Gentoo Linux ppc Manual: Trabalhando com o Gentoo

Bem Vindo ao Portage

O Portage é uma das mais notáveis inovações do Gentoo em gerenciamento de software. Com sua grande flexibilidade e enorme quantidade de recursos ele é visto frequentemente como a melhor ferramenta de gerenciamento de software disponível para Linux.

O Portage é inteiramente escrito em Python e Bash e assim é totalmente transparente aos usuários uma vez que ambas são linguagens de scripts.

A maioria dos usuários irá trabalhar com o Portage através da ferramenta emerge. Este capítulo não foi feito para duplicar as informações disponíveis na página de manual do emerge. Para uma lista completa das opções do emerge, por favor consulte a página do manual:

user $man emerge

Repositório Gentoo

Ebuilds

Quando a documentação do Gentoo falar sobre pacotes, isso significa títulos de software disponíveis aos usuários Gentoo através do repositório Gentoo. Esse repositório é uma coleção de ebuilds, arquivos que contém toda a informação que o Portage necessita para manter o software (instalar, procurar etc). Essas ebuilds residem em /var/db/repos/gentoo como padrão.

Quando alguém solicita ao Portage executar alguma ação em relação ao títulos de software, ele irá usar as ebuilds no sistema como base. É muito importante atualizar regularmente as ebuilds no sistema para que o Portage saiba sobre novo software, atualizações de segurança etc.

Atualizando o repositório Gentoo

O repositório Gentoo é normalmente atualizado com o rsync, um utilitário rápido de transferência incremental de arquivos. Atualizar é bastante simples já que o comando emerge provê um front-end para o rsync:

root #emerge --sync

Algumas vezes restrições de firewall impedem o rsync de contatar os espelhos. Neste caso, atualize o repositório Gentoo através de snapshots gerados diariamente. A ferramenta emerge-webrsync automaticamente baixa e instala o último snapshot no sistema:

root #emerge-webrsync

Mantendo software

Procurando por software

Há varias maneiras de se procurar software no repositório Gentoo. Uma delas e através do próprio emerge. Como padrão, emerge --search retorna os nomes do pacotes que os títulos correspondem (completa ou parcialmente) ao termo procurado.

Por exemplo, para procurar por todos os pacotes que têm "pdf" em seus nomes:

user $emerge --search pdf

Para pesquisar através das descrições também, use a opção --searchdesc (ou -S):

user $emerge --searchdesc pdf

Note que a saída retorna muita informação. Os campos são claramente descritos de modo que não iremos detalhar seus significados:

CODE Exemplo de saída para o comando search

*  net-print/cups-pdf
      Latest version available: 1.5.2
      Latest version installed: [ Not Installed ]
      Size of downloaded files: 15 kB
      Homepage:    http://cip.physik.uni-wuerzburg.de/~vrbehr/cups-pdf/
      Description: Provides a virtual printer for CUPS to produce PDF files.
      License:     GPL-2

Instalando software

Quando um título de software é encontrado, então a instalação necessita de apenas um comando emerge. Por exemplo, para instalar o gnumeric:

root #emerge --ask app-office/gnumeric

Uma vez que muitas aplicações dependem umas das outras, uma tentativa de instalar um certo pacote pode resultar na instalação de varias dependências também. Não se preocupe, o Portage cuida das dependências também. Para saber o que o Portage irá instalar, adicione a opção --pretend. Por exemplo:

root #emerge --pretend gnumeric

To do the same, but interactively choose whether or not to proceed with the installation, add the --ask flag:

root #emerge --ask gnumeric

Durante a instalação do pacote, o Portage irá baixar o código-fonte necessário da Internet (se necessário) e armazená-lo por default em /var/cache/distfiles/. Em seguida ele irá descompactar, compilar e instalar o pacote. Para dizer ao Portage para somente baixar os fontes sem instalá-los, adicione a opção --fetchonly ao comando emerge:

root #emerge --fetchonly gnumeric

Achando a documentação de um pacote instalado

Muitos pacotes vem com sua própria documentação. Algumas vezes, a USE flag doc determina se a documentação do pacote deve ser instalada ou não. Para ver se a USE flag doc é usada por um pacote, use emerge -vp category/package:

root #emerge -vp media-libs/alsa-lib

These are the packages that would be merged, in order:
[ebuild  R    ] media-libs/alsa-lib-1.1.3::gentoo USE="python -alisp -debug -doc" ABI_X86="(64) -32 (-x32)" PYTHON_TARGETS="python2_7" 0 KiB

A melhor maneira de habilitar a USE flag doc é fazendo para cada pacotes via /etc/portage/package.use, de modo que somente a documentação dos pacotes desejados é instalada. Para mais informação, por favor leia o seção USE flags.

Uma vez que o pacote esteja instalado, sua documentação é geralmente encontrada no subdiretório com o nome do pacote no diretório /usr/share/doc/:

user $ls -l /usr/share/doc/alsa-lib-1.1.3

total 16
-rw-r--r-- 1 root root 3098 Mar  9 15:36 asoundrc.txt.bz2
-rw-r--r-- 1 root root  672 Mar  9 15:36 ChangeLog.bz2
-rw-r--r-- 1 root root 1083 Mar  9 15:36 NOTES.bz2
-rw-r--r-- 1 root root  220 Mar  9 15:36 TODO.bz2

Uma forma mais confiável de listar os arquivos de documentação instalados é usar a opção --filter do equery. O equery é usado para consultar o banco de dados do Portage e faz parte do pacote app-portage/gentoolkit:

user $equery files --filter=doc alsa-lib

 * Searching for alsa-lib in media-libs ...
 * Contents of media-libs/alsa-lib-1.1.3:
/usr/share/doc/alsa-lib-1.1.3/ChangeLog.bz2
/usr/share/doc/alsa-lib-1.1.3/NOTES.bz2
/usr/share/doc/alsa-lib-1.1.3/TODO.bz2
/usr/share/doc/alsa-lib-1.1.3/asoundrc.txt.bz2

A opção --filter pode ser usada com outras regras para ver o local de instalação de muitos outros tipos de arquivos. Funcionalidades adicionais podem consultadas na página de manual do equery: man 1 equery.

Removendo software

Para remover software de um sistema, use emerge --unmerge. Isto irá dizer ao Portage para remover todos os arquivos instalados por este pacote do sistema. Uma exceção são os arquivos de configuração desta aplicação se eles foram alterados pelo usuário. Deixar os arquivos de configuração permite aos usuários continuar trabalhando com o pacote sem a necessidade de reconfiguração se os pacotes forem reinstalados mais tarde.

root #emerge --unmerge gnumeric

Quando um pacote é removido do sistema, as dependências deste pacote que foram instaladas automaticamente são deixadas no sistemas. Para que o Portage localize todas as dependências que podem agora ser removidas, use a funcionalidade do emerge code>--depclean, que será explicada mais tarde.

Atualizando o sistema

Para manter o sistema em perfeito estado (e sem mencionar com as últimas atualizações de segurança) é necessário atualizar o sistema regularmente. Uma vez que o Portage somente checa as ebuilds no repositório Gentoo, a primeira coisa a fazer é atualizar esse repositório. Quando o repositório Gentoo é atualizado, o sistema pode ser atualizado usando emerge --update @world. No próximo exemplo, a opção --ask é usada também para que o Portage mostre a lista de pacotes que serão atualizados e espere uma confirmação:

O Portage irá então procurar por novas versões dos aplicativos que estão instalados. Contudo, ele irá somente verificar as versões dos aplicativos que estão explicitamente instaladas (as aplicações listadas em /var/lib/portage/world) - ele não irá checar suas dependências. Para atualizar as dependências destes pacotes também, adicione a opção --deep:

root #emerge --update --deep @world

Se as configurações USE do sistemas foram alteradas, é recomendado adicionar --newuse também. O Portage irá verificar se a alteração requer a instalação de novos pacotes ou a recompilação dos existentes:

root #emerge --update --deep --with-bdeps=y --newuse @world

Metapacotes

Alguns pacotes no repositório do Gentoo não tem nenhum conteúdo real mas são usados para instalar uma coleção de pacotes. Por exemplo, o pacote kde-plasma/plasma-meta irá instalar o desktop KDE Plasma completo no sistema baixando os vários pacotes relacionados ao Plasma e sua dependências.

