Gentoo Linux, Based on the Portage Management System

The Gentoo Linux operating system is a Linux distribution based on the Portage package management system. The development project and its products are named after the Gentoo penguin.

Gentoo package management is designed to be modular, portable, easy to maintain, flexible, and optimized for the user's machine.

Packages are normally built from source code, continuing the tradition of the ports collection, although for convenience, some large software packages are also available as precompiled binaries for various architectures.

History.

Gentoo was initially created by Daniel Robbins as the Enoch Linux distribution. The goal was to create a distribution that was built from source code, tuned to the hardware, only included required programs, and decreased maintainer workload through scripting. At least one version of Enoch was distributed: version 0.75, in December 1999.

Compilation issues revealed problems with the GNU Compiler Collection (gcc), used to build from source code. Daniel Robbins and the other contributors experimented with "forked" versions of gcc, finding a version that gave a 10% to 200% speed increase over the "official" gcc. At this point, Enoch gained a reputation for its speed, prompting the name change to Gentoo Linux (the Gentoo species is the fastest swimming penguin). The modifications eventually became part of the official gcc (version 2.95), and other Linux distributions experienced similar speed increases.


After problems with a bug on his own system Robbins halted Gentoo Linux development and switched to FreeBSD for several months, later saying "I decided to add several FreeBSD features to make our autobuild system (now called Portage) a true next-generation ports system."

Robbins had wanted Gentoo Linux to become a commercially successful project, but found an appropriate business model difficult to achieve. In 2004 he set up the non-profit Gentoo Foundation and transferred all copyrights and trademarks to it and stepped down as Chief Architect of the project.
The current board of trustee contains 5 members who were announced (following an election) on October 21, 2006. There is also a subsidiary 7 member Gentoo Council whose members decide on global issues and policies. The current Council members were elected over the period of August 17, 2007 to September 17, 2007 by 117 active Gentoo developers.

Recently, the Gentoo Foundation charter was revoked, and reinstatement is underway.

Portability

Although originally designed for the x86 architecture, it has been ported to many others and currently runs on the x86, x86-64, IA-64, PA-RISC; PowerPC, PowerPC 970, SPARC64, MIPS, DEC Alpha, System Z/s390, PS3 Cell Processor and SuperH architectures. Official support for 32bit Sparc hardware has been dropped. Gentoo was the first distribution to offer a fully functional 64-bit Linux computing environment (user space and the kernel) for the PowerPC 970.

There is also a "Gentoo for Mac OS X" project which allows Mac OS X users to use Gentoo's Portage to install packages, similar to the way provided by Fink. Although still a work in progress, this project can coexist with Fink because it uses the same environment as Mac OS X instead of creating a new one.

Portability toward other operating systems, such as BSD-derived ones, is under active development by the Gentoo/ALT project. The Gentoo/FreeBSD project already has a working release, while Gentoo/NetBSD, Gentoo/OpenBSD and Gentoo/DragonFly are being developed. There is also a project to get Portage working on the GNU Hurd (although development is slow) and OpenSolaris.

Portage

Portage is Gentoo's package management system. It is similar in idea to the BSD ports collections: the original design was based on FreeBSD ports. In contrast, the Portage tree does not contain directories of Makefiles, but of so-called ebuilds, bash scripts that describe separate functions to download, configure, make, install and remove a package and additional functions that can be used to set up the operating environment for a package.

Portage is also the name of Gentoo's default package management utility package. This package provides, among other useful scripts, the emerge utility, which is written in Python and can be used by privileged users to easily inspect and alter the set of installed packages on a Gentoo operating system. Whereas emerge used to operate in a similar way to other ports collections, by entering a directory in the tree and using emerge (instead of make) to perform package management operations, it now reads variables from the file /etc/make.conf (again similar to ports) to determine where the Portage tree is kept.

