           Choosing the FreeBSD Version That Is Right For You

  The FreeBSD Documentation Project

   Copyright (c) 2005 The FreeBSD Documentation Project

   $FreeBSD:
   doc/en_US.ISO8859-1/articles/version-guide/article.sgml,v 1.16
   2012/03/13 13:38:43 ryusuke Exp $

   FreeBSD is a registered trademark of the FreeBSD Foundation.

   So you have chosen to install FreeBSD. Welcome! This document is
   designed to help you to decide which version to install.

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1 Background

   To decide which version of FreeBSD is the best for your needs, it
   is important to understand a few concepts about our development
   and Release Engineering (RE) processes.

   FreeBSD is developed by a large group of individuals who are
   almost entirely volunteers. The source code to the kernel and the
   most common libraries and utilities is maintained in a source
   control system and available for the general public to download at
   any time. Separately, compiled versions (binaries) are made
   available on a recurring basis. Some of these binary versions
   undergo an extensive testing process and are then termed a
   release.

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  1.1 Releases

   Releases are named with a major version number and minor version
   number.

     * The goal of a major release is to introduce a set of new
       features. Inevitably, as new features are added to FreeBSD, or
       as older features are no longer useful or are dropped, it is
       sometimes necessary to break compatibility with previous major
       releases.

     * The goal of a minor release is primarily to fix bugs and
       improve performance and stability. Keeping both source-level
       and binary compatibility from one minor release to another is
       a priority. On occasion, new features may be added to a minor
       release when it is believed that these other goals will not be
       compromised.

   However, keep in mind that a "release version" is merely a
   snapshot of the source tree at a particular point in time which is
   given a particular name (or tag). (For instance, the tag that
   Release Engineering assigned for the 5.4 release was
   RELENG_5_4_0_RELEASE.) Development always continues on what is
   known as the HEAD tag.

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  1.2 Branches

   At the time of each release, a branch is created, such as
   RELENG_5_4. Although the source files named by
   RELENG_5_4_0_RELEASE will never change, those on RELENG_5_4 can,
   by the adoption of changes from HEAD such as fixes for security
   and other bugs.

   During the life of each major release, another tag is created such
   as RELENG_5. In addition to security and other bug fixes, other
   new changes can be brought in from HEAD so as to constitute the
   changes for the next minor release in the sequence.

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  1.3 STABLE versus CURRENT

   During the lifetime of each major release, an individual branch
   may also be termed STABLE. This indicates that the FreeBSD Project
   believes that the branch is of sufficiently proven quality to be
   used by a wide range of users. Branches that need further testing
   before being widely adopted are named CURRENT.

     Note: The FreeBSD Project cannot in and of itself guarantee that
     the software that it ships is stable enough for any given
     installation. Only each individual user can make that decision.
     Please keep in mind that the Project is primarily composed of
     volunteers and is not able to offer any kind of warranty of
     fitness.

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  1.4 Ports versus Packages

   Separately from the files distributed above, FreeBSD supports
   thousands of applications that are developed by third parties
   outside of the project itself. (Examples include windowing
   systems, Internet browsers, email programs, office suites, and so
   forth.) In general, the project itself does not develop this
   software, only the framework to allow these programs to be
   installed (termed the Ports Collection). Applications may be
   installed either from source, if its licensing terms allow such
   redistribution (these are called ports), or as compiled binaries
   if allowed (these are called packages).

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2 Release Scheduling In The Past

   During the development and release of FreeBSD 5.X, many lessons
   were learned which only became clear in retrospect. The goals of
   the 5.X series were very aggressive, and included:

     * To provide support for Symmetric MultiProcessing (SMP)
       machines;

     * To increase performance by adopting a new strategy for dealing
       with resource contention in the kernel;

     * To add several new processor architectures;

     * To introduce a new threading model;

     * To introduce a new scheduler;

     * To add support for new technologies such as power management
       (especially important for laptops); and, most critically,

     * Not to declare the release series as STABLE until all these
       tasks were finished.

