Updated: 2015-10-14 16:47 EDT

1 Readings, Assignments, Labs, Tests, and ToDoIndexup to index

1.1 Read (at least) these things (All The Words)Indexup to index

  1. Week 03 Notes HTML – this file – Read All The Words
  2. Unix/Linux File System and Pathnames (ROOT, absolute, relative, dot, dot dot
  3. Directories: ROOT, /root, HOME, /home, and current
  4. Searching for and finding files by name, size, use, modify time, etc.
  5. Shell GLOB patterns (wildcard pathname matching)
  6. The VI (VIM) Text Editor
  7. List of Commands You Should Know
  8. Linux and Sysadmin News in the World

1.2 Assignments this weekIndexup to index

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

1.2.1 WorksheetsIndexup to index

Form a small study group to do the worksheets. Each person tries the example given, and you make sure you all get the same answers. Worksheets teach you how commands work. Worksheets are not for hand-in; they are not worth marks.

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.

1.3 Lab work this weekIndexup to index

1.4 Upcoming testsIndexup to index

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

  1. First Midterm test: 45 minutes; in lecture class Friday in Week 5 (Oct 9)
  2. Second Midterm test: 45 minutes; in lecture class Friday in Week 9 (Nov 6)

Tests take place in class in your one-hour lecture hour, not in your lab period.

1.4.1 Midterm Test #1 – October 9Indexup to index

  • Midterm #1 takes place on Friday, October 9 (Week 5) 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.
  • I will post a set of practice questions and quizzes for the test soon.

3 From the Classroom Whiteboard/ChalkboardIndexup to index

3.1 Disabled SFTP writing on CLSIndexup to index

To improve CLS security, I’ve disabled the writing or changing of files on the CLS by the SFTP service, as used by file transfer programs such as WinSCP and FileZilla. You can copy files out of the CLS (e.g. your assignments) using WinSCP and friends, but you can’t copy files into the CLS unless you use the secure scp program.

3.2 Fifteen minute ruleIndexup to index

Your time as a student is valuable. If you come up against a tough problem and make no progress in fifteen minutes despite best efforts:

  1. get help from a professor or lab instructor
  2. get help from classmates
  3. take a break
  4. put it on hold and work on something else

This happens to all of us, and we need to watch out for it when it happens.

But what about when it’s midnight before the assignment is due?

Remember the “Don’t Leave Things to the Last Minute” rule!

 Take Notes in Class

3.3 CommandsIndexup to index

4 Attacks on the CLSIndexup to index

Number of locked out IP addresses and attempts to use locked-out IP addresses in /etc/hosts.evil:

$ wc /etc/hosts.evil
$ fgrep -c 'refused' /var/log/auth.log
$ fgrep 'refused' /var/log/auth.log | less

Count the unique locked-out addresses and show the top twenty:

$ fgrep 'refused' /var/log/auth.log | awk '{print $NF}' | sort -u | wc
$ fgrep 'refused' /var/log/auth.log | awk '{print $NF}' \
    | sort | uniq -c | sort -nr | head -n 20

Password failures:

$ fgrep -c 'Failed' /var/log/auth.log
$ fgrep 'Failed' /var/log/auth.log | less

Userid failures:

$ fgrep -c 'input_userauth' /var/log/auth.log
$ fgrep 'input_userauth' /var/log/auth.log | less

You can use the whois command on Linux to identify which country is responsible for an IP address, or use a Web Whois Lookup. (The Linux whois command is blocked from use at Algonquin College, except if you are on the CLS. You can’t use the Linux command in your own Linux machines on campus. Use it on the CLS or use the web interface instead.)

5 Locked out of the CLSIndexup to index

I told you not to use a blank userid in the file transfer program:

Sep 19 17:05:04 Invalid user  from
Sep 19 17:05:18 Failed password for invalid user  from
Sep 19 17:05:41 Failed password for invalid user  from
Sep 19 17:05:49 Connection closed by
Sep 19 17:06:01 Invalid user  from
Sep 19 17:06:24 Failed password for invalid user  from
Sep 19 17:06:42 Failed password for invalid user  from
Sep 19 17:06:46 Connection closed by
Sep 19 17:07:28 refused connect from cpe00fc8d413af3-cm00fc8d413af0.cpe.net.cable.rogers.com (
Sep 19 17:07:58 refused connect from cpe00fc8d413af3-cm00fc8d413af0.cpe.net.cable.rogers.com (


| Ian! D. Allen  -  idallen@idallen.ca  -  Ottawa, Ontario, Canada
| Home Page: http://idallen.com/   Contact Improv: http://contactimprov.ca/
| College professor (Free/Libre GNU+Linux) at: http://teaching.idallen.com/
| Defend digital freedom:  http://eff.org/  and have fun:  http://fools.ca/

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