not enter any text into the Text Submission or Comments boxes on Blackboard; I do not read them. Use only the Attach File 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.

  6. Verify that Blackboard has received your submission: After using the Submit button, you will see a page titled Review Submission History that will show all your uploaded submissions for this assignment. Each of your submissions is called an Attempt on this page. A drop-down list of all your attempts is available.
    1. Verify that your latest Attempt has the correct 16-character, lower-case file name under the SUBMISSION heading.
    2. The one file name must be the only thing under the SUBMISSION heading. Only the one file name is allowed.
    3. No COMMENTS heading should be visible on the page. Do not enter any comments when you upload an assignment.
    4. Save a screen capture of the Review Submission History page on your local computer, showing the single uploaded file name listed under SUBMISSION. If you want to claim that you uploaded the file and Blackboard lost it, you will need this screen capture to prove that you actually uploaded the file. (To date, Blackboard has never lost an uploaded file.)

    You will also see the Review Submission History page any time you already have an assignment attempt uploaded and you click on the underlined assignment11 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.

  7. 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!

READ ALL THE WORDS. OH PLEASE, PLEASE, PLEASE READ ALL THE WORDS!

6 Appendix I: The Crontab Time

This section shows you how to calculate your personal Crontab Time for use in your cron and at jobs. You need to know your nine-digit student number and how to calculate the arithmetic modulus of a number.

  1. Take your 9-digit student number and remove the first three digits (probably 040), leaving six digits. Use these last six digits as follows:
  2. Take the first two of those six digits as a number, modulo 12, and then add 1, giving a number between 1 and 12. This is your month number.
  3. Take the next (middle) two of those six digits as a number, modulo 24, giving a number between 0 and 23. This is your hour number.
  4. Take the last two of those six digits as a number, modulo 60, giving a number between 0 and 59. This is your minute number.
  5. Take the same last two of those six digits as a number, modulo 28, and then add 1, giving a number between 1 and 28. This is your day-of-the-month number.

For example, if your nine-digit student number were 123456789:

  1. Remove the first three digits 123, leaving the last six digits 45 67 89
  2. Using the first two digits 45, the month would be (45 mod 12) + 1 = 10 (October)
  3. Using the next two digits 67, the hour would be 67 mod 24 = 19 (7pm)
  4. Using the last two digits 89, the minute would be 89 mod 60 = 29
  5. Using the last two digits 89, the day of the month would be (89 mod 28) + 1 = 6

The Crontab Time for student number 123456789 is October 6 at 19h29 (7:29pm).

Exercise: Show that The Crontab Time for student number 987654321 is

  1. last six digits = 65 43 21
  2. month = 6 (June)
  3. hour = 19 (7pm)
  4. minute = 21
  5. day of month = 22

which is June 22 at 19h21 (7:21pm).

Author: 
| Ian! D. Allen  -  idallen@idallen.ca  -  Ottawa, Ontario, Canada
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