Para remover esse pacote de seu sistema, executar emerge --unmerge no pacote não tem muito efeito já que suas dependências ficarão no sistema.

O Portage tem a funcionalidade de remover também dependências órfãs, mas uma vez a disponibilidade de software é dinamicamente dependente, é importante primeiro atualizar completamente o sistema, incluindo as novas alterações nas USE flags. Feito isso pode-se executar emerge --depclean para remover as dependências órfãs. Quando concluído, pode ser necessário recompilar as aplicações que foram linkadas dinamicamente aos agora removidos softwares mas não os requerem mais, suporte recente para isto foi adicionado ao Portage.

Tudo isso é feito com os três seguintes comandos:

root #emerge --update --deep --newuse @world

root #emerge --depclean

root #revdep-rebuild

Licenças

A partir do Portage versão 2.1.7, é possível aceitar ou rejeitar a instalação de software baseado em sua licença. Todos os pacotes na árvore contém uma LICENSE em suas ebuilds. Executando emerge --search package/category irá mostrar a licença do pacote.

Importante
A variável LICENSE em uma ebuild é apenas uma indicação para os desenvolvedores e usuários do Gentoo. Ela não tem valor legal e não há garantias de que reflita a realidade. Desse modo, não confie cegamente nela, mas cheque o pacote em si cuidadosamente, incluindo todos os arquivos que usar.

If a discrepancy is found in the ebuild, please file a bug to suggest a change to the value(s) assigned to the ebuild's LICENSE variable.}}

Como padrão, o Portage permite as licenças que são explicitamente aprovadas pela Free Software Foundation, pela Open Source Initiative, ou que seguem a Free Software Definition.

A variável que controla as licenças permitidas é chamada ACCEPT_LICENSE, que pode ser configurada no arquivo /etc/portage/make.conf. No próximo exemplo, seu valor padrão é mostrado:

FILE /etc/portage/make.confA configuração ACCEPT_LICENSE padrão

ACCEPT_LICENSE="-* @FREE"

Com esta configuração, os pacotes de software ou documentação com uma licença livre serão instaláveis. Softwares não livres não serão instaláveis.

É possível configurar ACCEPT_LICENSE globalmente no /etc/portage/make.conf, ou especificá-la por pacote no arquivo /etc/portage/package.license.

Por exemplo, para permitir a licença google-chrome para o pacote www-client/google-chrome, adicione o seguinte em /etc/portage/package.license:

FILE /etc/portage/package.licenseAceitando a licença google-chrome para o pacote google-chrome

www-client/google-chrome google-chrome

Isto permite a instalação do pacote www-client/google-chrome, mas proíbe a instalação do pacote www-plugins/chrome-binary-plugins, mesmo que eles tenham a mesma licença.

Or to allow the often-needed sys-kernel/linux-firmware:

FILE /etc/portage/package.licenseAccepting the licenses for the linux-firmware package

# Accepting the license for linux-firmware
sys-kernel/linux-firmware linux-fw-redistributable
</div>

<div lang="en" dir="ltr" class="mw-content-ltr">
# Accepting any license that permits redistribution
sys-kernel/linux-firmware @BINARY-REDISTRIBUTABLE

Importante
Licenças são guardadas no diretório /var/db/repos/gentoo/licenses/, e grupos de licenças são mantidas no arquivo /var/db/repos/gentoo/profiles/license_groups. A primeira entrada de cada linha em MAIÚSCULAS é o nome do grupo de licenças, e cada entrada depois dessa é uma licença individual.

Grupos de licença definidos na variável ACCEPT_LICENSE são prefixadas com um sinal @. Uma configuração possível (que era o default antigo do Portage) é permitir todas as licenças, exceto End User License Agreements (EULAs) que requerem a leitura e aceitação de um termo de aceitação. Para conseguir isso, aceite todas as licenças (usando *) e então remova as licenças do grupo EULA, como abaixo:

FILE /etc/portage/make.confAceite todas as licenças exceto EULAs

ACCEPT_LICENSE="* -@EULA"

Note que essa configuração irá aceitar também software e documentação não livres.

Quando o Portage reclamar

Terminologia

Como dito antes, o Portage é extremamente poderoso e suporta muitas funções que outros gerenciadores de software não tem. Para entender isto, explicaremos uns poucos aspectos do Portage sem entrar em muitos detalhes.

Com o Portage diferentes versões de um mesmo pacote podem coexistir em um sistema. Enquanto outras distribuições tendem a dar nomes em seus pacotes para essas versões (como freetype e freetype2) o Portage usa uma terminologia chamada "SLOT". Um ebuild declara um certo SLOT para sua versão. Ebuilds com diferentes SLOTs podem coexistir em um mesmo sistema. Por exemplo, o pacote freetype tem ebuilds com SLOT="1" e SLOT="2".

Há também pacotes que proveem a mesma funcionalidade mas são implementados de forma diferente. Por exemplo, metalogd, sysklogd, e syslog-ng são todos sistemas de log. Aplicações que para sua disponibilidade precisam de um "sistema de log" não podem depender, por exemplo, do metalogd, se há outras opções de sistemas de log. O Portage permite virtuais: cada sistema de log é listado com uma "exclusiva" dependência de um serviço de log em um pacote virtual de uma categoria virtual, então estas aplicação pode depender do pacote virtual/logger. Quando instalado, o pacote irá baixar o primeiro pacote de log mencionado neste pacote, a não ser que um pacote de log já esteja instalado (neste caso a virtual já foi satisfeita).

Software no repositório Gentoo pode residir em diferentes ramos. Como padrão o sistema somente aceita pacotes que o Gentoo considera estáveis. Muitos títulos de software novos, quando enviados, são adicionados ao ramo de teste, significando que mais testes são necessários antes que ele seja marcado como estável. Mesmo que os ebuilds deste software esteja no repositório Gentoo, o Portage não irá atualizá-los se eles não forem colocados no ramo estável.

Alguns softwares estão disponíveis somente para umas poucas arquiteturas, ou precisam de mais testes, ou o desenvolvedor que enviou o software para o repositório Gentoo não conseguiu verificar se o pacote trabalha em uma arquitetura diferente.

Cada instalação do Gentoo adere a um certo perfil que contém, além de outras informações, a lista de pacotes que são requeridos para o sistema funcionar normalmente.

Pacotes bloqueados

CODE Portage avisando sobre pacotes bloqueados (com --pretend)

[blocks B     ] mail-mta/ssmtp (is blocking mail-mta/postfix-2.2.2-r1)

• Error: The above package list contains packages which cannot be

* installed at the same time on the same system.

(x11-wm/i3-4.20.1:0/0::gentoo, ebuild scheduled for merge) pulled in by

   x11-wm/i3

Ebuilds contem campos específicos que informam ao Portage sobre suas dependências. Há duas dependências possíveis: dependências de build, declaradas na variável DEPEND e dependências de execução, declaradas em RDEPEND. Quando uma dessas dependências indica explicitamente que um pacotes ou virtual não e compatível, um bloqueio é disparado.

Enquanto versões recentes do Portage são inteligentes o bastante para resolver bloqueios menores sem intervenção do usuário, ocasionalmente alguns bloqueios precisam ser resolvidos manualmente.

Para corrigir um bloqueio, usuários podem escolher não instalar o pacote ou fazer unmerge do pacore conflitante primeiro. Neste exemplo, podemos optar por não instalar o postfix ou remover o ssmtp primeiro.

Algumas vezes há também pacotes bloqueados com versões específicas, como <media-video/mplayer-1.0_rc1-r2. Neste caso, atualizar para uma versão mais recente do pacote pode remover o bloqueio.

É possível também que dois pacotes que estão para ser instalados bloqueiem um ao outro. Nesses casos raros, tente achar porque ambos precisam ser instalados. Na maioria dos casos apenas um deles é suficiente. Se não, por favor crie um bug no sistema de acompanhamento de bugs do Gentoo.

Pacotes mascarados

CODE Portage avisando sobre pacotes mascarados

!!! all ebuilds that could satisfy "bootsplash" have been masked.

