This is Alan Pope with the second screencast in the
Ubuntu Month of Screencasts.
All of the screencasts in this month can be downloaded for free from
our website, which is screencasts.ubuntu.com
In this screencast we are going to talk a little bit about Linux.
We won't go into massive detail about how it is programmed
or what it is made up of,
just some high level stuff to familiarise people.
The first thing to mention is this guy, Linus Torvalds.
He is the guy who began the Linux project
started back in nineteen ninety-one,
as a hobby to scratch an itch.
He wanted to have a Minix-like operating system at home.
So initially Linux wasn't developed to be a competitor with
any other product out there.
It merely to achieve something that Linus wanted to do at home
on his own computer.
So, Linux is an operating system
and an operating system is the software that manages
the sharing of resources in a computer.
So what are those resources?
Well the kinds of resources that we are talking about
is the hardware inside the computer and
some of the peripherals that are attached to the computer.
This might be the CPU, where the Linux kernel will decide
what programs get access to the CPU and when.
and how much of the CPU they get.
It could be the memory, the kernel decides how much of memory
gets allocated to one particular program and when that memory gets given back.
In addition it can allocate space on disk and lay out format on the disk
and also decide what to do with packets of information that flow
across the network.
So the Linux kernel is an operating system and the operating system
manages some of these hardware resources.
That is kept separate from the applications that run on top of the kernel.
These programs are often called user space programs.
There are whole load of user space programs
that are written to run under Linux.
Some of them are called the GNU tools.
GNU was created by this man, Richard Stallman.
GNU stands for GNUs Not Unix.
We will talk more about the GNU GPL licence and a little bit more about GNU
in the next screencast, when we talk about licences.
Suffice to say Linux is licenced under the GPL,
which is a very permissive licence, allows people to copy it,
make changes to it, redistribute it and so on.
This guy is called Tux. He is a penguin, as you can see.
He is the mascot of the Linux kernel.
So you might see this image on websites that are Linux oriented
or you might see them on products.
For example I bought this device a couple of weeks ago.
and I was surprised to see on the box "works with Linux" and
has a little picture of Tux the penguin on there.
Which is great because it is showing people that this hardware
will work with Linux based computers.
It is worth noting that Linux actually supports a vast amount of hardware
out of the box.
Probably more than most other operating system, certainly more than Windows
and certainly more than Mac OS X.
The hardware support is great within Linux for a large number of devices
and you can actually install Linux on a large number of devices.
For example we have here a server, a desktop PC and a laptop,
which can all run Linux.
We also have devices that you would not traditionally think of as a computer
like a personal video recorder, TV recorder, mobile phone, a media player
and also portable tablet PCs and the one laptop per child,
the green computer at the top is an OLPC.
They all run Linux.
You can get Linux from the kernel archive website, which is kernel.org
What you can get here is the source code, the actual program code
that can be compiled into a runable program
But most people do not do that, most people take their kernel from elsewhere.
You can get your kernel from the vendor of your Linux distribution
Here are a few Linux distributions and they all have one thing in common,
which is they have, well they have many things in common,
but one of the things they have in common is that there is Linux at the heart,
the heart of all of these distributions.
So on top of Linux they all supply GNU utilities and other applications.
Those applications are compiled to run on Linux.
Another distribution, my particular favourite, is Ubuntu
and this also has Linux, the GNU tools and a load of other applications,
which we will look at in just a minute.
First of all let us take a look at the history of some of these Linux distributions
There is a great diagram you can view online,
which gets updated regularly.
It is the GNU/Linux distribution timeline
If we just scroll up to the top of this very large image
you can see the URL is futurist.se/gldt
I will put that link on the website.
You can see that it dates from nineteen ninety-two all the way
through to present day two thousand and seven.
If we scroll down a little we can see some of the early Linux distributions
and the little dot dot dot means that they are no longer supported
or they are not being used as much any more.
There is one that is, SLS, which is now Slackware Linux,
which is very popular.
You can see as we scroll across, it is still used
and there are derivatives of Slackware.
Further down we have Red Hat, which is also very popular.
and there are many derivative distributions of Red Hat.
We can see one example here Red Flag.
Red Flag Linux is based on Red Hat, designed specifically for one particular market.
one particular geographic region, for example.
There you can see Red Hat itself, the main line through the middle,
it is still maintained through today.
Another distribution that was popular in the early days
and is still popular now, is Debian.
Debby and Ian's distribution.
You can see here, this has also spawned a number of derivatives
including Ubuntu and it's derivatives Edubuntu, Xubuntu and Kubuntu.
Ubuntu itself has also spawned derivatives like gNewSense.
and Linux Mint
So that just shows you a little snapshot of what
the history of the Linux distributions are.
The distribution I use is Ubuntu.
And as I said Ubuntu uses at it's core the Linux kernel.
With each release of Ubuntu there is a newer version of the kernel supplied.
This is a slightly modified version of the kernel than the one you get from kernel.org.
So on the left hand side you can see the versions of Ubuntu
that have been released.
The ones that are crossed out are no longer supported.
On the right hand side you can see the version of the Linux kernel that is supplied.
We each successive version of Ubuntu we get a newer version of the kernel
and the newer version of the kernel provides additional drivers,
newer functionality, better resource management,
better power management and so on and so on.
The latest version of Ubuntu is seven ten,
otherwise known as Gutsy Gibbon
and uses kernel two six twenty-two.
Which works very well on laptops for example.
On top of the Linux kernel, which is symbolised with a little penguin,
we also have the GNU tools
and we have loads of other applications.
These other user space applications that sit on top of Linux.
We have got the GNOME desktop environment,
Tomboy note taking, Firefox web browser,
GIMP image editor, Evolution email client,
F Spot photo management,
SANE for managing your scanners,
Ekiga for doing voice over IP,
Pidgin for doing instant messaging
and Python if you wanted to do some development.
All of that gets packaged up as a distribution
and that distribution is Ubuntu.
Now you do not generally communicate with kernel directly
you use these user space applications.
But I will give you an example of where you might
see some interaction with the kernel.
Here is an example, if I go to System, Administration,
System Log, on Ubuntu.
We see messages on my machine, which is called wopr.
and the messages are coming from the kernel.
You can see on the right hand side all this
strange text is information from the kernel.
If I do somthing like unplug my USB webcam,
you can see a message appears at the bottom of this log
saying USB disconnect.
If I plug it back in again,
my webcam is recognised and registered
and you can see there it is a Philips 740 ToUcam.
Let us just prove that it works
If I open a handy webcam application here
and connect to my Philips 740 webcam
choose an apropriate resolution
Remember the driver for this is inside the kernel.
So this application doesn't need to know what camera I have got.
He is a handsome fellow, isn't he?
Hello!
Now if we just save a snapshot of this for later.
If I go to my home directory.
You can see the webcam works.
Marvelous!
So I used a user space application
to communicate with a device,
the driver was provided by the kernel.
Thanks very much for watching,
all of our screencasts are available on the website,
screencasts.ubuntu.com