   This led to a situation where it was several years between the
   time that a release in the 4.X series was declared STABLE and that
   a release in the 5.X series was declared STABLE. This had several
   undesirable effects:

     * The number of simultaneous feature-set changes made it very
       difficult to isolate one set of changes for merging back into
       the STABLE branch;

     * which meant that users who absolutely had to have certain new
       features (for instance, to be able to run on modern hardware)
       wound up adopting (for instance) FreeBSD 5.2.1 even though it
       was advertised as a developer-only release, and regardless of
       the fact that a CURRENT release was not really suitable for
       their needs.

     * In the cases where backmerges were made, this put the
       developers in a position of trying to support features on a
       version that they themselves were not using as their primary
       development platform.

     * The time lag also meant that when 5.3 was finally declared as
       the latest STABLE release, the accumulated weight of changes
       made the upgrading process very painful.

   To put it bluntly, no one was satisfied with this result.

   The lessons that were learned are:

     * New major releases must have a smaller number of feature-set
       changes and be released more often.

     * To the maximum extent possible, feature-set changes should be
       isolated from each other. (This implies that some development
       must take place outside of the main tree and only be merged in
       when it will not destabilize other simultaneous development.)

     * Major releases should be targeted at a time deadline rather
       than a feature-set deadline. If some feature is not ready in
       time, then it should be disabled by default and left for the
       next major release.

   By releasing smaller sets of changes more often, it is also hoped
   that less time will be spent trying to merge features from HEAD
   back into the latest STABLE version (and thus trying to support
   those features in more than one major version); and further, that
   as the changes are more isolated, that the risk of introducing
   more bugs by doing so is much less.

   Also, by focusing on a time deadline rather than a feature set, it
   should finally be possible for users, developers of external
   applications, and the FreeBSD developers themselves to be able to
   better plan for the future.

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3 Release Scheduling Goals Going Forward

   Here are the current scheduling goals for the Project:

     * To release a new major release every 18 months;

     * To release a new minor release every 4 months;

     * To provide prebuilt packages for the most recent minor release
       of each major version;

     * To provide security updates and other critical bug fixes for
       the last several minor versions of each major version (termed
       security branches).

   Due to the large number of possible combinations of installable
   versions, it is not possible to support every version
   indefinitely; this is due somewhat to the availability of machine
   resources but primarily due to the amount of volunteer effort that
   is available.

   Interested readers should also see:

   http://www.FreeBSD.org/releng/index.html#schedule

           The Release Engineering Schedule

   http://www.FreeBSD.org/security/security.html#supported-branches

           The Security Branch Schedule

   These documents go into much greater depth about the background
   and rationale behind the decisions regarding the supported
   branches and the lifetime of each branch.

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4 How Do These Factors Affect My Decision?

   The major factors that should affect your decision as to which
   version to install include:

     * What degree of stability does your installation need?

     * How much effort do you wish to devote to upgrading?

     * How long do you intend to stay on a particular version between
       upgrades?

     * How important is security to your installation?

     * Will you be installing from source, or from binaries?

     * Are you willing to help participate in the FreeBSD development
       process?

   Here are some rough guidelines to help you in your decision:

     * If you have a short-term need, would benefit from the highest
       degree of stability currently available, and are not able to
       devote many resources to upgrading, then you will probably
       want to install the latest STABLE minor release and remain
       with that. Depending on your security needs, you may or may
       not wish to track changes to that branch as they are released.

     * If you have a short-term need, and feature completeness or the
       best levels of security are most important to you, and you are
       willing to spend time upgrading, you may wish to track the
       latest STABLE branch.

     * If you are not immediately planning on going into production,
       you are willing to work through a certain number of problems,
       and a new major release is upcoming within the next few
       months, you may wish to investigate installing that branch to
       help the project to test it and stabilize it to make it the
       best release possible in the medium to long term.

     * Only if you are willing to install from source, and spend time
       debugging problems with the base system and follow up with
       problem reports, and track the mailing list that deals with
       such issues, should you consider tracking HEAD.

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5 Conclusion

   We hope that this article serves as a useful starting point for
   understanding the FreeBSD development model and deciding what
   version is right for your needs.

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