CODE Portage avisando sobre pacotes mascarados - razão

!!! possible candidates are:
  
- gnome-base/gnome-2.8.0_pre1 (masked by: ~x86 keyword)
- lm-sensors/lm-sensors-2.8.7 (masked by: -sparc keyword)
- sys-libs/glibc-2.3.4.20040808 (masked by: -* keyword)
- dev-util/cvsd-1.0.2 (masked by: missing keyword)
- games-fps/unreal-tournament-451 (masked by: package.mask)
- sys-libs/glibc-2.3.2-r11 (masked by: profile)
- net-im/skype-2.1.0.81 (masked by: skype-eula license(s))

Quando tentar instalar um pacote que não está disponível para o sistema, este erro de mascaramento ocorre. Usuários devem tentar instalar uma aplicação diferente que esteja disponível para o sistema ou esperar até o pacote ser marcado como disponível. Há sempre uma razão porque o pacote é mascarado:

Razões para mascaramento	Descrição
palavra chave ~arch	A aplicação não foi testada o suficiente para ser colocada no ramo estável. Espere uns dias ou semanas e tente novamente.
palavra chave -arch ou -*	A aplicação não funciona em sua arquitetura. Se você acredita que o pacote funciona coloque um bug em nosso site Bugzilla.
palavra chave missing	A aplicação não foi testada em sua arquitetura ainda. Pergunte ao time de arquitetura se eles podem testar o pacote ou teste para eles e faça um relatório em nosso site Bugzilla.
package.mask	O pacote está corrompido, instável ou pior, foi deliberadamente marcado como inútil.
profile	O pacote encontrado não é adequado ao perfil atual. A aplicação pode quebrar o sistema se instalada ou não é compatível com o perfil atualmente usado.
license	A licença do pacote não é compatível com o valor ACCEPT_LICENSE. Habilite esta licença ou seu grupo configurando em /etc/portage/make.conf ou em /etc/portage/package.license

Mudanças necessárias nas USE flags

CODE Portage avisando sobre a necessidade de alteração na USE flag

The following USE changes are necessary to proceed:
#required by app-text/happypackage-2.0, required by happypackage (argument)
>=app-text/feelings-1.0.0 test

A mensagem de erro pode também ser mostrada como segue, se --autounmask não estiver habilitado:

CODE Erro do Portage sobre a necessidade de alteração na USE flag

emerge: there are no ebuilds built with USE flags to satisfy "app-text/feelings[test]".
!!! One of the following packages is required to complete your request:
- app-text/feelings-1.0.0 (Change USE: +test)
(dependency required by "app-text/happypackage-2.0" [ebuild])
(dependency required by "happypackage" [argument])

Este aviso ou erro ocorre quando um pacote é requerido para instalação ao qual não depende de outro pacote, mas este pacote requer um USE flag em particular para compilação (o conjunto de USE flags). No exemplo dado, o pacote app-text/feelings precisa ser compilado com USE="test", mas esta USE flags não está habilitada no sistema.

Para resolver isso, adicione a USE flag requerida para as USE flags globais em /etc/portage/make.conf, ou habilite para um pacote específico em /etc/portage/package.use.

Dependências faltantes

CODE Portage avisando sobre dependências faltantes

emerge: there are no ebuilds to satisfy ">=sys-devel/gcc-3.4.2-r4".
  
!!! Problem with ebuild sys-devel/gcc-3.4.2-r2
!!! Possibly a DEPEND/*DEPEND problem.

A aplicação a ser instalada depende de outro pacote que não está disponível para o sistema. Por favor cheque no Bugzilla se o problema é conhecido e se não, por favor faça um relatório. A não se que o sistema esteja configurado para mais de um ramo isto não deve ocorrer e provavelmente é um bug.

Nome do ebuild ambíguo

CODE O Portage avisando sobre nomes de ebuild ambíguos

[ Results for search key : listen ]
[ Applications found : 2 ]
  
*  dev-tinyos/listen [ Masked ]
      Latest version available: 1.1.15
      Latest version installed: [ Not Installed ]
      Size of files: 10,032 kB
      Homepage:      http://www.tinyos.net/
      Description:   Raw listen for TinyOS
      License:       BSD
  
*  media-sound/listen [ Masked ]
      Latest version available: 0.6.3
      Latest version installed: [ Not Installed ]
      Size of files: 859 kB
      Homepage:      http://www.listen-project.org
      Description:   A Music player and management for GNOME
      License:       GPL-2
  
!!! The short ebuild name "listen" is ambiguous. Please specify
!!! one of the above fully-qualified ebuild names instead.

A aplicação selecionada para instalação tem seu nome que corresponde a mais de um pacote. Forneça também a nome da categoria para resolver isso. O Portage irá informar o usuário sobre as possíveis opções a escolher.

Dependências circulares

CODE Portage avisando sobre dependência circular

!!! Error: circular dependencies: 
  
ebuild / net-print/cups-1.1.15-r2 depends on ebuild / app-text/ghostscript-7.05.3-r1
ebuild / app-text/ghostscript-7.05.3-r1 depends on ebuild / net-print/cups-1.1.15-r2

Dois (ou mais) pacotes a instalar dependem um do outro e não podem ser instalados. Isso é na maioria da vezes um bug em um dos pacotes do repositório Gentoo. Por favor sincronize novamente e tente mais tarde. Pode ser bom checar o Bugzilla para ver se o problema é conhecido e, se não, fazer um relatório dele.

Falha ao baixar

CODE Portage avisando sobre falha ao baixar

!!! Fetch failed for sys-libs/ncurses-5.4-r5, continuing...
(...)
!!! Some fetch errors were encountered.  Please see above for details.

O Portage não conseguiu fazer o download dos fontes da aplicação e irá tentar continuar instalando outras aplicações (se aplicável). Esta falha pode acontecer devido um espelho não estar sincronizado corretamente ou por causa de um ebuild apontar para um local incorreto. O servidor onde os fontes residem podem também estar fora do ar por alguma razão.

Tente novamente em uma hora para ver se o problema ainda persiste.

Proteção do perfil do sistema

CODE Portage avisando sobre um pacote protegido pelo perfil

!!! Trying to unmerge package(s) in system profile. 'sys-apps/portage'
!!! This could be damaging to your system.

O usuário tentou remover um pacote que é parte do núcleo de pacotes do sistema. Ele é listado como requerido pelo perfil e não deve ser removido do sistema.

Falha na verificação do resumo

CODE Falha na verificação do resumo

>>> checking ebuild checksums
!!! Digest verification failed:

Isto é um sinal que algo está errado com repositório Gentoo - frequentemente por causa de um desenvolvedor ter cometido algum erro quando no envio de um ebuild para o repositório de ebuilds do Gentoo.

Quando uma verificação de resumo falhar, não tente refazer o resumo novamente do pacote pessoalmente. Executar ebuild foo manifest não irá corrigir o problema; irá muito provavelmente fazê-lo pior!

Em vez disso, espere um hora ou duas até o repositório se estabilizar. É provável que o erro foi notado de imediato, mas pode levar um tempo para a correção chegar até os espelhos rsync. Cheque o Bugzilla e veja se alguém já reportou o problema ou pergunte no #gentoo (webchat) (IRC). Se não, vá em frente e abra um bug para o ebuild com problema.

Uma vez que o bug foi corrigido, sincronize novamente o repositório de ebuild do Gentoo para obter o resumo corrigido.

Importante
Tenha cuidado para não sincronizar o repositório de ebuild do Gentoo mais de uma vez ao dia. Como declarado na política de etiqueta oficial do Gentoo (assim como quando executamos o emerge --sync), usuários que sincronizarem muito frequentemente serão barrados de sincronizar por um tempo. Usuários que repetidamente violarem essa política podem ser banidos. A menos que absolutamente necessário, é melhor esperar um período de 24 horas para sincronizar de modo que a ressincronização não sobrecarregue os espelhos rsync do Gentoo.

O que são as flags USE

A ideia por trás das flags USE

When installing Gentoo, users make choices depending on the environment they are working with. A setup for a server differs from a setup for a workstation. A gaming workstation differs from a 3D rendering workstation.

This is not only true for choosing what packages to install, but also what features a certain package should support. If there is no need for OpenGL, why would someone bother to install and maintain OpenGL and build OpenGL support in most of the packages? If someone doesn't want to use KDE, why would they bother compiling packages with KDE support if those packages work flawlessly without?

To help users in deciding what to install/activate and what not, Gentoo wanted the user to specify his/her environment in an easy way. This forces the user into deciding what they really want and eases the process for Portage to make useful decisions.

