1.1 Assignments this weekIndex

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

• Read All The Words, Do, and then Submit via Blackboard:
  • Assignment #03 HTML – working with files: PS1, find, mkdir, mv
  • Bonus (optional) Assignment #04 HTML – the VIM text editor
  • Assignment #05 HTML – using GLOB patterns and redirection
  • Really do Read All The Words. You don’t get a second chance to get it right.

1.2 Lab work this weekIndex

• Bonus (optional) Assignment #04 HTML is ready

• Assignment #05 HTML is ready

• Finish the above assignments, which involve work on the worksheets.

1.3 Upcoming testsIndex

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.

3.1 Read All The WordsIndex

• When I say “read all the words in a question, especially the Hints”
• When I say “don’t use Word to open the worksheets”
• When I say “do the worksheet to know how to do the assignment”
• When I say “keep a notebook with descriptions of each command”
• When I say “don’t work on a problem longer than 15 minutes before trying something else, such as getting help”

3.2 Useful Command to extract fields from lines: awkIndex

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 LinuxIndex

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 StackIndex

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.

4.1 Locked out of Course Linux ServerIndex

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 ServerIndex

• Count the attacks: fgrep -c "refused connect" /var/log/auth.log
• Another way to count the lines (less efficient): fgrep "refused connect" /var/log/auth.log | wc
• Only show the last 10 lines: fgrep 'refused connect' /var/log/auth.log | tail
• See the current list of evil host IPs: less /etc/hosts.evil

4.3 Job Opening in OttawaIndex

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

---

Author: 
| 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/