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Ubuntu

ubuntu

Ubuntu is a free GNU/Linux distribution f(o)unded by Mark Shuttleworth and sponsored by Canonical Ltd. It focuses on ease-of-use, hardware support and functionality, but is still devoted to free software ideals. It is currently one of the most popular GNU/Linux flavors with very strong online community.

Pic 1. Ubuntu - random desktop

Ubuntu mission

The Ubuntu mission is as follows:

The Ubuntu community is built on the ideas enshrined in the Ubuntu Philosophy: that software should be available free of charge, that software tools should be usable by people in their local language and despite any disabilities, and that people should have the freedom to customize and alter their software in whatever way they see fit.

Ubuntu is special in a few ways. It has regular, predictable releases, every 6 months with Long Time Support (LTS) releases every 1.5 years. It is fast and easy to install thanks to the LiveCD installer. It's useful just after installation since it installs all the commonly used desktop applications altogether. Specialized software can be easily added using the predefined repositories. And finally is has a fine community and support (mailing list, IRC channel and web forums).

Ubuntu is based on Debian GNU/Linux and uses a lot of its tools and packages.

"Ubuntu" is an ancient African word meaning "humanity to others".

User experience

User interface of Ubuntu (GNOME desktop) is very coherent and aesthetic. Apart from standard GNOME applications, a few external open-source killer-applications are included by default, like OpenOffice.org, Firefox and GIMP. The system detects popular mobile devices automatically (e.g. USB stick, digital cameras and memory cards). Its great hardware detection capabilities are especially visible on laptops where technologies like WiFi, software suspend or ACPI used to cause problems on GNU/Linux systems. Not anymore.

Included software

Ubuntu divides all software into 6 categories.

Main — includes supported free software (all software included on install CDs plus some additional packages, usually one application for a task).
Restricted — included supported non-free software (mainly drivers and fonts).
Universe — unsupported free-software (community-driven repository with thousands of free software apps).
Multiverse — unsupported non-free software (community-driven repository with things like restricted audio and video codecs or free (as in beer) but proprietary applications like Adobe Reader, etc.).
Commercial — commercial software (right now included Opera Browser and Real Player).
Backports — repository for software included in newer versions of the OS, targeted at users who need to stick to the older version of Ubuntu but still want a few recent programs.

Main and Restricted repositories are activated by default. Other need to be turned on manually, either by editing /etc/apt/sources.list or choosing the right checkboxes in Synaptic Package Manager.

Ubuntu flavors

Ubuntu is not GNOME-only. Other desktop environments are available as well. There are specialized versions of Ubuntu featuring KDE, XFCE, Fluxbox, IceWM and e17. All of those can be installed and used in regular Ubuntu, as well.

Ubuntu is available in 4 major versions:

Default Ubuntu — featuring GNOME and lots of GNOME applications like Evolution, Synaptic Package Manager, Beagle Search, Rhythmbox, Sound Juicer, etc. — this is the original flavor and the most polished and stable one.
Edubuntu — a GNOME desktop for kids and children, with games and educational applications.
Kubuntu — a flavor of Ubuntu featuring KDE as the default desktop, with KDE applications like Kontact, Adept Package Manager, Amarok, K3B, etc.
Xubuntu — the youngest version of Ubuntu with XFCE as the default desktop — this is a lightweight version for older hardware computer users.

There are also a few more versions of Ubuntu which are not officially part of the project, to name only: Fluxbuntu (with Fluxbox as a WM), nUbuntu (focused on providing security tools), Ubuntu Christian Edition aka Christianbuntu, Ubuntu Studio for multimedia editing, and more.

External Ubuntu resources

News

Documentation, guides and tips

Software

Download

Adobe Acrobat 7.0 Reader for Linux

After the download is complete, quit your Web browser.

Double-click the newly downloaded file "AdbeRdr70_linux_enu.tar.gz" and follow the instructions on your screen.

Uncompress or gunzip the file.

Untar the file and read the text file for specific installation steps.

The installation procedure will ask you to read and accept the Electronic End-User License Agreement.

Code

http://ardownload.adobe.com/pub/adobe/reader/unix/7x/7.0/enu/AdbeRdr70_linux_enu.tar.gz

IP Addressing

In today's world of inter-connected computers, you may have a connection to hundred of thousands of other machines. Granted there is no single cable connecting all of these computers, however there is a logical connection in that you can use the telnet program from your PC in California and connect to a machine in Germany. The problem is, how do the packets get from one end to another. Added to that, how do you keep your local network in California from getting overloaded with packets that are being sent between machines in Germany and at the same time making sure that those telnet packets do get through? The answer is provided by the Internet Protocol (IP).