Definition of a USE flag

Enter USE flags. Such a flag is a keyword that embodies support and dependency-information for a certain concept. If a certain USE flag is set to enabled, then Portage will know the system administrator desires support for the chosen keyword. Of course this may alter the dependency information for a package. Depending on the USE flag, this may require pulling in many more dependencies in order to fulfill the requested dependency changes.

Take a look at a specific example: the kde USE flag. If this flag is not set in the USE variable (or if the value is prefixed with a minus sign: -kde), then all packages that have optional KDE support will be compiled without KDE support. All packages that have an optional KDE dependency will be installed without installing the KDE libraries (as dependency).

When the kde flag is set to enabled, then those packages will be compiled with KDE support, and the KDE libraries will be installed as dependency.

By correctly defining USE flags, the system will be tailored specifically to the needs of the system administrator.

Using USE flags

Declare permanent USE flags

All USE flags are declared inside the USE variable. To make it easy for users to search and pick USE flags, we already provide a default USE setting. This setting is a collection of USE flags we think are commonly used by the Gentoo users. This default setting is declared in the make.defaults files that are part of the selected profile.

The profile the system listens to is pointed to by the /etc/portage/make.profile symlink. Each profile works on top of other profiles, and the end result is therefore the sum of all profiles. The top profile is the base profile (/var/db/repos/gentoo/profiles/base).

To view the currently active USE flags (completely), use emerge --info:

root #emerge --info | grep ^USE

USE="a52 aac acpi alsa branding cairo cdr dbus dts ..."

This variable already contains quite a lot of keywords. Do not alter any make.defaults file to tailor the USE variable to personal needs though: changes in these files will be undone when the Gentoo repository is updated!

To change this default setting, add or remove keywords to/from the USE variable. This is done globally by defining the USE variable in /etc/portage/make.conf. In this variable one can add the extra USE flags required, or remove the USE flags that are no longer needed. This latter is done by prefixing the keyword with the minus-sign (-).

For instance, to remove support for KDE and Qt but add support for LDAP, the following USE can be defined in /etc/portage/make.conf:

FILE /etc/portage/make.confUpdating USE in make.conf

USE="-kde -qt5 ldap"

Declaring USE flags for individual packages

Sometimes users want to declare a certain USE flag for one (or a couple) of applications but not system-wide. To accomplish this, edit /etc/portage/package.use. package.use is typically a single file, however it can also be a directory filled with children files; see the tip below and then man 5 portage for more information on how to use this convention. The following examples assume package.use is a single file.

For instance, to only have Blu-ray support for the VLC media player package:

FILE /etc/portage/package.useEnabling Blu-ray support for VLC

media-video/vlc bluray

Dica
If package.use is pre-existing as a directory (opposed to a single file), packages can have their USE flags modified by simply creating files under the package.use/ directory. Any file naming convention can work, however it is wise to implement a coherent naming scheme. One convention is to simply use the package name as the title for the child file. For example, setting the bluray USE flag for the media-video/vlc package can be performed as follows:

root #echo "media-video/vlc bluray" >> /etc/portage/package.use/vlc

Similarly it is possible to explicitly disable USE flags for a certain application. For instance, to disable bzip2 support in PHP (but have it for all other packages through the USE flag declaration in make.conf):

FILE /etc/portage/package.useDisable bzip2 support for PHP

dev-lang/php -bzip2

Declaring temporary USE flags

Sometimes users need to set a USE flag for a brief moment. Instead of editing /etc/portage/make.conf twice (to do and undo the USE changes) just declare the USE variable as an environment variable. Remember that this setting only applies for the command entered; re-emerging or updating this application (either explicitly or as part of a system update) will undo the changes that were triggered through the (temporary) USE flag definition.

The following example temporarily removes the pulseaudio value from the USE variable during the installation of SeaMonkey:

root #USE="-pulseaudio" emerge www-client/seamonkey

Precedence

Of course there is a certain precedence on what setting has priority over the USE setting. The precedence for the USE setting is, ordered by priority (first has lowest priority):

1. Default USE setting declared in the make.defaults files part of your profile
2. User-defined USE setting in /etc/portage/make.conf
3. User-defined USE setting in /etc/portage/package.use
4. User-defined USE setting as environment variable

To view the final USE setting as seen by Portage, run emerge --info. This will list all relevant variables (including the USE variable) with their current definition as known to Portage.

root #emerge --info

Adapting the entire system to the new USE flags

After having altered USE flags, the system should be updated to reflect the necessary changes. To do so, use the --newuse option with emerge:

root #emerge --update --deep --newuse @world

Next, run Portage's depclean to remove the conditional dependencies that were emerged on the "old" system but that have been obsoleted by the new USE flags.

Importante
Double-check the provided list of "obsoleted" packages to make sure it does not remove packages that are needed. In the following example, add the --pretend (-p) switch to have depclean only list the packages without removing them:

root #emerge --pretend --depclean

When depclean has finished, emerge may prompt to rebuild the applications that are dynamically linked against shared objects provided by possibly removed packages. Portage will preserve necessary libraries until this action is done to prevent breaking applications. It stores what needs to be rebuilt in the preserved-rebuild set. To rebuild the necessary packages, run:

root #emerge @preserved-rebuild

When all this is accomplished, the system is using the new USE flag settings.

Package specific USE flags

Viewing available USE flags

Let's take the example of seamonkey: what USE flags does it listen to? To find out, we use emerge with the --pretend and --verbose options:

root #emerge --pretend --verbose www-client/seamonkey

These are the packages that would be merged, in order:
 
Calculating dependencies... done!
[ebuild  N     ] www-client/seamonkey-2.48_beta1::gentoo  USE="calendar chatzilla crypt dbus gmp-autoupdate ipc jemalloc pulseaudio roaming skia startup-notification -custom-cflags -custom-optimization -debug -gtk3 -jack -minimal (-neon) (-selinux) (-system-cairo) -system-harfbuzz -system-icu -system-jpeg -system-libevent -system-libvpx -system-sqlite {-test} -wifi" L10N="-ca -cs -de -en-GB -es-AR -es-ES -fi -fr -gl -hu -it -ja -lt -nb -nl -pl -pt-PT -ru -sk -sv -tr -uk -zh-CN -zh-TW" 216,860 KiB
 
Total: 1 package (1 new), Size of downloads: 216,860 KiB

emerge isn't the only tool for this job. In fact, there is a tool dedicated to package information called equery which resides in the app-portage/gentoolkit package

root #emerge --ask app-portage/gentoolkit

Now run equery with the uses argument to view the USE flags of a certain package. For instance, for the app-portage/portage-utils package:

user $equery --nocolor uses =app-portage/portage-utils-0.93.3

[ Legend : U - final flag setting for installation]
[        : I - package is installed with flag     ]
[ Colors : set, unset                             ]
 * Found these USE flags for app-portage/portage-utils-0.93.3:
 U I
 + + nls       : Add Native Language Support (using gettext - GNU locale utilities)
 + + openmp    : Build support for the OpenMP (support parallel computing), requires >=sys-devel/gcc-4.2 built with USE="openmp"
 + + qmanifest : Build qmanifest applet, this adds additional dependencies for GPG, OpenSSL and BLAKE2B hashing
 + + qtegrity  : Build qtegrity applet, this adds additional dependencies for OpenSSL
 - - static    : !!do not set this during bootstrap!! Causes binaries to be statically linked instead of dynamically

Satisfying REQUIRED_USE conditions

Some ebuilds require or forbid certain combinations of USE flags in order to work properly. This is expressed via a set of conditions placed in a REQUIRED_USE expression. This conditions ensure that all features and dependencies are complete and that the build will succeed and perform as expected. If any of these are not met, emerge will alert you and ask you to fix the issue.

Example	Description
REQUIRED_USE="foo? ( bar )"	If foo is set, bar must be set.
REQUIRED_USE="foo? ( !bar )"	If foo is set, bar must not be set.
REQUIRED_USE="foo? ( || ( bar baz ) )"	If foo is set, bar or baz must be set.
REQUIRED_USE="^^ ( foo bar baz )"	Exactly one of foo bar or baz must be set.
REQUIRED_USE="|| ( foo bar baz )"	At least one of foo bar or baz must be set.
REQUIRED_USE="?? ( foo bar baz )"	No more than one of foo bar or baz may be set.