Recently, alternative package management utilities like Paludis and pkgcore have seen heavy development. Both are intended to be used alongside or instead of the official Portage utilities in both development and practical use. As both competing projects intend to replace the official utilities, an effort has been raised to standardise the application programming interface of ebuilds for all package managers, in a project called the Package Manager Specification or PMS

Installation.

Gentoo may be installed in several ways. The most common way is to use the Gentoo LiveCDs. As with many Linux distributions, it can also be installed by most LiveCDs and existing Linux installations.

Installation of Gentoo can be completed by following the Gentoo Handbook. Additionally, several other methods of installation are listed in the Alternative Installation Method HOWTO; most of which are targeted at experienced users or users unable to boot from the Gentoo live CD.

As of version 2006.0, the Gentoo Foundation has released a GTK+ based installer to greatly simplify the process of installing the distribution from scratch.More advanced users will note that the new installer also brings back the stage 1 installation (see below) as a common installation method.

Advantages

Soft dependencies

Since packages are built by source, dependencies between packages are more flexible than for binary distributions, and can be explicitly enabled or disabled in many cases. Binary distributions typically offer similar flexibility by providing several versions of the same package under different aliases, or by splitting packages into more modular components where possible. Since the number of possible configurations becomes combinatoric as the number of compile-time options increases, it is not feasible to store binaries for all possible combinations. Gentoo is thus able to offer a greater variety of compile-time package options where other popular distributions are not.

Bleeding edge packages

By regularly syncing their portage tree, Gentoo users are able to use the most up to date packages available, rather than remaining fixed at a particular release date. This typically results in newer versions of software being available within the package manager than are available for other Linux distributions at any given time, particularly those which are fixed at a particular release (albeit with security updates). This is also a drawback; when updating a Gentoo system, no guarantees are made on the backwards-compatibility of any package updates, whereas distributions which only make a limited release set of packages available are able to better maintain compatibility within each release.

Slow package installation

Compiling from source means that some packages are slower to install. Slow package installation leads to a longer initial installation if a lot of packages are installed. In the extreme cases of KDE and OpenOffice.org, package installation will take hours,^[29][30] or even days on older hardware. Also compiling these packages requires a lot of disk space while the package is compiling (4–6 GB for OpenOffice.org – see app-office/openoffice ebuild for more information). Generally, Gentoo users accept these delays as the cost of being able to apply their own compile-time options, but there are now pre-compiled binaries for large popular applications such as KDE, OpenOffice.org, and Mozilla Firefox. Using these binaries one loses the chance to customize the choice of optional features for those packages, but the installation of the package is reduced to a few minutes.

The promise of optimisation

Gentoo has long been criticised for its alleged promise of faster program execution, as by design it allows the administrator to set compiler flags. Websites such as were expressly set up to satirise this "ricer" approach to computing. In reality, compiler optimisations rarely benefit execution of a program to such an extent that it warrants compiling an entire operating system and application software, instead of using precompiled packages as other (Linux) distributions normally do. Gentoo package management system does, however, offer options that allow users to install fewer (library) packages that applications would link to, which coul; Soft dependencies : Since packages are built by source, dependencies between packages are more flexible than for binary distributions, and can be exblicitly enabled or disabled in many cases. Binary distributions typically offer similar flexibility by providing several versions of the same package under different aliases, or by splitting packages into more modular components where possible. Since the number of possible configurations becomes combinatoric as the number of compile-time options increases, it is not feasible to store binaries for all possible combinations. Gentoo is thus able to offer a greater variety of compile-time package options where other popular distributions are not.d ultimately result in a leaner, smaller operating environment which would certainly execute (or at least start up) faster than any environment that has unwanted libraries linked in and more background services running unnecessarily.

Requires a good Internet connection

This seems to be related to downloading sources prior to building packages. However, any other distribution that has internet updates has to download binary packages instead, and the sizes of binary and source packages are usually comparable. Mitigating this drawback is that the necessary files can be pre-fetched with the emerge -f or --fetchonly flag, or they can be downloaded in the background while compiling by enabling the parallel-fetch feature.

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