IT 244: Introduction to Linux/Unix
Class 2
Today's Topics
New Material
Reading Assignment
Reading assignment for this week is chapter 1 of Sobell,
Welcome to Linux and Mac OS X
You need read this before next week's class.
All reading assignments are posted at
http://www.cs.umb.edu/~tsoro/teaching/it244_html/readings_it244.html
Homework 1
Remember, homework 1 is due this Sunday by 11:59 PM.
You will find it here.
There are three parts to this assignment
- An email containing answers to questions on the assignment
- Registering with class discussion area for this course on Piazza
- Forwarding you UMB email to an email account you check frequently
You must forward your UMB email since I will use that address to send
you your scoring sheets for assignments.
I will also use this address to send you news of any changes in assignments or
other developments
I will check that the forwarding is working by sending a test email to your
UMB account a week from this coming Friday.
You must reply to this test message or you will lose 15 points
Remember, you will lose 2 points for every day that the assignment is late.
All homework assignments are posted at
http://www.cs.umb.edu/~tsoro/teaching/it244_html/hw_it244/homework_it244.html
Unless you hear otherwise, you should expect a homework assignment each week.
Completing the Apply Process
A few of you have not completed the Apply process.
You must fix this by going to the see the operators in the Unix Lab.
I will read out the names of those students who have not completed the Apply
process after taking attendance.
New Material
- We will cover most of the chapters in the textbook
- We will skip chapters 6 & 7 - the
vi and emacs editors
- These programs are text editors ...
- that are run at the command line ...
- They are used to create and modify text files
- Text files have no formating ...
- like you would find in Microsoft Word
- Text files only contain characters
- Chapters 6 & 7 show you how to use
vi and emacs
- But the best way to learn an editor is to use it ...
- not read about it in a book
vi and emacs are full featured text editors- You will need to use a text editor in this course ...
- to complete your homework and Class Exercises
- But
vi and emacs take some time to learn
- Instead of teaching you one of these editors ...
- I'll show you
nano, a simple text editor
nano is good enough for our purposes- You do not have to use
nano
- You can use any text editor that runs on Unix/Linux
- This rules out Notepad or Word
- I'll also skip chapter 9 which covers the TC shell ...
- because it is not used much these days
- We will use the Bash shell in this course
- Bash has more features than the TC shell
- Bash is the default shell in most Linux installations
- We will not be installing Linux in this course
- Modern installers are very good - almost idiot proof ...
- so installing Linux is little more than running the installer ...
- and answering a few simple questions
- If you want to install Linux on your machine ...
- and are having trouble ...
- you can get help from the Boston Linux User Group
- This group holds periodic "Installfests" at MIT
- where knowledgeable people can help you with the installation
- All work for the course will be done on a Linux machine ...
- running Ubuntu Linux 16.04
- We will only use the Windows machines in the Lab ...
- to connect to the Linux machine users3.cs.umb.edu
- You can use your laptop instead of a Windows machine ...
- to connect to users3.cs.umb.edu
Connecting to the Linux Machine from Home
Operating Systems
- The operating system
is the software that allows you to use a computer
- The textbook defines an operating system as
An operating system is the low-level software that schedules tasks,
allocates storage, and handles the interfaces to peripheral hardware,
such as printers, disk drives, the screen, keyboard, and mouse
- An operating system like a city government
- A city government provides resources - water, sewage, snow plowing
- It also provides protection - police and fire departments
- The operating system provides resources ...
- like access to memory, files and devices
- It also provides protection to keep one program ...
- from interfering with another ...
- and to keep other people from messing with your files
- Every computer has an operating system of some sort
- Nowadays computers are found in most of the durable goods you buy ...
- like cars and refrigerators
- You never see these computers ...
- but they are there making everything work properly
- These "invisible" computers are called embedded systems
- They too have operating systems ...
- but they are much simpler than those on a desktop or laptop
Components of the Operating System
- There are two components of an operating system
- The kernel is a program that is always running
- It controls all access to any hardware connected to the machine
- Every program that runs on a computer needs resources ...
- like memory and access to files
- It gets these resources from the kernel
- The kernel is like a traffic cop
- The kernel makes sure that two programs don't use the same resource ...
- at the same time
- Utilities are programs that allow you use and manage computer resources
Unix
- I will use the terms Unix and Linux interchangeably in this course ...