Recursos do portage

O portage tem vários recursos adicionais que faz a experiência com o Gentoo ainda melhor. Muitos desses recursos dependem de ferramentas de software que melhoram o desempenho, confiabilidade, segurança, ...

To enable or disable certain Portage features, edit /etc/portage/make.conf and update or set the FEATURES variable which contains the various feature keywords, separated by white space. In several cases it will also be necessary to install the additional tool on which the feature relies.

Not all features that Portage supports are listed here. For a full overview, please consult the make.conf man page:

user $man make.conf

To find out what FEATURES are set by default, run emerge --info and search for the FEATURES variable or grep it out:

user $emerge --info | grep ^FEATURES=

Distributed compiling

Usando o distcc

distcc is a program to distribute compilations across several, not necessarily identical, machines on a network. The distcc client sends all necessary information to the available distcc servers (running distccd) so they can compile pieces of source code for the client. The net result is a faster compilation time.

Maiores informações sobre o distcc (e como fazê-lo funcionar com o Gentoo) podem ser encontradas no artigo do Distcc.

Instalando o distcc

O distcc contém um monitor gráfico para monitorar as tarefas que estão sendo enviadas para compilação. Essa ferramenta é instalada automaticamente se USE=gnome ou USE=gtk estiver habilitada.

root #emerge --ask sys-devel/distcc

Ativando o suporte do Portage ao distcc

Add distcc to the FEATURES variable inside /etc/portage/make.conf. Next, edit the MAKEOPTS variable and increase the number of parallel build jobs that the system allows. A known guideline is to fill in -jN where N is the number of CPUs that run distccd (including the current host) plus one, but that is just a guideline.

Now run distcc-config and enter the list of available distcc servers. For a simple example assume that the available DistCC servers are 192.168.1.102 (the current host), 192.168.1.103 and 192.168.1.104 (two "remote" hosts):

root #distcc-config --set-hosts "192.168.1.102 192.168.1.103 192.168.1.104"

Não se esqueça de executar também o daemon distcc:

root #rc-update add distccd default

root #/etc/init.d/distccd start

Caching compilation objects

Sobre o ccache

ccache is a fast compiler cache. Whenever an application is compiled, it will cache intermediate results so that, whenever the same program and version is recompiled, the compilation time is greatly reduced. The first time ccache is run, it will be much slower than a normal compilation. Subsequent recompiles however should be faster. ccache is only helpful if the same application version will be recompiled many times; thus it is mostly only useful for software developers.

Para maiores informações sobre o ccache, por favor visite sua homepage.

Aviso
ccache is known to cause numerous compilation failures. Sometimes ccache will retain stale code objects or corrupted files, which can lead to packages that cannot be emerged. If this happens (errors like "File not recognized: File truncated" come up in build logs), try recompiling the application with ccache disabled (FEATURES="-ccache" in /etc/portage/make.conf or one-shot from the commandline with the following) before reporting a bug:

root #FEATURES="-ccache" emerge --oneshot <category/package>

Instalando o ccache

To install ccache run the following command:

root #emerge --ask dev-util/ccache

Activating Portage ccache support

Open /etc/portage/make.conf and add ccache to any values defined in the FEATURES variable. If FEATURES does not exist, then create it. Next, add a new variable called CCACHE_SIZE and set it to 2G:

FILE /etc/portage/make.confEnabling Portage ccache support

FEATURES="ccache"
CCACHE_SIZE="2G"

To check if ccache functions, ask ccache to provide its statistics. Because Portage uses a different ccache home directory, it is necessary to temporarily set the CCACHE_DIR variable:

root #CCACHE_DIR="/var/tmp/ccache" ccache -s

The /var/tmp/ccache/ location is Portage' default ccache home directory; it can be changed by setting the CCACHE_DIR variable in /etc/portage/make.conf.

When running ccache standalone, it would use the default location of ${HOME}/.ccache/, which is why the CCACHE_DIR variable needs to be set when asking for the (Portage) ccache statistics.

Using ccache outside Portage

To use ccache for non-Portage compilations, add /usr/lib/ccache/bin/ to the beginning of the PATH variable (before /usr/bin). This can be accomplished by editing ~/.bash_profile in the user's home directory. Using ~/.bash_profile is one way to define PATH variables.

FILE ~/.bash_profileSetting the ccache location before any other PATH

PATH="/usr/lib/ccache/bin:${PATH}"

Binary package support

Creating prebuilt packages

Portage supports the installation of prebuilt packages.

To create a prebuilt package use the quickpkg command if the package is already installed on the system, or emerge with the --buildpkg or --buildpkgonly options.

To have Portage create prebuilt packages of every single package that gets installed, add buildpkg to the FEATURES variable.

More extended support for creating prebuilt package sets can be obtained with catalyst. For more information on catalyst please read the Catalyst FAQ.

Installing prebuilt packages

Although Gentoo doesn't provide one, it is possible to create a central repository where prebuilt packages are stored. In order to use this repository, it is necessary to make Portage aware of it by having the PORTAGE_BINHOST variable point to it. For instance, if the prebuilt packages are on ftp://buildhost/gentoo:

FILE /etc/portage/make.confAdd PORTAGE_BINHOST location

PORTAGE_BINHOST="ftp://buildhost/gentoo"

To install a prebuilt package, add the --getbinpkg option to the emerge command alongside of the --usepkg option. The former tells emerge to download the prebuilt package from the previously defined server while the latter asks emerge to try to install the prebuilt package first before fetching the sources and compiling it.

For instance, to install gnumeric with prebuilt packages:

root #emerge --usepkg --getbinpkg gnumeric

More information about emerge's prebuilt package options can be found in the emerge man page:

user $man emerge

Distributing prebuilt packages to others

If prebuilt packages are to be distributed to others, then make sure that this is permitted. Check the distribution terms of the upstream package for this. For example, for a package released under the GNU GPL, sources must be made available along with the binaries.

Ebuilds may define a bindist restriction in their RESTRICT variable if built binaries are not distributable. Sometimes this restriction is conditional on one or more USE flags.

By default, Portage will not mask any packages because of restrictions. This can be changed globally by setting the ACCEPT_RESTRICT variable in /etc/portage/make.conf. For example, to mask packages that have a bindist restriction, add the following line to make.conf:

FILE /etc/portage/make.confOnly accept binary distributable packages

ACCEPT_RESTRICT="* -bindist"

It is also possible to override the ACCEPT_RESTRICT variable by passing the --accept-restrict option to the emerge command. For example, --accept-restrict=-bindist will temporarily mask packages with a bindist restriction.

Also consider setting the ACCEPT_LICENSE variable when distributing packages. See the Licenses section for this.

Importante
It is entirely the responsibility of each user to comply with packages' license terms and with laws of each user's country. The metadata variables defined by ebuilds (RESTRICT or LICENSE) can provide guidance when distribution of binaries is not permitted, however output from Portage or questions answered by the Gentoo developers are not legal statements and should not be relied upon as such. Be cautious to abide by the law of your physical location.

Fetching files

Verify distfiles

To re-verify the integrity and (potentially) re-download previously removed/corrupted distfiles for all currently installed packages, run:

root #emerge --ask --fetchonly --emptytree @world

Importante
The contents of this page do not apply to users that chose a systemd profile in Choosing the right profile.

Runlevels

Inicializando o sistema

Quando o sistema é inicializado, um monte de texto passa "voando". Prestando bastante atenção, irá-se notar que o texto é (normalmente) o mesmo sempre que o sistema é inicializado. A sequência de todas as ações é chamada de sequência de boot e é (mais ou menos) definida estaticamente.

Primeiro, o carregador de boot carrega a imagem do kernel que está definida na configuração do carregador de boot. Depois, o carregador de boot instrui a CPU para executar o kernel. Quando o kernel é carregado e executado, ele inicializa todas as estruturas e tarefas específicas do kernel e inicia o processo init.

O processo então se certifica que todos os sistemas de arquivos (definidos em /etc/fstab) são montados e prontos para uso. Então ele executa diversos scripts localizados em /etc/init.d/, que irá inicializar os serviços necessários de modo a se ter um sistema corretamente inicializado.

