Finally, for reasons of homogeneity and ease of administration, the same distribution must run on all the servers (some of which are Sparc machines, currently running Solaris) and office computers.
2.4.1. Commercial and Community Driven Distributions
There are two main categories of Linux distributions: commercial and community driven. The former, developed by companies, are sold with commercial support services. The latter are developed according to the same open development model as the free software of which they are comprised.
A commercial distribution will have, thus, a tendency to release new versions more frequently, in order to better market updates and associated services. Their future is directly connected to the commercial success of their company, and many have already disappeared (Caldera Linux, StormLinux, etc.).
A community distribution doesn't follow any schedule but its own. Like the Linux kernel, new versions are released when they are stable, never before. Its survival is guaranteed, as long as it has enough individual developers or third party companies to support it.
A comparison of various Linux distributions led to the choice of Debian for various reasons:
It is a community distribution, with development ensured independently from any commercial constraints; its objectives are, thus, essentially of a technical nature, which seem to favor the overall quality of the product.
Of all community distributions, it is the most significant from any perspective: in number of contributors, number of software packages available, and years of continuous existence. The size of its community is an incontestable witness to its continuity.
Statistically, new versions are released every 18 to 24 months, a schedule which is agreeable to administrators.
A survey of several French service companies specialized in free software has shown that all of them provide technical assistance for Debian; it is also, for many of them, their chosen distribution, internally. This diversity of potential providers is a major asset for Falcot Corp's independence.
Finally, Debian is available on a multitude of architectures, including Sparc; it will, thus, be possible to install it on Falcot Corp's several Sun servers.
Once Debian has been chosen, the matter of which version to use must be decided. Let's see why the administrators have picked Debian Squeeze.
2.5. Why Debian Squeeze?
At the time of this writing, Debian Squeeze was still the “Testing” distribution, but now, while you are reading, it will be the new “Stable” version of Debian. This is also the reason for which we speak of “Debian Squeeze”, rather than “Debian 6.0”, since the version number is not used prior to its effective release.
You may note a few minor differences between what is written here and what you observe in practice, even though we have limited these discrepancies as much as possible.
PARTICIPATE
Do not hesitate to indicate any error herein to us by e-mail; You can reach Raphaël at <hertzog@debian.org>, and Roland at <lolando@debian.org>.
The choice of Debian Squeeze is well justified based on the fact that any administrator concerned about the quality of their servers will naturally gravitate towards the stable version of Debian. Furthermore, this distribution introduces numerous interesting changes: support for the latest virtualization technologies (KVM), simplified PAM configuration, an improved installer supporting BTRFS, all bringing improvements that directly affect administrators.
Chapter 3. Analyzing the Existing Setup and Migrating
Any computer system overhaul should take the existing system into account. This allows reuse of available resources as much as possible and guarantees interoperability of the various elements comprising the system. This study will introduce a generic framework to follow in any migration of a computing infrastructure to Linux.
3.1. Coexistence in Heterogeneous Environments
Debian integrates very well in all types of existing environments and plays well with any other operating system. This near-perfect harmony comes from market pressure which demands that software publishers develop programs that follow standards. Compliance with standards allow administrators to switch out programs: clients or servers, whether free or not.
3.1.1. Integration with Windows Machines
Samba's SMB/CIFS support ensures excellent communication within a Windows context. It shares files and print queues to Windows clients and includes software that allow a Linux machine to use resources available on Windows servers.
TOOL Samba
Samba version 2 behaves like a Windows NT server (authentication, files, print queues, downloading printer drivers, DFS, etc.) Version 3 works with Active Directory, brings interoperability with NT4 domain controllers, and supports RPCs (Remote Procedure Calls). Version 4 is a rewrite (still experimental), the purpose of which is to provide functionality of a domain controller compatible with Active Directory.
3.1.2. Integration with Mac OS machines
Netatalk is a program which uses the Appletalk protocol (running on a Linux kernel) and allows Debian to interface with a Mac OS network. It ensures the operation of the file server and print queues, as well as time server (clock synchronization). Its router function allows interconnection with Appletalk networks.
3.1.3. Integration with Other Linux/Unix Machines
Finally, NFS and NIS, both included, guarantee interaction with Unix systems. NFS ensures file server functionality, while NIS creates user directories. The BSD printing layer, used by most Unix systems, also allows sharing of print queues.
Figure 3.1. Coexistence of Debian with MacOS, Windows and Unix systems
3.2. How To Migrate
In order to guarantee continuity of the services, each computer migration must be planned and executed according to the plan. Whatever the operating system used, this principle never changes.
3.2.1. Survey and Identify Services
As simple as it seems, this step is essential. A serious administrator truly knows the principal roles of each server, but such roles can change, and sometimes experienced users may have installed “wild” services. Knowing that they exist will at least allow you to decide what to do with them, rather than delete them haphazardly.
For this purpose, it is wise to inform your users of the project before migrating the server. To involve them in the project, it may be useful to install the most common free software programs on their desktops prior to migration, which they will come across again after the migration to Debian; OpenOffice.org and the Mozilla suite are the best examples here.
3.2.1.1. Network and Processes
The nmap tool (in the package with the same name) will quickly identify Internet services hosted by a network connected machine without even requiring to log in to it. Simply call the following command on another machine connected to the same network:
$ nmap mirlaine
Starting Nmap 5.00 ( http://nmap.org ) at 2010-07-29 16:36 CET
Interesting ports on mirlaine (192.168.1.99):
Not shown: 1694 closed ports
PORT STATE SERVICE
22/tcp open ssh
79/tcp open finger
111/tcp open rpcbind
Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds
ALTERNATIVE Use netstat to find the list of available services