Just as a street address is not always sufficient to get your letter delivery, so is the IP not always sufficient to get the packet delivered. If I sent you a letter, it could be sent to a single, central post office, whose job it was to distribute mail throughout the entire US. Because of the incredibly large number of pieces of mail, this is impractical. Instead, there are thousands of offices, all over the country, whose job it is to route the mail for us.

If we lived in a small town, the local post office could catch a letter destined for a local address before it goes further. Mail with addresses outside could be sent to other post offices to be processed.

A similar situation applies to IP addresses. In local, self-contained networks, the IP address alone is sufficient. However, when multiple networks are combined, machines spend more time trying to figure out if the packet belongs to them than actually processing information. The solution is a network mask. Just as a zip code tells a postal worker whether to process a particular piece of mail locally or not, the network mask (or netmask) tells machines whether or not they can simply ignore a packet or need to process it further. How this works, we'll get to in a moment.

Every machine on the network, needs to have its own, unique IP address. Just like every house has a unique mail address. If that network is connected to the rest of the world, that address must not only be unique within the local network, but unique within the rest of the world, as well. With the most common IP version (IPv4), IP addresses are 32-bit values. They are usually represented by four sets of numbers, ranging from 0-255 separated by dots (.). This is referred to as dotted-decimal notation. In dotted-decimal notation, an address might look like this:

147.132.42.18

Since each of these numbers range between 0-255, they can be represented by eight bits and are therefore referred to as an octet. This IP address is often thought of as being composed of a network portion (at the beginning) and a node (or machine) portion at the end. This would be comparable to writing a street address as:

95061.Main_Street.42

Where 95061 is the zip code and Main Street is the street and 42 is the address on that street. The reason we write the street address in this fashion, is that it's common to think of the IP address as moving from the general to the more specific.

Currently, there are three classes of networks in common use, which are broken down by both the range used in the first octet and the number of octets used to identify the network. Class A networks are the largest and use the first octet as the network address. Networks in the class will have the first octet in the range 1-126. Class B networks used the first two octets, with the first being in the range 128-192. The smallest networks, class C use the first three octets in the network address and with the first in the range 192-223. How IP addresses are broken down by the different network classes is shown in Table 0\1.

Class Range within 1st octet Network ID Host ID Possible networks Possible hosts per network
A 1-126 a b.c.d. 126 16,777,214
B 128-191 a.b c.d 16,384 65,534
C 192-223 a.b.c d 2,097,151 254
Table - IP Address Breakdown by Network

There are a couple of things I would like to point out about this table. First, the network address 127 represents the local computer, regardless of what network it is really on. This is helpful for testing as well as many internal operations. Network addresses 224 and above are reserved for special purposes such as multicast addresses. The terms "possible networks" and "possible hosts per network" are those that are calculated mathematically. In some cases, 0 and 255 are not acceptable values for either the network address or the host address. However, 0 can be used in a network address for either the second or third octet (for example, 10.2.0).

Keep in mind that a Class A address does not necessarily mean that there are 16 million hosts on a single network. This would be impossible to administrate and would over burden most network technologies. What normally happens is that a single entity, such as Hewlett-Packard is given a Class A address. They will then break it down further into smaller sub-nets. We'll get into more details about this shortly.

A network host uses the network ID and host ID to determine which packets it should receive or ignore and to determine the scope of its transmissions (only nodes with the same network ID accept each other's IP-level broadcasts). Because the sender's IP address is included in every outgoing IP packet, it is useful for the receiving computer system to derive the originating network ID and host ID from the IP address field. This is done by using subnet masks, as described in the following section.

In some cases, there is no need to have unique IP addresses, since the network will never be connected to the rest of the world. For example, in a factory where the machines communicate with each other via TCP/IP. There is no reason for these machines to be accessible from the Internet. Therefore, there is no need for them to have an official IP address.

You could just randomly assign IP addresses to these machines and hope that your router is configured correctly not to route the packets from these machines. One slip and you have the potential for not only messing up your own network, but someone else's as well.

The solution was provided in RFC-1918. Here, three sets of IP address were defined for use in "private" networks. These won't be routed and there is no need to coordinate their use with any of the registrations agencies. The IP addresses are:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

As you can see that there is just a single class A address, but 16 class B and 255 class C networks. Therefore, no matter what size your network is, you can find a private network for your needs.

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