Por fim, quando todos os scripts terminaram de executar, o init ativa os terminais (normalmente são apenas os consoles virtuais ativados pelas teclas Alt+F1, Alt+F2, etc.), anexando um processo especial chamado agetty a eles. Esse processo então certifica-se os usuários são capazes de logar por esses terminais executando o login.

Scripts de inicialização

O init não executa os scripts em /etc/init.d/ aleatoriamente. Nem mesmo ele executa todos os scripts em /etc/init.d/, apenas os scripts que devem ser executados. Ele decide quais scripts executar consultando em /etc/runlevels/.

First, init runs all scripts from /etc/init.d/ that have symbolic links inside /etc/runlevels/boot/. Usually, it will start the scripts in alphabetical order, but some scripts have dependency information in them, telling the system that another script must be run before they can be started.

When all /etc/runlevels/boot/ referenced scripts are executed, init continues with running the scripts that have a symbolic link to them in /etc/runlevels/default/. Again, it will use the alphabetical order to decide what script to run first, unless a script has dependency information in it, in which case the order is changed to provide a valid start-up sequence. The latter is also the reason why commands used during the installation of Gentoo Linux used default, as in rc-update add sshd default.

Com funciona o init

Of course init doesn't decide all that by itself. It needs a configuration file that specifies what actions need to be taken. This configuration file is /etc/inittab.

Remember the boot sequence that was just described - init's first action is to mount all file systems. This is defined in the following line from /etc/inittab:

FILE /etc/inittabInitialization command

si::sysinit:/sbin/openrc sysinit

This line tells init that it must run /sbin/openrc sysinit to initialize the system. The /sbin/openrc script takes care of the initialization, so one might say that init doesn't do much - it delegates the task of initializing the system to another process.

Second, init executed all scripts that had symbolic links in /etc/runlevels/boot/. This is defined in the following line:

FILE /etc/inittabBoot command invocation

rc::bootwait:/sbin/openrc boot

Again the OpenRC script performs the necessary tasks. Note that the option given to OpenRC (boot) is the same as the sub-directory of /etc/runlevels/ that is used.

Now init checks its configuration file to see what runlevel it should run. To decide this, it reads the following line from /etc/inittab:

FILE /etc/inittabDefault runlevel selection

id:3:initdefault:

In this case (which the majority of Gentoo users will use), the runlevel id is 3. Using this information, init checks what it must run to start runlevel 3:

FILE /etc/inittabRunlevel definitions

l0:0:wait:/sbin/openrc shutdown
l1:S1:wait:/sbin/openrc single
l2:2:wait:/sbin/openrc nonetwork
l3:3:wait:/sbin/openrc default
l4:4:wait:/sbin/openrc default
l5:5:wait:/sbin/openrc default
l6:6:wait:/sbin/openrc reboot

The line that defines level 3, again, uses the openrc script to start the services (now with argument default). Again note that the argument of openrc is the same as the subdirectory from /etc/runlevels/.

When OpenRC has finished, init decides what virtual consoles it should activate and what commands need to be run at each console:

FILE /etc/inittabTerminal definitions

c1:12345:respawn:/sbin/agetty 38400 tty1 linux
c2:12345:respawn:/sbin/agetty 38400 tty2 linux
c3:12345:respawn:/sbin/agetty 38400 tty3 linux
c4:12345:respawn:/sbin/agetty 38400 tty4 linux
c5:12345:respawn:/sbin/agetty 38400 tty5 linux
c6:12345:respawn:/sbin/agetty 38400 tty6 linux

Available runlevels

In a previous section, we saw that init uses a numbering scheme to decide what runlevel it should activate. A runlevel is a state in which the system is running and contains a collection of scripts (runlevel scripts or initscripts) that must be executed when entering or leaving a runlevel.

In Gentoo, there are seven runlevels defined: three internal runlevels, and four user-defined runlevels. The internal runlevels are called sysinit, shutdown and reboot and do exactly what their names imply: initialize the system, powering off the system, and rebooting the system.

The user-defined runlevels are those with an accompanying /etc/runlevels/ subdirectory: boot, default, nonetwork and single. The boot runlevel starts all system-necessary services which all other runlevels use. The remaining three runlevels differ in what services they start: default is used for day-to-day operations, nonetwork is used in case no network connectivity is required, and single is used when the system needs to be fixed.

Trabalhando com initscripts

The scripts that the openrc process starts are called init scripts. Each script in /etc/init.d/ can be executed with the arguments start, stop, restart, zap, status, ineed, iuse, iwant, needsme, usesme, or wantsme.

To start, stop, or restart a service (and all depending services), the start, stop, and restart arguments should be used:

root #rc-service postfix start

Nota
Only the services that need the given service are stopped or restarted. The other depending services (those that use the service but don't need it) are left untouched.

To stop a service, but not the services that depend on it, use the --nodeps option together with the stop argument:

root #/etc/init.d/postfix --nodeps stop

Para ver o status de um serviço (executando, parado, ...), use o argumento status:

root #/etc/init.d/postfix status

If the status information shows that the service is running, but in reality it is not, then reset the status information to "stopped" with the zap argument:

root #rc-service postfix zap

To also ask what dependencies the service has, use iwant, iuse or ineed. With ineed it is possible to see the services that are really necessary for the correct functioning of the service. iwant or iuse, on the other hand, shows the services that can be used by the service, but are not necessary for the correct functioning.

root #rc-service postfix ineed

Similarly, it is possible to ask what services require the service (needsme) or can use it (usesme or wantsme):

root #rc-service postfix needsme

Updating runlevels

rc-update

Gentoo's init system uses a dependency-tree to decide what service needs to be started first. As this is a tedious task that we wouldn't want our users to have to do manually, we have created tools that ease the administration of the runlevels and init scripts.

With rc-update it is possible to add and remove init scripts to a runlevel. The rc-update tool will then automatically ask the depscan.sh script to rebuild the dependency tree.

Adding and removing services

In earlier instructions, init scripts have already been added to the "default" runlevel. What "default" means has been explained earlier in this document. Next to the runlevel, the rc-update script requires a second argument that defines the action: add, del, or show.

To add or remove an init script, just give rc-update the add or del argument, followed by the init script and the runlevel. For instance:

root #rc-update del postfix default

The rc-update -v show command will show all the available init scripts and list at which runlevels they will execute:

root #rc-update -v show

It is also possible to run rc-update show (without -v) to just view enabled init scripts and their runlevels.

Configuring services

Why additional configuration is needed

Init scripts can be quite complex. It is therefore not really desirable to have the users edit the init script directly, as it would make it more error-prone. It is however important to be able to configure such a service. For instance, users might want to give more options to the service itself.

A second reason to have this configuration outside the init script is to be able to update the init scripts without the fear that the user's configuration changes will be undone.

conf.d directory

Gentoo provides an easy way to configure such a service: every init script that can be configured has a file in /etc/conf.d/. For instance, the apache2 initscript (called /etc/init.d/apache2) has a configuration file called /etc/conf.d/apache2, which can contain the options to give to the Apache 2 server when it is started:

FILE /etc/conf.d/apache2Example options for apache2 init script

APACHE2_OPTS="-D PHP5"

Such a configuration file contains only variables (just like /etc/portage/make.conf does), making it very easy to configure services. It also allows us to provide more information about the variables (as comments).

Writing initscripts

Another useful resource is OpenRC's service script guide.

Is it necessary?

No, writing an init script is usually not necessary as Gentoo provides ready-to-use init scripts for all provided services. However, some users might have installed a service without using Portage, in which case they will most likely have to create an init script.

Do not use the init script provided by the service if it isn't explicitly written for Gentoo: Gentoo's init scripts are not compatible with the init scripts used by other distributions! That is, unless the other distribution is using OpenRC!

Layout

The basic layout of an init script is shown below.