- but they are distinct
- Unix is an operating system developed as a research tool at Bell Labs
- Bell Labs was created as a research facility ...
- for the Bell telephone system
- Some of the most important advances of the 20th century ...
- came from Bell Labs
- Researchers there have won many awards ...
- including some very important Nobel Prizes
- Unix has a number of powerful features
- It is often used in academic, engineering and research environments
- Unix was developed before Graphical User Interfaces (GUIs) become common
- The Unix philosophy is to create many small programs ...
- that do one thing well
- Unix allows simple tools to be strung together ...
- to perform a complex task
- This allows people to write commands that do complicated things ...
- on the fly
- When first created, Unix was given away free to universities ...
- and many Computer Science students learned to use it ...
- and grew to like its power
- Talented programmers down through the years have made many contributions to Unix ...
- which improved it greatly
- This tradition continues with Linux
Different Unix Releases
- There is no single collection of software that can be called Unix or Linux
- A Linux/Unix distributions consist of
- The kernel is always present in the computer's memory ...
- and deals directly with the hardware ...
- like the CPU, memory and the hard disc
- A program cannot talk directly to the hardware ...
- but must do so through the kernel
- The utilities help you use the machine's resources
- Applications are programs that are used to get work done ...
- such as a word processor or an email client
- Over the years a number of different Unix distribution have appeared
- One popular Unix distribution is BSD ...
- which stands for Berkeley Software Distribution
- It was developed by the Computer Systems Research Group ...
- at the University of California at Berkeley
- Berkeley charges nothing for this Unix
- The BSD license is the least restricted open source license
- See
http://www.opensource.org/licenses/bsd-license.php for more information
- The Macintosh runs a customized version of Unix ...
- that comes mainly from BSD
- Another popular Unix distribution is Unix System V
- It was released commercially by AT&T ...
- the original corporate sponsor of Bell Labs
- There were four major releases of System V
- Release 4, abbreviated SVR4, enjoyed the greatest commercial success
- The Unix used at UMB was, until recently, Solaris
- Solaris was developed by Sun Microsystems as a commercial product
- Subsequently, Sun released most of the code base as an open source project ...
- called Open Solaris
- Sun was acquired by Oracle in January 2010
- We now use the Ubuntu Linux distribution at UMB
GNU and the Free Software Foundation
- Richard Stallman is a legendary figure in the Unix world
- He received a MacArthur "genius" grant
- He worked for many years at the MIT Artificial Intelligence Laboratory
- When Stallman started programming there was no software industry ...
- as we know it today
- The software came with the hardware ...
- and companies sometimes distributed the source code ...
- along with the machines
- Stallman and his associates liked this open environment ...
- where ideas could be shared freely
- In these early days, companies were not too concerned about trade secrets
- Stallman and his fellow programmers had access to the source code ...
- for the programs they used
- When a bug was discovered, they could look in the source code ...
- and fix the problem directly
- As the software industry became more commercialized ...
- companies refused to release their source code
- They wanted to sell software independently from the hardware ...
- and to do this they needed to keep the source code secret
- This this bothered Stallman
- He could no longer look at the source code ...
- to fix the bugs he found
- Instead, he had to report the bug to the company ...
- and then wait for a fix
- In 1983, Stallman announced plans for the GNU Operating System
- It would be distributed under the GNU License ...
- and would be compatible with Unix
- GNU is a recursive acronym ...
- that stands for "GNU is not Unix"
- In 1985 Stallman founded the Free Software Foundation
- It's mission was to develop GNU software ...
- and to advance the cause of free software
- By "free" Stallman meant that every user has the right to read ...
- and modify the source code
- It did not mean that an organization could not charge for the software
- The software was "Free as in speech, not beer"
- The Free Software Foundation charged a modest amount for its software
- Stallman's definition of free software is very strict ...
- and he distinguishes it from open source software
- Stallman has written books on the subject of free software ...
- which can be obtained from the
Free Software Foundation
- The GNU License is fairly elaborate
- If any person or company makes a change to software distributed under the GPL ...
- they must distribute the improved source code under the same license
- This means a company cannot take software distributed under the GPL ...
- make some improvements ...
- and then sell it as proprietary software
- The GNU project first focused on developing tools ...
