Updated: 2017-01-20 00:48 EST

1 Readings, Assignments, Labs, Tests, and ToDo

1.1 Read (at least) these things (All The Words)

  1. Week 03 Notes HTML – this file – Read All The Words
  2. 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. List of Commands You Should Know
  7. Linux and Sysadmin News in the World

1.2 Assignments this week

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

1.3 Lab work this week

1.3.1 Worksheets

Worksheets are preparation for your assignments. You can’t do the assignments without having done the worksheets first, and you can’t do the worksheets without having first read the Course Notes: 1. Read. 2. Worksheet. 3. Assignment.

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 are not for hand-in; they are not worth marks; the assignments test your knowledge of the lectures and 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 Worksheet 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.

These first two worksheets require you to have read File System and Pathnames:

Worksheets prepare you for the upcoming assignments.

2 Notes from the Classroom

An Update Is Available

An Update Is Available

2.1 Did not change password – CLS access revoked

Students will have their CLS accounts disabled if they have not changed their default password. (I do not want people breaking into my machine because of you.)

See my online timetable for how to make an office appointment to see me if you want your account back.

2.2 Fifteen minute rule

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!

2.3 Drawing File System Diagrams

See the note in Assignment #03 HTML about drawing file system diagrams on paper. Do it.

2.4 Commands Used

Keep a notebook with a List of Commands in it. - You need to write down yourself what each command does. - I will check for this list in your lab periods. - Check the updated list of commands each week.

3 Attacks on the CLS

Commands to show the 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.)

4 Locked out of the CLS

When you are locked out, follow the directions in the notes to get your IP address re-enabled.

Take Notes in Class

Take Notes in Class

Author: 
| Ian! D. Allen, BA, MMath  -  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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