CODE Example initscript layout (traditional)

#!/sbin/openrc-run
  
depend() {
#  (Dependency information)
}
  
start() {
#  (Commands necessary to start the service)
}
  
stop() {
#  (Commands necessary to stop the service)
}

CODE Example initscript layout (updated)

#!/sbin/openrc-run
command=/usr/bin/foo
command_args="${foo_args} --bar"
pidfile=/var/run/foo.pid
name="FooBar Daemon"
 
description="FooBar is a daemon that drinks"
extra_started_commands="drink"
description_drink="Opens mouth and reflexively swallows"
 
depend() {
#  (Dependency information)
}
 
start_pre() {
#  (Commands necessary to prepare to start the service)
    # Ensure that our dirs are correct
    checkpath --directory --owner foo:foo --mode 0775 \
        /var/run/foo /var/cache/foo
}
  
stop_post() {
#  (Commands necessary to clean up after the service)
    # Clean any spills
    rm -rf /var/cache/foo/*
}
 
drink() {
    ebegin "Starting to drink"
    ${command} --drink beer
    eend $? "Failed to drink any beer :("
}

Every init script requires the start() function or command variable to be defined. All other sections are optional.

Dependencies

There are three dependency-alike settings that can be defined which influence the start-up or sequencing of init scripts: want, use and need. Next to these, there are also two order-influencing methods called before and after. These last two are no dependencies per se - they do not make the original init script fail if the selected one isn't scheduled to start (or fails to start).

• The use settings informs the init system that this script uses functionality offered by the selected script, but does not directly depend on it. A good example would be use logger or use dns. If those services are available, they will be put in good use, but if the system does not have a logger or DNS server the services will still work. If the services exist, then they are started before the script that uses them.
• The want setting is similar to use with one exception. use only considers services which were added to an init level. want will try to start any available service even if not added to an init level.
• The need setting is a hard dependency. It means that the script that is needing another script will not start before the other script is launched successfully. Also, if that other script is restarted, then this one will be restarted as well.
• When using before, then the given script is launched before the selected one if the selected one is part of the init level. So an init script xdm that defines before alsasound will start before the alsasound script, but only if alsasound is scheduled to start as well in the same init level. If alsasound is not scheduled to start too, then this particular setting has no effect and xdm will be started when the init system deems it most appropriate.
• Similarly, after informs the init system that the given script should be launched after the selected one if the selected one is part of the init level. If not, then the setting has no effect and the script will be launched by the init system when it deems it most appropriate.

It should be clear from the above that need is the only "true" dependency setting as it affects if the script will be started or not. All the others are merely pointers towards the init system to clarify in which order scripts can be (or should be) launched.

Now, look at many of Gentoo's available init scripts and notice that some have dependencies on things that are no init scripts. These "things" we call virtuals.

A virtual dependency is a dependency that a service provides, but that is not provided solely by that service. An init script can depend on a system logger, but there are many system loggers available (metalogd, syslog-ng, sysklogd, ...). As the script cannot need every single one of them (no sensible system has all these system loggers installed and running) we made sure that all these services provide a virtual dependency.

For instance, take a look at the postfix dependency information:

FILE /etc/init.d/postfixDependency information of the postfix service

depend() {
  need net
  use logger dns
  provide mta
}

As can be seen, the postfix service:

• Requires the (virtual) net dependency (which is provided by, for instance, /etc/init.d/net.eth0).
• Uses the (virtual) logger dependency (which is provided by, for instance, /etc/init.d/syslog-ng).
• Uses the (virtual) dns dependency (which is provided by, for instance, /etc/init.d/named).
• Provides the (virtual) mta dependency (which is common for all mail servers).

Controlling the order

As described in the previous section, it is possible to tell the init system what order it should use for starting (or stopping) scripts. This ordering is handled both through the dependency settings use and need, but also through the order settings before and after. As we have described these earlier already, let's take a look at the portmap service as an example of such init script.

FILE /etc/init.d/portmapDependency information of the portmap service

depend() {
  need net
  before inetd
  before xinetd
}

It is possible to use the "*" glob to catch all services in the same runlevel, although this isn't advisable.

CODE Using the * glob

depend() {
  before *
}

If the service must write to local disks, it should need localmount. If it places anything in /var/run/ such as a PID file, then it should start after bootmisc:

CODE Dependency setting with needing localmount and after bootmisc

depend() {
  need localmount
  after bootmisc
}

Standard functions

Next to the depend() functionality, it is also necessary to define the start() function. This one contains all the commands necessary to initialize the service. It is advisable to use the ebegin and eend functions to inform the user about what is happening:

CODE Example start() function

start() {
  if [ "${RC_CMD}" = "restart" ];
  then
    # Do something in case a restart requires more than stop, start
  fi
  
  ebegin "Starting my_service"
  start-stop-daemon --start --exec /path/to/my_service \
    --pidfile /path/to/my_pidfile
  eend $?
}

Both --exec and --pidfile should be used in start and stop functions. If the service does not create a pidfile, then use --make-pidfile if possible, though it is recommended to test this to be sure. Otherwise, don't use pidfiles. It is also possible to add --quiet to the start-stop-daemon options, but this is not recommended unless the service is extremely verbose. Using --quiet may hinder debugging if the service fails to start.

Another notable setting used in the above example is to check the contents of the RC_CMD variable. Unlike the previous init script system, the newer OpenRC system does not support script-specific restart functionality. Instead, the script needs to check the contents of the RC_CMD variable to see if a function (be it start() or stop()) is called as part of a restart or not.

Nota
Make sure that --exec actually calls a service and not just a shell script that launches services and exits - that's what the init script is supposed to do.

For more examples of the start() function, please read the source code of the available init scripts in the /etc/init.d/ directory.

Another function that can (but does not have to) be defined is stop(). The init system is intelligent enough to fill in this function by itself if start-stop-daemon is used.

CODE Example stop() function

stop() {
  ebegin "Stopping my_service"
  start-stop-daemon --stop --exec /path/to/my_service \
    --pidfile /path/to/my_pidfile
  eend $?
}

If the service runs some other script (for example, Bash, Python, or Perl), and this script later changes names (for example, foo.py to foo), then it is necessary to add --name to start-stop-daemon. This must specify the name that the script will be changed to. In this example, a service starts foo.py, which changes names to foo:

CODE Example definition for a service that starts the foo script

start() {
  ebegin "Starting my_script"
  start-stop-daemon --start --exec /path/to/my_script \
    --pidfile /path/to/my_pidfile --name foo
  eend $?
}

start-stop-daemon has an excellent man page available if more information is needed:

user $man start-stop-daemon

Gentoo's init script syntax is based on the POSIX Shell so people are free to use sh-compatible constructs inside their init scripts. Keep other constructs, like bash-specific ones, out of the init scripts to ensure that the scripts remain functional regardless of the change Gentoo might do on its init system.

Adding custom options

If the initscript needs to support more options than the ones we have already encountered, then add the option to one of the following variables, and create a function with the same name as the option. For instance, to support an option called restartdelay:

• extra_commands - Command is available with the service in any state
• extra_started_commands - Command is available when the service is started
• extra_stopped_commands - Command is available when the service is stopped

CODE Example definition of restartdelay method

extra_started_commands="restartdelay"
  
restartdelay() {
  stop
  sleep 3    # Wait 3 seconds before starting again
  start
}

Importante
The restart() function cannot be overridden in OpenRC!

Service configuration variables

In order to support configuration files in /etc/conf.d/, no specifics need to be implemented: when the init script is executed, the following files are automatically sourced (i.e. the variables are available to use):

• /etc/conf.d/YOUR_INIT_SCRIPT
• /etc/conf.d/basic
• /etc/rc.conf

Also, if the init script provides a virtual dependency (such as net), the file associated with that dependency (such as /etc/conf.d/net) will be sourced too.

Changing runlevel behavior

Who might benefit

Many laptop users know the situation: at home they need to start net.eth0, but they don't want to start net.eth0 while on the road (as there is no network available). With Gentoo the runlevel behavior can be altered at will.

For instance, a second "default" runlevel can be created which can be booted that has other init scripts assigned to it. At boot time, the user can then select what default runlevel to use.

Using softlevel

First of all, create the runlevel directory for the second "default" runlevel. As an example we create the offline runlevel:

root #mkdir /etc/runlevels/offline

Add the necessary init scripts to the newly created runlevel. For instance, to have an exact copy of the current default runlevel but without net.eth0:

root #cd /etc/runlevels/default

root #for service in *; do rc-update add $service offline; done

root #rc-update del net.eth0 offline

root #rc-update show offline

(Partial sample Output)
               acpid | offline
          domainname | offline
               local | offline
            net.eth0 |

Even though net.eth0 has been removed from the offline runlevel, udev might want to attempt to start any devices it detects and launch the appropriate services, a functionality that is called hotplugging. By default, Gentoo does not enable hotplugging.