- that could be used to write the software for the operating system
- Their most important contributions were the programmable text editor,
emacs ...
- and the compiler,
gcc
- Most of Unix is written in C ...
- so developing the GNU C compiler was an important first step
- Work on the kernel, the heart of the operating system ...
- was saved for last ...
- since it would be the most difficult
- The GNU kernel was to be named Hurd
Linus Torvalds
- In the early 90's as Linus Torvalds was working on his Masters thesis
- At this time he began a personal project ...
- that eventually became a Unix-like kernel
- He released the source code for this kernel to the public
- Many programmers looked at this code and liked it
- They sent in improvements which Linus added to the code
- This improved kernel was widely in open source circles
- Together with many of the GNU tools ...
- it formed the core of what came to be called Linux
- Today Linus Torvalds is the chief architect of the Linux kernel
Linux Distributions
- There are many Linux distributions ...
- each released by a different group
- Each distribution consists of different choices ...
- from various software packages ...
- for each component of the operating system
- The two most common distributions are Ubuntu and Red Hat
- CentOS is a noncommercial Linux distribution ...
- which uses source code provided by Red Hat for their commercial Linux distribution
Ubuntu
- The machine we'll be using in this class is users3
- It is a virtual machine running Ubuntu 16.04.1 LTS
- Ubuntu is based on Debian Linux
- Development of Ubuntu is led by Canonical ...
- a company based on the Isle of Man in Great Britain ...
- and owned by South African entrepreneur Mark Shuttleworth
- Ubuntu is named after the Southern African philosophy of ubuntu ...
- which is often translated as "humanity towards others"
- A new Ubuntu version is released every 6 months
- The Ubuntu version number is composed of the year and month of its release
- So version 16.04 was released in April of 2016
- LTS stands for "Long Term Support"
- An LTS version will be supported for 5 years after its release
- A new LTS version is released every 2 years
- Every Ubuntu release also has a name
- The name consists of two words:
- An adjective
- An animal whose name shares the same first letter
- The name for Ubuntu 16.04 LTS is "Xenial Xerus"
- A xerus is an African ground squirrel
- Xenial means friendly relations between hosts and guests
- One of the reasons for Ubuntu's success is its package manager
- If you type in a command that is not installed ...
- Ubuntu will suggest packages that will install the software
Shells
- The shell
is the program you are talking to ...
- when you type something at the command line
- The shell listens to what you type at the command line ...
- and asks the kernel to execute the commands you entered
- The shell is the program you use to talk to the kernel
- Only the kernel can create the
process ...
- that is a running program
- Modern shells provide a number of features that make them easier to use
- Down through the years there have been a number of different Unix shells
- Today, the two most common shells are the TC shell and Bash
- We will be using Bash in this course
Unix Commands
- To run a Unix command you go to the command line ...
- type the name of the command ...
- followed, perhaps, by options and arguments ...
- and then hit Enter ...
- or Return on a Mac
- Options change what the command does
- For example the
ls command lists the contents of a directory
$ ls
foo.txt it244 work
- When
ls is used with the -l (for long) option ...
- more information is presented
$ ls -l
total 3
-rw-r--r-- 1 it244gh libuuid 16 2012-06-26 16:19 foo.txt
lrwxrwxrwx 1 it244gh libuuid 34 2012-02-07 09:46 it244 -> /courses/it244/s12/tsoro/it244gh
drwxr-xr-x 2 it244gh libuuid 512 2012-06-27 11:08 work
- Arguments are the things on which the command operates
- If
ls is given the name of a directory as an argument ...
- it will display the contents of that directory
$ ls html
it244_sum17_html it341_f16_html
- Most Unix/Linux commands are very short, to save typing ...
- and usually have mnemonic value
- For example,
ls stands for "list"
Today's Class Exercise
- Today you will use the Windows machines in the Lab ...
- or your laptops ...
- to connect to the virtual machine users3
- You will find the instructions on the Class Exercise
- If you have not completed the apply process ...
- you will not be able to log in
- We'll be using the Linux machine named users3 ...
- for all our work in this course
- In today's Class Exercise, you will enter your first Unix commands
- The Class Exercise will tell you what do to ...
- and what commands to enter at the command line
- Type the commands specified, including any options ...
- and then the arguments, if any
- Options are proceeded by a -
or >--
Attendance
Apply Delinquents