Updated: 2015-10-01 03:54 EDT

1 Readings, Assignments, Labs, Tests, and ToDo

1.1 Assignments this week

Check the due date for each assignment and put a reminder in your agenda, calendar, and digital assistant.

1.1.1 Worksheets

The worksheets are available in four formats: Open Office (ODT), PDF, HTML, and Text. Only the Open Office format allows you “fill in the blanks” in the worksheet. The PDF format looks good but doesn’t allow you to type into the blanks in the worksheet. The HTML format is crude but useful for quick for viewing online.

Do NOT open the ODT files using any Microsoft products; they will mangle the format and mis-number the questions. Use the free Libre Office or Open Office programs to open these ODT documents. On campus, you can download Libre Office here.

1.2 Lab work this week

1.3 Upcoming tests

Read the Test Instructions (all the words) before your first midterm test.

  1. First Midterm test: 45 minutes; in class 8am Thursday in Week 6 (February 12)
  2. Second Midterm test: 45 minutes; in class 8am Thursday in Week 9 (March 12)

Tests take place in your 8am lecture hour, not in your lab period.

1.3.1 Midterm Test #1

  • Midterm #1 takes place 8am Thursday February 12 (Week 6) in your scheduled lecture hour (not in your lab period).
  • For full marks, you must read the Test Instructions before the test for important directions on how to enter your answers, your lab (not lecture) section number, and the test version number on the question sheet and the mark-sense forms.
  • There may be more questions on the test than you can answer in the time allowed; answer the ones you know, first.
  • A set of practice questions and answers for the first midterm test is posted: Practice Tests and Answers.
  • Blackboard has some quizzes taken randomly from the practice test. See below.

1.3.2 Quizzes: Midterm #1 Quiz

This quiz is one of several quizzes in this course. Each midterm and final exam will have an associated quiz. See the course outline for the mark weight of all course quizzes, midterm tests, and exams.

The quizzes are open-book, but the midterm tests and final exam are closed-book.

This quiz is based on the Midterm #1 Practice Test questions that are posted in the Class Notes. The quiz is 10 questions long and you see the answers right after you submit the quiz. You can take the quiz as many times as you like. Every time you take the quiz, you get a random set of ten questions from the practice test. You will not see all the practice questions by doing quizzes; to see all the practice questions, you must do all the questions in the actual PDF practice test posted in the Course Notes.

This quiz closes just before the Final Exam in this course; quizzes submitted after the Final Exam begins may not count toward your best score.

Your mark for this quiz is the average of your five best quiz scores. Examples:

  • Your best scores: 10 10 10 10 10 10 10 9 8 7 7 4
    • Your quiz mark: (10+10+10+10+10)/50 = 100%
  • Your best scores: 10 10 10 10 9 8 7 7 4 3
    • Your quiz mark: (10+10+10+10+9)/50 = 98%
  • Your best scores: 10 10 10 9 8 7 7 4 3 2
    • Your quiz mark: (10+10+10+9+8)/50 = 94%
  • Your best scores: 10 8 8 8 8 5 4 4 4
    • Your quiz mark: (10+8+8+8+8)/50 = 84%
  • Your best scores: 10 10 8 (only three quizzes submitted)
    • Your quiz mark: (10+10+8+0+0)/50 = 56%

Your score will be taken from the five best scores. The more times you do the quiz, the more likely you are to have a set of excellent best scores. You must have five perfect quiz scores to get a perfect averaged quiz mark. Missing quizzes (fewer than five) count as zeroes. Only the five best scores are averaged. (Blackboard averages all the scores and thus displays your score incorrectly.)

This quiz closes just before the Final Exam in this course; quizzes submitted after the Final Exam begins may not count toward your best score.

See the Assignments and Quizzes section in the Blackboard left side-bar for your course.

Note: Blackboard displays the quiz mark incorrectly, since it cannot calculate “best 5” and instead averages the marks ofall* your quiz attempts. Your quiz mark is actually the average of your five best attempts, not all the attempts as shown by Blackboard. Ignore the Blackboard mark; it is wrong.*

3 From the Classroom Whiteboard/Chalkboard

3.1 Read All The Words

3.2 Useful Command to extract fields from lines: awk

The oddly-named awk command can extract a field, by field number, from one or more input lines. The default is to find fields separated by any amount of space characters:

$ echo one two three four five
one two three four five
$ echo one two three four five | awk '{ print $1 }'
one
$ echo one two three four five | awk '{ print $2 }'
two
$ echo one two three four five | awk '{ print $5 }'
five

You can also use the field number NF (Number of Fields) to extract just the last field from any input lines:

$ echo one two three four five | awk '{ print $NF }'
five
$ echo one two three four | awk '{ print $NF }'
four
$ echo one two three | awk '{ print $NF }'
three
$ echo one two | awk '{ print $NF }'
two
$ echo one | awk '{ print $NF }'
one

The single command-line argument to awk must be single-quoted to hide the dollar character from the shell.