To enable hotplugging, but only for a selected set of scripts, use the rc_hotplug variable in /etc/rc.conf:

FILE /etc/rc.confEnable hotplugging of the WLAN interface

rc_hotplug="net.wlan !net.*"

Nota
For more information on device initiated services, please see the comments inside /etc/rc.conf.

Edit the bootloader configuration and add a new entry for the offline runlevel. In that entry, add softlevel=offline as a boot parameter.

Using bootlevel

Using bootlevel is completely analogous to softlevel. The only difference here is that a second "boot" runlevel is defined instead of a second "default" runlevel.

Variáveis de ambiente

Introdução

Uma variável de ambiente é um objeto com nome que contém informações utilizadas por uma ou mais aplicações. Usando variáveis de ambiente pode-se facilmente alterar configurações para uma ou mais aplicações.

Exemplos Importantes

A tabela a seguir lista algumas das variáveis utilizadas por um sistema Linux e descreve seus usos. Exemplos de valores são apresentados após a tabela.

Variable	Description
PATH	This variable contains a colon-separated list of directories in which the system looks for executable files. If a name is entered of an executable (such as ls, rc-update, or emerge) but this executable is not located in a listed directory, then the system will not execute it (unless the full path is entered as the command, such as /bin/ls).
ROOTPATH	This variable has the same function as PATH, but this one only lists the directories that should be checked when the root-user enters a command.
LDPATH	This variable contains a colon-separated list of directories which the dynamic linker searches to find a library.
MANPATH	This variable contains a colon-separated list of directories which the man(1) command searches for man pages.
INFODIR	This variable contains a colon-separated list of directories which the info(1) command searches for info pages.
PAGER	This variable contains the path to the program used to list the contents of files (such as less or more(1)).
EDITOR	This variable contains the path to the program used to edit files (such as nano or vi).
KDEDIRS	This variable contains a colon-separated list of directories which contain KDE-specific material.
CONFIG_PROTECT	This variable contains a space-delimited list of directories which should be protected by Portage during package updates.
CONFIG_PROTECT_MASK	This variable contains a space-delimited list of directories which should not be protected by Portage during package updates.

Below is an example definition of all these variables:

CODE Example settings for the mentioned variables

PATH="/bin:/usr/bin:/usr/local/bin:/opt/bin:/usr/games/bin"
ROOTPATH="/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin"
LDPATH="/lib:/usr/lib:/usr/local/lib:/usr/lib/gcc-lib/i686-pc-linux-gnu/3.2.3"
MANPATH="/usr/share/man:/usr/local/share/man"
INFODIR="/usr/share/info:/usr/local/share/info"
PAGER="/usr/bin/less"
EDITOR="/usr/bin/vim"
KDEDIRS="/usr"
# Directories that are protected during package updates.
# Note the use of the \ (backslashes) on the end of the following lines which interprets to a single space-delimited line.
CONFIG_PROTECT="/usr/X11R6/lib/X11/xkb /opt/tomcat/conf \
                /usr/kde/3.1/share/config /usr/share/texmf/tex/generic/config/ \
                /usr/share/texmf/tex/platex/config/ /usr/share/config"
# Directories that are _not_ protected during package updates.
CONFIG_PROTECT_MASK="/etc/gconf"

Defining variables globally

O diretório env.d

To centralize the definitions of these variables, Gentoo introduced the /etc/env.d/ directory. Inside this directory a number of files are available, such as 50baselayout, gcc/config-x86_64-pc-linux-gnu, etc. which contain the variables needed by the application mentioned in their name.

For instance, when gcc is installed, a file called gcc/config-x86_64-pc-linux-gnu was created by the ebuild which contains the definitions of the following variables:

FILE /etc/env.d/gcc/config-x86_64-pc-linux-gnuDefault gcc enabled environment variables for GCC 13

GCC_PATH="/usr/x86_64-pc-linux-gnu/gcc-bin/13"
LDPATH="/usr/lib/gcc/x86_64-pc-linux-gnu/13:/usr/lib/gcc/x86_64-pc-linux-gnu/13/32"
MANPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/13/man"
INFOPATH="/usr/share/gcc-data/x86_64-pc-linux-gnu/13/info"
STDCXX_INCDIR="g++-v13"
CTARGET="x86_64-pc-linux-gnu"
GCC_SPECS=""
MULTIOSDIRS="../lib64:../lib"

Other distributions might tell the system administrator to change or add such environment variable definitions in /etc/profile or other locations. Gentoo on the other hand makes it easy for the sysadmins (and for Portage) to maintain and manage the environment variables without having to pay attention to the numerous files that can contain environment variables.

For instance, when gcc is updated, the associated file(s) under /etc/env.d/gcc are updated too without requesting any administrative interaction.

There are still occasions where a system administrator is asked to set a certain environment variable system-wide. As an example, take the http_proxy variable. Instead of editing a file under the /etc/profile directory, create a file named /etc/env.d/99local and enter the definition in it:

FILE /etc/env.d/99localSetting a global environment variable

http_proxy="proxy.server.com:8080"

By using the same file for all customized environment variables, system administrators have a quick overview on the variables they have defined themselves.

env-update

Several files within the /etc/env.d directory add definitions to the PATH variable. This is not a mistake: when the env-update command is executed, it will append the several definitions before it atomically updates each environment variable, thereby making it easy for packages (or system administrators) to add their own environment variable settings without interfering with the already existing values.

The env-update script will append the values in the alphabetical order of the /etc/env.d/ files. The file names must begin with two decimal digits.

CODE Update order used by env-update

09sandbox    50baselayout     51dconf
     +------------+----------------+-----------+
CONFIG_PROTECT_MASK="/etc/sandbox.d /etc/gentoo-release /etc/dconf ..."

The concatenation of variables does not always happen, only with the following variables: ADA_INCLUDE_PATH, ADA_OBJECTS_PATH, CLASSPATH, KDEDIRS, PATH, LDPATH, MANPATH, INFODIR, INFOPATH, ROOTPATH, CONFIG_PROTECT, CONFIG_PROTECT_MASK, PRELINK_PATH, PRELINK_PATH_MASK, PKG_CONFIG_PATH, and PYTHONPATH. For all other variables the latest defined value (in alphabetical order of the files in /etc/env.d/) is used.

It is possible to add more variables into this list of concatenate-variables by adding the variable name to either COLON_SEPARATED or SPACE_SEPARATED variables (also inside an /etc/env.d/ file).

When executing env-update, the script will create all environment variables and place them in /etc/profile.env (which is used by /etc/profile). It will also extract the information from the LDPATH variable and use that to create /etc/ld.so.conf. After this, it will run ldconfig to recreate the /etc/ld.so.cache file used by the dynamical linker.

To notice the effect of env-update immediately after running it, execute the following command to update the environment. Users who have installed Gentoo themselves will probably remember this from the installation instructions:

root #env-update && source /etc/profile

Nota
The above command only updates the variables in the current terminal, new consoles, and their children. Thus, if the user is working in X11, he needs to either type source /etc/profile in every new terminal opened or restart X so that all new terminals source the new variables. If a login manager is used, it is necessary to become root and restart the /etc/init.d/xdm service.

Importante
It is not possible to use shell variables when defining other variables. This means things like FOO="$BAR" (where $BAR is another variable) are forbidden.

Defining variables locally

User specific

It might not be necessary to define an environment variable globally. For instance, one might want to add /home/my_user/bin and the current working directory (the directory the user is in) to the PATH variable but not want all other users on the system to have those directories in their PATH. To define an environment variable locally, use ~/.bashrc (for all interactive shell sessions) or ~/.bash_profile (for login shell sessions):

FILE ~/.bashrcExtending PATH for local usage

# A colon followed by no directory is treated as the current working directory
PATH="${PATH}:/home/my_user/bin:"

After logout/login, the PATH variable will be updated.

Session specific

Sometimes even stricter definitions are required. For instance, a user might want to be able to use binaries from a temporary directory without needing to use the full path to the binaries and without needing to temporarily change ~/.bashrc.

In this case, just define the PATH variable in the current session by using the export command. As long as the user does not log out, the PATH variable will be using the temporary settings.

root #export PATH="${PATH}:/home/my_user/tmp/usr/bin"