Here is a common use of fgrep to select lines and awk to extract fields from a system log file and count the unique occurrences:

$ fgrep 'refused connect' /var/log/auth.log \
   | awk '{print $NF}' \
   | sort | uniq -c | sort -nr | head

3.3 Working Smart under Linux

Growing up under Mac/Windows, you are accustomed to having to “go to” a folder to make any changes to files in that folder. This leads to some inefficient behaviour under Unix/Linux, because Unix/Linux can operate on any file in any folder without having to “go” there:

The “Windows/Mac” way to create a file under a/b/c/d/date.txt:

$ mkdir a
$ cd a
$ mkdir b
$ cd b
$ mkdir c
$ cd c
$ mkdir d
$ cd d
$ date >date.txt
$ cd

The Unix/Linux way:

$ mkdir -p a/b/c/d
$ date >a/b/c/d/date.txt

The “Windows/Mac” way to rename a file under a/b/c/d/date.txt to be old.txt:

$ cd a
$ cd b
$ cd c
$ cd d
$ mv date.txt old.txt
$ cd

The Unix/Linux way:

$ mv a/b/c/d/date.txt a/b/c/d/old.txt

The “Windows/Mac” way to delete a/b/c/d/old.txt:

$ cd a
$ cd b
$ cd c
$ cd d
$ rm old.txt
$ cd

The Unix/Linux way:

$ rm a/b/c/d/old.txt

Using Unix/Linux pathnames, you can work faster, and all your commands are saved in your history for modification and re-use.

3.4 Current Working Directory Stack

The shell built-in command pushd works like cd to change the current directory, but it saves the previous directory on a stack and lets you type popd to return to the previous directory. You may find this saves you some typing. See the shell man page or use the help built-in.

4 Real Sysadmin Work

4.1 Locked out of Course Linux Server

I told you not to try to log in to the CLS with a blank userid. Now your home IP address is locked out from the CLS:

Jan 30 14:25:52 Accepted password for XXXXXXXX from 74.14.198.226
Jan 30 17:35:15 Invalid user  from 74.14.198.226
Jan 30 17:35:30 Failed password for invalid user  from 74.14.198.226
Jan 30 17:35:59 Failed password for invalid user  from 74.14.198.226
Jan 30 17:36:07 Failed password for invalid user  from 74.14.198.226
Jan 30 17:37:25 Invalid user  from 74.14.198.226
Jan 30 17:38:01 Invalid user  from 74.14.198.226
Jan 30 17:38:30 Failed password for invalid user  from 74.14.198.226
Jan 30 17:39:03 Failed password for invalid user  from 74.14.198.226
Jan 30 17:41:51 refused connect from bas16-ottawa23-1242482402.dsl.bell.ca (74.14.198.226)
Jan 30 17:43:03 refused connect from bas16-ottawa23-1242482402.dsl.bell.ca (74.14.198.226)

Someone else did the same thing, and also got locked out:

Feb  1 00:10:21  Accepted password for XXXXXXXX from 23.91.145.228
Feb  1 05:58:08 Invalid user  from 23.91.145.228
Feb  1 05:58:31 Failed password for invalid user  from 23.91.145.228
Feb  1 05:58:59 Failed password for invalid user  from 23.91.145.228
Feb  1 05:59:21 Failed password for invalid user  from 23.91.145.228
Feb  1 06:01:12 Invalid user  from 23.91.145.228
Feb  1 06:01:51 Failed none for invalid user  from 23.91.145.228
Added the following hosts to /etc/hosts.evil: 23-91-145-228.cpe.pppoe.ca

Someone spelled their own userid incorrectly (seven characters) over and over, and got locked out:

Jan 26 00:11:25 Accepted password for XXXXXXXX from 76.69.121.114
Feb  1 09:21:04 Invalid user XXXXXXX from 76.69.121.114
Feb  1 09:21:25 Failed password for invalid user XXXXXXX from 76.69.121.114
Feb  1 09:21:50 Failed password for invalid user XXXXXXX from 76.69.121.114
Feb  1 09:22:10 Failed password for invalid user XXXXXXX from 76.69.121.114
Feb  1 09:22:30 Failed password for invalid user XXXXXXX from 76.69.121.114
Added the following hosts to /etc/hosts.evil: otwaon0916w-lp140-02-1279621490.dsl.bell.ca

Don’t do that.

4.2 Attacks on the Course Linux Server

4.3 Job Opening in Ottawa

From the local linux-consult mailing list:

From: "David F. Skoll" <dfs@roaringpenguin.com>
To: linux-consult@list.flora.ca
Date: Wed, 7 Jan 2015 14:51:49 -0500
Organization: Roaring Penguin Software Inc.
Subject: [Linux-consult] Term position for technical support specialist at Roaring Penguin

Please see below for an opening at Roaring Penguin.  If you're
interested in applying, please send your cover letter and resume
(plain-text, HTML or PDF only, please) to jobs@roaringpenguin.com

Info about our company is at https://www.roaringpenguin.com/company

Regards,

David.

==========================================================================
Roaring Penguin Software seeks a Technical Support Specialist to
provide customer support for its anti-spam products and services.
This position is a full-time term position for six months.  Depending
on circumstances, it is possible that the position will become a
permanent position.

Requirements for the position are:

o Extensive familiarity with Linux system administration.  Familiarity
  with the Debian or Debian-derived distributions would be an asset.

o Extensive familiarity with SMTP and related email standards such
  as DKIM, SPF, DMARC and MIME.

o Understanding of the TCP/IP suite and related protocols including DNS.

o A pleasant, efficient phone manner and excellent English verbal and
  written communication skills.

o The willingness to be on-call for remote support between 9am and 9pm
  for one week out of four.

The following are not requirements, but are highly desirable:

o Experience in a technical support role.
o Familiarity with Perl and PHP.
o Familiarity with the PostgreSQL database system.
o Familiarity with the Sendmail MTA.
_______________________________________________
Linux-consult mailing list
Linux-consult@list.flora.ca
http://list.flora.ca/mailman/listinfo/linux-consult

Take Notes in Class

Take Notes in Class

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